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  • HPH383: A beginner’s guide to creating a comfortable home – with Andy Mitchell

    HPH383: A beginner’s guide to creating a comfortable home – with Andy Mitchell

    Andy Mitchell, Managing Director of 21 Degrees, explains what factors influence human comfort and how we have tried to make our homes more comfortable through the years. Embracing building physics has been a turning point and while we have the knowledge and skills to create healthy and comfortable homes today, it’s still not the default approach. So Andy outlines the options available to get yourself into a better home.

    Interview with Andy Mitchell

    Andy Mitchell is the Managing Director of 21 Degrees. Engineering runs in the blood as he comes from a family of engineers and he has always been fascinated by houses and buildings, even considering architecture as a possible career path at one stage. Studying product design at A-Level he then became interested in company structure and business. His first significant role in sustainability was at a company called Natural Building Technologies in the early 2000s, where there was a focus on healthy bio-based materials. Today he heads up 21 Degrees, a company which supplies key technology to homeowners and architects enabling them to build more efficiently, and generate and store energy.

    In this podcast Andy explores the concept of comfort and explains why we can do much better when it comes to creating a comfortable and healthy home in which to thrive.

    We can define a comfortable temperature

    While we might think that we are all different and therefore prefer to live at different temperatures, that is not true. We can define a comfortable temperature range because of our physiology.

    “Any human being, no matter where they are on the planet is most comfortable between 20°C to 22°C. The reason is simple. If the temperature is higher, your body has to work harder to keep you cool; and if it’s colder, your body has to work harder to keep warm.”

    The body doesn’t cope well under 15°C

    Below 15°C humans have to work hard to keep warm. At 9°C or less, it’s a matter of survival.

    How active we are, alters what we perceive as a comfortable temperature

    If we’re engaging in a lot of activity, such as cleaning our homes, we are generating heat and keeping ourselves warm, so may desire a cooler temperature. Alternatively, if we are working at a desk and sedentary then the reverse is true and we may want it to be warmer. Generally speaking the impact of this is plus or minus 2°C.

    Putting on clothes is another dynamic

    You only need to look to the Inuit in parts of Greenland to understand what an impact clothing can have. They could survive in subzero temperatures. The downside is that their clothing was bulky and would limit the activities they could perform. Any clothing will go some way to making us feel warmer because it’s trapping the body’s heat and slowing it down from moving away from the body. It would be the same effect sleeping under a duvet. The duvet is insulating your body heat.

    Relative humidity levels impact our health and comfort

    Humidity, or the level of moisture that’s in the air relative to the temperature, has an impact on comfort. The warmer the air, the more moisture the air can hold. And generally, humans are most comfortable at 50%, plus or minus 5%. It’s quite hard to fix humidity levels but between 40-60% is seen as a healthy range. If the levels exceed 70% regularly then these conditions can lead to damp and mould, which are damaging to human health. Below 40% is not good either and could cause respiratory issues.

    Lowering the temperature to save money will create an unhealthy environment

    Andy explains that it may be a false economy to turn down the thermostat in winter to save money or reduce fossil fuel usage. This is because as you drop the temperature the relative humidity goes up.

    “If you had a temperature of 22°C and the relative humidity was 50%, and you dial the temperature down to 18°C, you’ll actually increase the relative humidity to 64%… You’ve made yourself slightly more uncomfortable because you’ve increased the relative humidity.”

    With poor ventilation, which is common in many British homes, the relative humidity may have been closer to 55% anyway.

    “If we’re closer to 55% relative humidity that really starts to get interesting, because if you dial down from 22°C to 18°C, you’re at 73% relative humidity and that starts affecting your health. For example, dust mites proliferate above 70%, eczema and asthma are a direct consequence of allergic reactions to dust mite poop. You’ve also got issues with mould growth.”

    Radiant heat also plays its part in comfort

    In addition to temperature and humidity, radiant heat plays a significant role in how comfortable we feel. Andy shares a couple of examples of when you might have experienced this.

    If you’re taking a stroll on a sunny day and a cloud goes in front of the sun, you might notice you suddenly feel a bit cold. The air temperature hasn’t changed. What’s happened is the radiant heat that’s been hitting your body has dropped because it’s been obscured by the cloud.

    Radiant heat is also absorbed and emitted by surfaces in our homes such as furnishings, walls, windows, etc. So the temperature of those surfaces will have a significant impact on your comfort levels.

    Our homes have got better over time!

    Over the centuries we have turned to fires to keep us warm. In Victorian times there were open fires, which were extremely inefficient because most of the heat went straight up the chimney. However, the rooms felt more comfortable because of the radiant heat being absorbed and then given off from walls and furnishings, etc.

    “The big, winged armchairs that we perhaps thought were to stop granddad falling out of his chair when he fell asleep were actually to keep the radiant heat in… It captured that heat that was being radiated out from the fireplace in the room.”

    With the advent of cheap energy, such as access to North Sea gas in the UK, we could pipe fuel straight into our houses. Burning this in boilers, heating water and then piping it around radiators was a big leap forwards. Although fossil fuels are energy dense and have been an easy source of fuel, their emissions have contributed to global warming and we have nearly exhausted the supply in a few decades. 

    Indoor temperatures have been increasing

    Back in the 1970s, the average temperature in a British house in winter was 12°C – 13°C. These days, it’s probably closer to 18°C – 19°C. Andy says that figure could be impacted by a number of people who are in genuine fuel poverty. In other words, they find it unaffordable to heat their homes. One reason for this is that the UK has a large amount of old and leaky properties.

    Leaky homes are just about tolerable in a mild climate

    Andy says that the UK has the most inefficient housing stock in Europe. While Germany is on a latitude further South and might face temperatures of -10°C, a British winter is milder and more akin with Italy. Therefore with a few token measures, such as double glazing, and cheap energy, we have got by.

    “Sadly, I think we focus more on basic survival and then toleration, rather than what makes for a great home? What really does give us that extra level above survival, so that we can thrive? Again, to me, this is very much what comfort brings… It means you can be more productive in terms of your work. You’ve got higher levels of energy, because you’re not using it to keep yourself warm or cooler.”

    Sensing a ‘muggy’ environment indicates pollutants have built up

    As we live in our homes the indoor air is changing. We exhale CO2 and generate moisture from our activities. Relative humidity builds up and there may even be VOCs given off from furniture, paints, etc. Our instinct is to open a window, which Andy says will solve the problem.

    “By opening the window, you purge the air to the outside, because generally warm air will move to the outside, particularly if there’s a bit of cross ventilation, and as a result, arguably, the temperature will be dropping a bit. But if you don’t leave that window open for too long you’ll have a complete air change, and the air that’s come into that room, because the walls and the fabric are warm, to some extent, that air will warm up. And what was outside air, which was probably around about 70% relative humidity, would have dropped down to around about 50% relative humidity, and suddenly you feel much better again!”

    The problem is this purge is needed regularly and is hard to manage. More often than not there will be a drop in internal temperature.

    In winter another source of discomfort is draughts, where you’re sensing changes in air temperature. For example, if you stand near windows that are single or double glazed, they are colder than the internal air temperature so you will feel the heat moving away from your body.

    You may also experience stratification of the air and this heat differential causes air movement, which in turn can make you feel uncomfortable. For example, your feet can feel colder than your torso. You may not even be aware of it.

    We have got to grips with the physics of buildings and know how to build better homes

    In the past we have simply put our buildings together without worrying too much about how effective they are, focusing more on aesthetics. However, there is an approach that works and has been around for over thirty years. Dr Wolfgang Feist and the team at the Passive House Institute decided to look at things from the first principles and get a holistic picture. This led to the development of the Passivhaus standard, which is a formula that anyone can follow to make a building that works. Core principles include insulation, airtightness, high performance components such as windows and doors, reducing or eliminating thermal bridges, introducing mechanical ventilation with heat recovery, and orientating the building towards the sun.

    Andy points out some of the benefits. For example, in a Passivhaus the temperature of the surfaces will be plus or minus 3°C of the air temperature. It will be draught-free and the heat loss will have been reduced significantly. The introduction of mechanical ventilation with heat recovery also means there’s constant fresh air coming into the building, but the heat from the outgoing stale air is retained. And this is a way of controlling the relative humidity, too.

    So building or buying a certified Passivhaus is one way of ensuring you have a comfortable and healthy home.

    Buying a new home doesn’t necessarily mean it’ll be efficient or healthy

    Although the Passivhaus standard was developed decades ago, the learnings and methodology have not been incorporated into the building regulations. Therefore there is still a performance gap in most new buildings, where the design intent is never reached in the completed building.

    We are all responsible for the status quo

    Not only do we as homeowners tend to accept the status quo rather than demanding higher standards, but architects, designers and contractors struggle to adopt new strategies. So sometimes the drawings fail to give enough detail, particularly around things like airtightness or thermal bridging, which is just where you’ve got surfaces or materials joining together, and you can get additional heat loss that you wouldn’t do through the principal wall or roof or floor areas. It can be the contractors on site, who don’t fully understand the goals of the project and might cut through a membrane not realising the impact of doing this.

    Then there’s the building standards themselves. The reality is the building standards stop at the point of design. Currently there is no ‘as-built’ check of the performance.

    “So the performance standard stops at the design stage because you demonstrate through something called SAP, Standard Assessment Procedure, what is the heat loss from this building based on the building fabric. It’s pushed through a calculation. Effectively, it says yes this fabric will pass, and that’s where the testing ends. There is nobody from Building Control actually measuring the heat loss of the building once it’s occupied.”

    The choices are getting better

    Andy believes that building to a performance standard above and beyond building regulations is becoming more common. We’ve mentioned the Passivhaus standard but there’s also the retrofit standard EnerPHit. The AECB New Build standard is another option, which is slightly easier to reach, but has the same rigorous building physics approach.

    Building your own home allows you to get what you want

    When people are building or commissioning their own homes they almost always strive for higher standards. And doing a self-build project is not quite as onerous as it might seem, with more and more help available. Andy says we build about 5% of our homes in the UK this way, or 15,000 homes a year, which is equivalent to the output of the fourth largest volume house-builder in the UK. This is a good start but to put it into perspective Germany deliver around 50% of their homes as self-build. So maybe it’s not surprising that these standards have taken time to be adopted.

    It is possible to improve the performance of an existing property

    If building new or buying from the open market is not proving successful, then there is another option. Existing homes can be retrofitted to a performance standard. It is often harder, and some homes will be more challenging than others. For example, how the building is orientated is something that is hard to change. There are also significant costs for a deep retrofit.

    “The more complex a building is in its form, often the more challenging it is to reduce the heating requirement, the heat load. You can still go a long way, though, to improve airtightness and therefore comfort levels but you might not achieve the same low energy results that other more simpler forms of building can.”

    On a phased retrofit, improve the ventilation first

    Doing a retrofit in one hit often makes life easier, but not everybody is in a position to do this. So another option is to do a phased retrofit. The most important part is to have a comprehensive whole house plan at the beginning.

    Andy says that a good first step is to improve the ventilation of a property because that will give you cleaner, fresher air, with more controlled levels of relative humidity. While it may cost a bit more in heating initially until you have reduced your heat loss, you can immediately benefit and also reduce the risk of damp and mould building up in places where you have improved the fabric but have not improved the ventilation yet.

    The average family home produces up to as much as 15 litres of moisture a day that goes into the air. This evaporates from our bodies when we’re sleeping or walking around the house. Moisture is also generated when we’re cooking, taking a shower or doing the washing, and it has to go somewhere.

    So after the ventilation has been addressed, the next phase might be looking at improving the airtightness and replacing the windows.

    Adding insulation changes the physics of the building

    When you apply products to your building, you are changing the physics of the building. So if you apply a piece of insulation to a part of your property, you are changing what was there before, and if it hasn’t been well thought through you could end up with unintended consequences. Andy gives an example of fitting closed cell insulation internally which is principally a bad idea because you are likely to trap moisture in the wall. This interstitial condensation could ultimately lead to the building fabric being damaged or breaking down, or potentially creating mould pockets, which then can affect the quality of the air in the room.

    Mechanical ventilation must be designed well

    There are various ducted ventilation systems on the market but they have to be designed well to be effective.

    “The ducting design, for example, in MVHR is far more important than the actual unit that you plug into the end of it. A decent fan and heat exchanger is important, but you can have the best MVHR unit on the market and you plug it into poor ducting design, and you’ll just have a poor system. Whereas you could have an average MVHR unit and plug it into some effectively designed ducting, and you’d have actually a very good system.”

    MVHR can be useful if the outdoor air is not clean

    If the external air quality is poor, such as on a busy road, or if there’s a lot of pollen that is having a particularly bad effect on a hayfever sufferer then a fully vented, ducted system often takes the air through filters. So you can filter particulates from outside and stop them coming into the house.

    Making a home more healthy and comfortable shouldn’t be about payback

    When people go on holiday they don’t look for the payback on their holiday! People are also prepared to spend a lot of money on a kitchen. However, when you tackle a big project that will improve health and save money on bills, they suddenly believe it should pay for itself.

    Treat homes as homes, not as assets

    It would be good if we moved away from viewing houses as assets, and actually looked at them as a way to help us live effectively.

    Andy is tackling his own retrofit

    We are all on a journey to creating better homes for ourselves and our families. And that includes Andy! He is making improvements to his Victorian home with a phased approach.

    “You do a measure to your own property, and you still find yourself being quite impressed! So we live in a Victorian property, and half of the floor of the property is a cellar. The other half is solid floor, and we insulated in the joists of effectively the cellar part, and that made a significant improvement. And then the following year, we had an airtightness membrane installed underneath the joist and the insulation, and that made as significant, if not more significant an improvement in both the thermal performance of that room.”

    Andy believes that most of us become complacent with our homes when we actually have the opportunity to enhance our lives.

    “As human beings, we have this incredible gift of adaptation. The problem is it’s also a curse, and we just tolerate an awful lot of rubbish. If our awareness was increased and we could begin to learn what is possible, particularly in terms of how we can live within our built environment I think the change for our welfare, both as individuals and society in general, would be significantly impactful.”

    Find out more

    21 Degrees

    Why MVHR maintenance and servicing is important

    What makes a well designed MVHR system?

    How do you specify high performance windows?

    Two radical retrofits that use an internal wall insulation strategy

    Low energy barn conversions

    Transcript

    Download a transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

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  • HPH382: What is a Principal Designer? – with Ben Nother

    HPH382: What is a Principal Designer? – with Ben Nother

    Ben Nother, a Director at Hawkland Group, explains the two different roles of Principal Designer in meeting building regulations and addressing CDM health and safety. He also reflects on how this has been integrated into their processes.

    Interview with Ben Nother

    Ben Nother comes from a family of builders and bricklayers, and this is exactly where he started, on site as a labourer working on different construction projects during his teenage years. He was then encouraged to go into the professional side of the industry and chose architecture, studying at both the University of the West of England and then the Centre for Alternative Technology. This allowed him to delve into sustainability issues and the challenges of climate change. After 5 years working for different practices, he became freelance to find a better work life balance. Gradually he developed a good working relationship with Hawkland Group, eventually joining their team as a director.

    In this conversation Ben is giving us his take on the Principal Designer role. For a more detailed explanation of the Principal Designer duties and responsibilities check out the guidance on Gov.uk.

    The role of Principal Designer has evolved

    Until recently a Principal Designer was the person who focused on meeting the Construction Design & Management regulations (CDM), from the Health and Safety Executive. Essentially, they would consider everything needed to ensure health and safety on a construction site. A Principal Designer would start with the design risks within a building project to see if they could be eliminated and if not, identify how the risks could be managed. For example, you may not want to design out a rooflight, so identify that there is going to be work at height, which is then a risk to be managed. A list of risks is given to a Principal Contractor who can put in place the relevant health and safety measures, such as scaffolding and the need for harnessing.

    CDM Principal Designer and Building Regulations Principal Designer

    Following the Grenfell tragedy, the Building Safety Act was revised in 2022, with all the regulations gradually coming into force by 2024. So there are two roles that fall under different legislation frameworks which both use the title Principal Designer.

    So, to reiterate, the two areas to be addressed are:

    • CDM health and safety.
    • Compliance with building regulations.

    The Principal Designer now takes on more responsibility and liability

    Before these changes, an architect would pull together drawings and information on thermal performance, fire safety, structural engineer’s calculations, everything needed to ensure it would meet the building regulations. These would then go to the local authority or an approved building inspector to be assessed and signed off. The new regulations have changed the responsibility chain, so the Principal Designer is now more liable for those building regulations and is now co-signing them off with approved building inspectors.

    As they are the designer of the building, they know what’s going into it, the performance that it should achieve, so have the responsibility that it will meet the building regulations. The Principal Designer will now also be doing site inspections to ensure that the builder has complied with the suggested interventions and will supply evidence for the building inspector. Architectural practices, structural engineers and others can provide this Principal Designer role.

    Different people may take on the role of Principal Designer during the project

    Today Hawkland Group has two brands: Hawkland Architects and Hawkland Construction. Historically, however, Hawkland was a contracting company. So clients often approach them post planning for input on the construction of a building. The client may have a full package of information that has been taken through to technical design. In which case the architect or the structural engineer working on the project, would be the Principal Designer, with Hawkland Construction, then taking on the Principal Contractor role. In other cases, Hawkland Architects may take on the design work from stage four, post planning, and so would take on the Principal Designer role as well. Under the new Building Safety Act, they would be looking for a comprehensive handover from the previous architectural practice or designer who has put together stage three, with all the identified risks and mitigation measures.

    Ben likes their approach at Hawkland Group, where they can take responsibility for a project from concept to completion, because they can put together a robust set of both CDM and building regulations information. Otherwise he’s working from someone else’s information, checking it, trying to fill in gaps for something already part designed. This could well mean a doubling up on time going through someone else’s designs and information.

    The Principal Designer role continues in the build phase

    The Principal Designer role continues through the build and as the person most familiar with all aspects of the build they will make sure that each company brought in is competent, has the relevant insurances and qualifications and that the design being put forward is compliant and safe.

     “…having a Principal Designer all the way through as one person is key, because they know all of the different moving parts on that project.”

    The client must understand who the Principal Designer is

    Under the CDM regulations, the client is ultimately responsible for health and safety on site, but they can shift those responsibilities to their Principal Contractor. The client protects themselves by bringing in people with the relevant qualifications and right insurances to deliver their project. At Hawkland Group, they may take the project to a weather-tight shell, with the client then overseeing other contractors and perhaps also doing some of the work themselves. In this instance, the client takes on the responsibilities under CDM and now the new Building Safety Act, with Hawkland Group providing the drawings and information up to the technical design stage. They can also sit in the background to provide ongoing support for the client as the project progresses. If a client is going to assume the Principal Designer role it’s really important that they have the skillset and knowledge to do this. There’s more advice at Gov.uk.

    For someone doing their own designs and planning to undertake the build themselves they are taking on both the responsibility for health and safety on site and meeting building regulations. They need to know the risks around the building site, be able to induct specialist contractors to the site and be aware of everyone working on site. Ben recommends getting advice on the processes needed on construction projects as well as having an architect sense-check the designs.  

    There’s more from Hawkland Group in The Hub. David and Chris give us an overview of how to convert a loft.

    There are multiple considerations for the materials and products being used

    There will be health and safety aspects to consider under CDM alongside performance issues to be met for the building regulations. For example, some modern methods of construction may require that wall panels be lifted with specialist gear under CDM. If a crane is required, that needs to be able to get safely onto the site. The building regulations will consider the performance of those materials from a structural or fire safety perspective. The company producing the materials should be able to provide evidence of how they meet the different regulations. At Hawkland Group, they sometimes use straw direct from farmers, which won’t have those classifications for each bale, but fire tests have been done to show how that material reacts with fire. There is a bank of information for many natural materials now being used in construction.

    Manufacturers generally have all the information you need for products

    Manufacturers will also have standard build-ups that they know meet the regulations providing you use the materials in the right way with suitable ancillary products. The information is available but needs to be collated for building regulations sign-off. There are also instances of chemicals that need specialist handling and safe storage on site. An architectural practice will go through the specification process early on, so they know what needs to be done on site for health and safety, and what needs to be evidenced with building regulations.  

    The regulations should be front of mind from the outset

    Ben is now considering health and safety issues and building regulations as early as possible. If a client comes to him for example wanting a balcony, he will immediately look at the regulations around this. How high does the balustrading need to be, how high is the balcony off the ground, can it be a fire escape route? It’s important to look at this straight away as it may impact the designs across the rest of the building and it will need to meet building regulations. In the past something may have been designed for planning with no real consideration of how it was going to be built. Ben now has those conversations straight away and will know what products he wants to use from the concept design stage.

    The welfare of your build team is important

    Hawkland Group takes pride in their sites having good working conditions, being safe and inclusive. For example, the staff toilet could be a portable potty 20 metres away from the building where you have to brave the elements or it could be part of a comfortable staff welfare unit. On smaller jobs this might not be possible because space is tight and in Bristol, where they often work, sometimes their clients offer a room for them to use. Their site team also usually work four slightly longer days each week to give them a three day weekend and a bit of flexibility.

    A client can intervene if they are not happy with health and safety measures on site

    As a client you have a responsibility to raise concerns if you see that things could go wrong on site. It’s best to raise any issues with the contractor immediately and whilst they are responsible for Health and Safety on site you are well within your rights to challenge their approach and tell them they are not meeting CDM regulations. Hopefully they will be keen to adjust their way of working because there are significant penalties for not working safely. You could also raise it with your Principal Designer, for them to follow up. In a worst case scenario you could even terminate the contract, but this will leave you with some major challenges.  

    Hawkland Construction and many other contracting companies will have a site manager who is overseeing health and safety during the construction phase. Everyone is responsible for health and safety on site, but the project manager will help with regular inspections to see that everything is working well. It is also good practice to vet different companies beforehand, maybe visit a site they’re working on so you can see how they operate, not just a finished project. Checking they have the correct insurance cover is also important.

    There are advantages to having one principal designer for both CDM and building regulations

    For Ben it makes sense for one person to be responsible for both CDM and the building regulations. Whilst they cover slightly different aspects of the build they do go hand-in-hand. The Building Safety Act as part of its legislation, says the Principal Designer must be a designer, so ultimately it will an architect, or possibly a structural engineer. Ben explains that all the other designers on a project have to agree that the person appointed as the Principal Designer is competent to do this role. Under CDM, you can still use other companies to provide an independent Principal Designer role, so maybe a specialist health and safety company to support this aspect of the build. For a self-builder this could provide valuable support and technical information that you may not be familiar with.

    “The processes for building regulations and CDM are complicated. It’s really hard just to do it by yourself… it’s key in bringing in competent companies and competent individuals to be able to help you deliver your project.”

    Using one company for the whole project can simplify things for the client

    Whilst Hawkland Group can come in at any stage of the design or build process they also offer a complete service, where they deliver a whole project from start to finish. By overseeing the whole design process and technical phase of the build or retrofit there is then an ease of transition into the construction phase.

    Ben feels that this allows for continuity and good communication with the client and with everyone working on the project. The architectural team and construction team work closely together so that when it comes to pricing up for construction everyone is aware of the design and has been considering the type of build and looking at budget feasibility assessments throughout. Being very open with a client allows a better flow of information and can help achieve quicker decisions when things need to change during a build. It also allows for earlier investigative work to understand the type of issues that may come up, so you can be proactive rather than reactive.

    Find out more

    Hawkland Group

    Hawkland Architects

    Hawkland Construction

    Transcript

    Download a transcript of this episode.

    Subscribe to our YouTube channel

    Have you subscribed to our YouTube channel? Well, it’s a good way to get notified about new videos that we make. For example, Colin and Janice Gardiner tell the story of Hazel Tree House in a recent addition to the channel. Find out what they have learned from taking on a new build project. We’ve got a video (or you can read their blog post). And here’s the link to subscribe to our YouTube channel. Enjoy!

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  • HPH381: What is Passivhaus Premium? – with Phil Neve

    HPH381: What is Passivhaus Premium? – with Phil Neve

    Phil Neve explains what Passivhaus Premium is and why he chose to target the standard for his own self build in Somerset. He also talks through his biggest project challenge, which was obtaining planning permission to build in open countryside.

    Interview with Phil Neve

    Phil Neve started his working life as a scientist and oceanographer. He always had a deep interest in alternative energy, and so eventually retrained as an energy consultant and Passivhaus Designer. He then spent 15 years working exclusively on low energy and Passivhaus buildings. Now retired, he is five years into his own Passivhaus Premium project, which has finally got planning permission under Paragraph 84 of the National Planning Policy Framework.

    In the last podcast we talked about Passivhaus Plus with architect Heather Johnson. In this episode we’re looking at the Passivhaus Premium certification and how it differs from the other Passivhaus classifications. We’ll also explore some of the challenges that meant this project was on the drawing board for five years!

    Renewable energy generation on a Passivhaus Premium project will produce a surplus

    While Passivhaus Classic focuses just on the energy consumption of the building, Passivhaus Plus and Passivhaus Premium bring renewable energy generation into the certification process.

    In addition to all the criteria for a Passivhaus Classic, a Passivhaus Plus project must generate as much energy as it uses over the course of a year.

    Passivhaus Premium takes this even further, so that a surplus of energy is produced. Phil explains that this is calculated according to the floor area and the potential of the piece of land.

    Typically a Passivhaus Premium project might produce two to four times the energy it uses. Whereas a Passivhaus Plus project will import energy from the grid in the winter, a Passivhaus Premium will rarely import energy. So the goal of this is to export a significant amount of energy to the grid. This also starts to affect the operational carbon calculations for the building, because you are producing zero carbon or very low carbon energy on top of what you need.

    A Passivhaus Premium project will require permission to export to the grid

    If you’re looking to export above five kilowatts to the grid, which will be a certainty on a Passivhaus Premium project, you will need approval from the District Network Operator. Another must is that you have a three-phase electricity supply.

    Solar PV is often the most practical choice of renewable

    Although any renewable can be used for a Passivhaus Premium project, as with Passivhaus Plus, generation tends to be with solar PV because it can be integrated seamlessly with the building and is generally much more accepted technology than wind turbines, etc. However, if the site has a natural resource to harness, for example being next to a watercourse, then obviously other methods of generation may be preferable.

    Phil’s horticulture project

    Getting consent to build in open countryside can be expensive and time-consuming

    Phil’s self build journey began with a piece of land he owned for a horticultural project. He had absolutely no intention of building a house, but over time things changed. Unfortunately he knew that there was probably only one way to get planning permission to build on a site like this and that was to use the Paragraph 84 exception clause (previously referred to as Paragraph 80, Paragraph 55, etc.) of the National Planning Policy Framework. This allows exceptional one-off houses to be built, where quality is essential and the proposed dwelling significantly enhances the rural setting. However, it’s a lot of work, comes with numerous costs and is all at the self-builder’s risk until consent is granted.

    A satellite view of Phil’s site

    A Paragraph 84 permission often requires consultants

    Whilst Phil felt he had an advantage with his background in construction and environmentally sound building, he was fully aware that he would still require a lot of help. He tells us that he has ended up employing around 10 consultants, sometimes two per topic, covering; architecture, planning, landscape design, ecology, highways and highway safety, and lighting! On top of that there was a design review process using an independent design panel, which was long-winded, complex and expensive. Phil knew all this was coming but it still came in at twice the budget he’d expected.

    A Paragraph 84 consent requires deep pockets

    One of Phil’s initial aims was to prove that exceptional house design under Paragraph 84 needn’t just be for mansions. Exceptional projects can be small scale and not break the bank. He admits he may have been a little naive about this but still believes he can bring the project in at a reasonable cost as a “sweat equity” self-builder.

    Phil has an unshakable belief that we can create great buildings that are efficient, comfortable and healthy. We have the skills, knowledge and materials to do it, but we’re not doing it at volume. He feels that what most people are offered when buying a new house is rubbish and it needn’t be. So, he wanted to show that it could be done better and still be affordable.

    ‘Exceptional’ in this case is pushing the boundaries of what can be achieved

    Phil wanted great performance from the building and to maximise energy generation, and so he targeted Passivhaus Premium. It also had to look good, be beautiful to at least some people, and be very low carbon, pushing the carbon budget down as far as possible. Beyond the house he wanted to improve the biodiversity and ecology of the whole site.

    The size and design evolved over time

    When Phil started the design process he was living on his own and looking at a two-bedroom house around about 120-140 square metres. As he now has a partner, the design has evolved into a more standard 3-4 bedroom family house of around 230 square metres.

    In terms of Passivhaus design, he spent a lot time considering the form (or shape) of the building. The form factor can have a big impact on the ease of construction and the cost. A good form factor is two, with a poor form factor above four. Phil’s house comes in at 3. Early modelling of the building showed that it could achieve the Passivhaus standard, and that Passivhaus Premium was within reach with a PV array on the roof of the building. The overheating risk of the final design is zero.

    “These ideas evolved into the concept of a wedge-shaped house with a single pitch roof facing south.  A very simple design which works very well.”

    A Passivhaus doesn’t have to be a boring box

    Phil explains that to achieve an interesting shape for a Passivhaus there is some compromise on efficiency. However his design will create a fantastic south-facing roof for around 22 solar PV collectors, which will allow them to achieve the renewable generation targets. Internally there will be some sloping ceilings and slightly odd shapes, although Phil believes this adds to the aesthetic.

    Minimising the overheating risk has been a priority

    During the design process there is a balance to be achieved with solar gains. While these are beneficial to keep the house warm in the winter they need to be controlled to prevent overheating in the summer. For Phil’s project there are large windows on the ground floor of the south elevation, but these will be shaded from the summer sun with a 1-metre overhang. For the east facing bedroom windows, in addition to overhangs there will be some vertical shading. Phil also intends to grow plants up that side of the building to help shade those rooms. The building then becomes a place to grow things like hops and vines, producing food as well as providing shade.

    Finding a collaborative architect was important to Phil

    Phil chose friend and architect Mark Ellerby to work with him on the design as he wanted someone independent with good design ideas, who would also be receptive to his input. He says they’ve worked through challenges and ultimately produced a design that works and has satisfied the design review panel.

    The Design Review Panel want to understand how you’ve arrived at the designs

    When a panel of experts are reviewing your design it can feel subjective, because they decide if it is outstanding architecture and suitable for Paragraph 84 permission. So Phil explains that you have to show how you got to the final design – show your workings – and justify the decisions you’ve made.

    Improving the ecology of the site has been a huge focus

    How to improve the land for biodiversity has been a top consideration for Phil, so he asked his ecologist to show him everything he could do to increase biodiversity. He was also aware that they needed to convince people that they would actually put this into practice.

    There are rules and regulations to meet as well as the requirement for biodiversity net gain calculations, which seem to conflict with what is needed for the bat populations. He has had to show that the bats won’t be disturbed by light coming from the house through light spill surveys including a 3D model of the house. This has been agreed by the county ecologist and is now with English Nature for their approval.

    “To anybody embarking on a Paragraph 84 house, you have to look at everything in detail early, predict the problems and be ready to go out and spend the money to get the answers.”

    For a Passivhaus Premium you must be able to export to the grid

    Phil had originally thought about building off-grid, but to be certifiable as Passivhaus Premium you need to be able to export energy to the grid, otherwise you are potentially wasting the excess energy you produce. He now thinks you should only be off-grid for energy and water if you absolutely have to be. All the energy you export is contributing to a low carbon energy supply, and you can access energy yourself if needed.

    Even before construction begins, Phil got a three-phase supply installed at a cost of £2000, and he will then have to run another 100 metres of cabling to the house.

    PHPP calculates the primary energy target for the renewables

    In addition to all the modelling that takes place in the Passive House Planning Package (PHPP) for a Passivhaus Classic project, for Passivhaus Premium there is an extra PHPP calculation for primary energy, which helps work out the renewable energy target. It calculates it in two different ways, so there’s some flexibility as to how much you need for different buildings. Phil’s target is 22 kilowatts. Just to illustrate how significant this is, the average maximum installation in the UK (without planning permission) would be about four kilowatts!

    So there will be 100 square metres of solar PV, which will also be the roof covering. Phil will be using a small ground source heat pump in addition to the PV to provide all the heat and hot water they need. He may add batteries eventually, which with the right switching gear would provide a buffer against power loss from the grid.

    A tried-and-tested build system will make life easy

    Phil is very familiar with the PH15 system, having been part of the Passivhaus Homes team for over a decade.

    Rather than reinventing the wheel with every new design, PH15 makes it easy to achieve Passivhaus performance. It is essentially as simple as you can make a timber structure. Structural I-beams provide the physical strength and form to the building, with a layer on the outside, which is insulation and a layer on the inside which is closing the cavity. This is the racking board, the airtightness and vapour permeability layer. This creates a box, which can then be filled with processed wood insulation. 85% of the structure is insulation, it’s structurally sound, made of natural materials and is airtight.

    During the first couple of weeks of a build, all you’re doing is screwing things together. Phil describes it to clients as an Ikea flat pack house; it just comes on a truck instead of in a box! For Phil the other good thing about the PH15 system is that the internal floors are essentially hung on the inside from ledger beams. The roof is the same structure as the walls, essentially a portal frame structure, with the airtightness layer continuous on the inside of the building.

    Reducing the embodied carbon of the building was part of the design process

    Phil explains that for a typical dwelling there may be 40-50 tonnes of carbon within the concrete used in the groundworks and foundations, with another seven tonnes in the superstructure of a masonry house. Phil was keen to eliminate the use of concrete on his project.

    One option was to use ground anchors, which are like metal screws that hold the building to the ground. The building then sits on holding plates, raised above ground with a ventilated cavity. This creates a suspended timber floor instead of a concrete slab. The approach is proving expensive and complex in terms of buildability.

    A lot of people are now using a modification of a standard strip foundation, where you dig a trench, fill it with some concrete then build cavity blockwork, to allow you to pour a slab over insulation. Phil is looking at a compromise between the two, either by using low carbon cement or other materials instead of cement. Chem-free blocks and low carbon pozzolanic materials would reduce the carbon content of the concrete.

    Another option combines limecrete with foam glass insulation instead of plastics. One challenge is that with these products the costs go up and the performance comes down a bit.

    Building on a slope can mean a lot of excavation

    Phil is building on a slight slope and made the decision early on to excavate soil to create a flat site for the house. This was to drop the house into the landscape for shelter as well as the visual aesthetics. Phil says he might make a different decision if he was looking at it today as it means moving a lot of earth around, although the soil will be used on site as part of the landscaping work and to help retain water on site.

    The land sits between a wooded ridge above to the north and lower lying agricultural lands below to the south. The soil is fairly free draining and he’s aiming to reconfigure the landscape with a series of swales and two ponds to gather water before it penetrates down the site.

    Prices have shot up across the board since Covid

    Phil started the project with a working budget for the building of between £1800 – £2,000 per square metre, but prices have gone up massively since COVID. He’s now looking at over £2,500 per square metre and needs to keep it below the £3,000 mark. He is also planning to do some of the work himself to reduce the costs. Phil will be project managing the build with a small team, commissioning items from local people where possible, and avoiding bigger contractors who sub-contract things out and are therefore more expensive. He admits it’s still an unknown, until he’s got detailed costings and is actually building. He’s keeping the landscaping as a separate budget and one or two of the higher cost items, such as the 100 metre electric mains supply, that other people might not encounter. He aims to have transparent costings that can help inform others.

    A slightly longer build programme aims to take the pressure off

    Phil is setting the build programme to around 18 months, rather than a year, so that there is not too much pressure on everyone. He’s in good health, has always been active, and thinks if you have the right project that’s moving forward the time will fly by. He’s also aware that building projects often go through a hiatus somewhere in the middle, when you wonder why the hell you started and whether you’ll ever get to the end. He’s seen that in other projects, so is prepared for it and knows you just have to get on with it.

    Planning has been the biggest challenge

    Phil has a lot of sympathy for planning departments and can see that they are massively under-resourced but the result is that the system doesn’t work, especially for individuals. The big developers can throw money at it, take everything to appeal and essentially sidestep the planning process on the basis of housing supply need.

    “I’ve always said to my clients, if you’ve got planning and land, you’ve got 60% of the job done.”

    Everything Phil has done so far to get planning approval has been at his own risk. He gives an example, of having to pay an archaeologist to produce a strategy for the build and to be on site whilst holes were being dug. That money would be wasted if he didn’t get planning permission. With approval comes 22 planning conditions, four of which need to be discharged before construction can even begin. If for any reason he couldn’t go ahead with the build after approval, at least he would have a site with planning permission, which would be worth considerably more than before.

    It is all about risk prior to planning approval, so he’s had to be very patient and have deepish pockets to pay for it all!  

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    Passivhaus Homes

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    Exemplar Sustainable Buildings Awards

    The winners of the Exemplar Sustainable Buildings Awards have been announced.

    This was a one-off event to celebrate the 20th anniversary of the Sustainable Development Foundation. It brought together two alliance partners, the Alliance for Sustainable Building Products and the Passivhaus Trust so all of the entrants had to prove performance and demonstrate careful choice of materials and products.

    There were some wonderful projects, and it’s definitely worth taking the time to dig into the details and watch the videos.

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  • HPH380: What is Passivhaus Plus? – with Heather Johnson

    HPH380: What is Passivhaus Plus? – with Heather Johnson

    Heather Johnson from AD Practice explains what Passivhaus Plus is, how it differs from Passivhaus Classic accreditation and what benefits achieving the standard will afford. She also reveals why most of her clients target ‘Plus’ and outlines the steps to achieve this on a project.

    Interview with Heather Johnson

    Heather Johnson has worked in architecture since the age of 16, starting with a summer job as a CAD assistant. She studied architecture for four years at the University of Bath, with placements and work in Suffolk, where she learnt about barn conversions and rural issues. She then did her Part 2 at the Centre for Alternative Technology as her focus shifted to sustainability. A three-month temporary role at AD Practice back in Wheathampstead, where she grew up, turned into seven years and is where she still works today. Heather is now a Passivhaus Designer and has worked on numerous Passivhaus Plus and EnerPHit Plus projects over the years.

    The performance criteria for Passivhaus ‘Classic’ must be met for ‘Plus’ and ‘Premium’ as well

    Most people have heard of the Passivhaus standard, also known as ‘Classic’ but perhaps less well known are the other certifications ‘Plus’ and ‘Premium’. Before looking at the differences between them, these additional classes must meet the same stringent performance criteria laid out in ‘Classic’. For example the airtightness targets, energy demand, overheating risk and so on.

    In this episode we’re going to focus on Passivhaus Plus and find out about Heather’s own project, a barn conversion, which is aiming for the EnerPHit Plus standard.

    Passivhaus Plus sets a target for on-site renewable generation

    Passivhaus Plus brings renewable energy generation into the certification process, setting a target per metre square of treated floor area (renewable energy generation ≥ 60 kWh/m².a).

    It is a step towards self sufficiency and energy security, and a ‘Plus’ project must cover the home energy usage needs over the course of a year. This does not mean it is off-grid, but that the generation exceeds what gets consumed over a year. So there is likely to more generation at certain times of year according to which renewable is being used.

    Solar PV is the most commonly used on Passivhaus Plus projects

    In the UK, more often than not, solar PV will be chosen as the renewable energy source. The main reason is that most houses are in our towns and cities, where space is a premium and roof space is generally available. The technology has also advanced a great deal over the years. It’s cheaper, more effective and can be integrated seemlessly.

    However, any renewable could be used on a Passivhaus Plus project. For example, if you are beside a watercourse then a water turbine might be appropriate.

    Passivhaus Plus encourages a compact building form

    When it comes to solar PV some key considerations are the roof pitch, orientation and surface area of the roof. If renewable energy generation was the starting point for the design of the house, it might lead us to build a bungalow with lots of roof space. However the surface area to volume ratio would not be good, and therefore we may not reach the other Passivhaus targets.

    “The take home point is you still want to make the building as efficient as possible and then add on the generation.”

    The Primary Energy Renewable factors relect the whole picture

    There’s another characteristic the building must meet.

    Primary Energy Renewable (PER) demand* ≤ 45 kWh/m².a

    According to Passipedia: Renewable primary energy (PER) is the unit of energy generated from renewable resources. PER-factors reflect the primary renewable resources needed to cover the final energy demand of a building, including distribution and storage losses. In the case of a PER-factor of 1.5, a surplus of 50% renewable primary energy is needed to be able to meet the final energy demand at the building. The higher the PER-factor, the higher the required resources and therefore the more important the implementation of efficiency measures in order to avoid compensation from non-renewable sources.

    Permission is required to export electricity to the grid

    Although smaller scale renewable schemes (typically under 3.68kW per phase) do not require permission to export to the grid, a Passivhaus Plus project will need approval from the District Network Operator. Depending on the infrastructure of the local area there may be limitations.

    However, Heather says that she has never had a project turned down, but it is always a possibility.

    Additional constraints make achieving EnerPHit Plus more challenging

    Retrofits can also achieve the ‘Plus’ certification. The main difference between a new build and a retrofit is the additional opportunities that building from scratch affords.

    With an existing building the orientation is set and without significant work so is the roof space, orientation and pitch.

    Amongst Heather’s design process she is keen not to break up the long parts of the roof, which are best for energy generation, with rooflights or other roof forms.

    There may be other challenges, as well, such as planning restrictions if a property is in a conservation area. This was the case with Harpenden EnerPHit Plus but a whole roof pitch of solar PV was eventually accepted.

    Heather makes a comparison between the Harpenden EnerPHit Plus which spent £95 on electricity for a year, and her office which typically spends around £200 a month, so it is a huge saving!

    On another retrofit project it made sense to rotate the roof by 90 degrees. This not only increased solar generation but created a mezzanine with a view of the surrounding countryside, which the client didn’t have before.

    Solar PV has come a long way and can now look fantastic

    There can be a double win from maximising generation because a whole roof pitch of solar PV can become the roof finish as well, saving money on tiles, etc.

    Heather often uses the GB-Sol, Infinity system, which is completely seamless.

    On a Passivhaus Plus project in Wheathampstead there is a more conventional in-roof solar array, which does not cover the whole roof. The solar panels are inset so they’re flush with the concrete tiles but it’s not a seamless finish. Interestingly, the clients wished they had put more solar PV on the roof.

    Heather say the cost of solar PV has come down dramatically from when they were first being installed. Unfortunately, the feed-in tariffs for exporting have also gone down, but there is still a much shorter payback period.

    There are also schemes around, such as Solar Together in Hertfordshire, that give discounts for solar installations. It’s becoming a much more attractive offering, especially with more people opting for electric cars.

    Solar PV does not just have to be on south-facing roofs

    South facing roofs tend to work best for solar PV but that doesn’t mean it ends there. When Heather speaks to the suppliers and specialists, they’re quite keen on southeast and southwest as well. This gives a longer period of time generating power, so can be better for the homeowner and takes pressure off the grid at peak export times. North facing won’t give as much generation, but a mixture of orientations will give more consistent energy generation throughout the day.

    Use as much of the energy generated on site, before exporting

    There’s normally a hierarchy of uses for the energy that is generated on site.

    For example, it may be running a heat pump, topping up the hot water, charging a battery or an electric car. So exporting to the grid would be the last option.

    Different suppliers also pay different rates for exported electricity and these rates will probably vary during the day. So if you have a home battery you can maximise your return by importing and exporting at specific times. For example, if you need to draw from the grid to charge your battery it makes sense to do it overnight when the tariffs are low.

    Heather even wants to make her ‘long, thin barn’ an EnerPHit Plus

    Heather and her husband fell in love with a barn in rural Hertfordshire, which was ripe for modernising. It’s a long thin brick building that is not really conducive to a Passivhaus project, but this has not deterred them!

    The first air test achieved 0.7 air changes per hour at 50 Pascals so it’s well under what’s needed for the EnerPHit standard.

    As they are targeting EnerPHit Plus, the large roof area makes it easy to achieve the required generation and they are looking to install around 50 solar PV panels.

    Heather’s barn is being converted in two phases

    Heather is converting the building in two phases. As it is long and thin (around 25 metres) the barn will have two MVHR units (to limit the length of duct runs). Phase one is the old traditional barn, the taller area, with a side utility room and shower room that’s run off one system. They plan to put up a temporary wall up at the end, so they can live in that part of the house, studio style, whilst they carry on fitting out the rest of the house.

    A new timber structure is being built within the old barn

    Heather is taking a similar approach to this barn conversion as they did at Stirley Farm. They are building a timber box within the old brick structure.

    So there’s an insulated slab (the Isoquick system) and I-stud walls which are filled with cellulose insulation. The new extension will be finished with timber cladding, whilst the existing barn will be the existing brick, retaining the historic fabric.

    The design does not add any loads to the original building as that would have required underpinning. The existing timber trusses have been retained and now function as tie beams within the new timber frame structure. Heather explains that because the building is essentially a long tube, it needs the beams to stop it just squishing and falling flat.

    Dealing with ventilation and moisture across the old and new structures

    Heather outlines that where they’ve built against the brick wall, they have a nominal 50 to 100mm cavity, which is much wider in places because the brick walls are not straight. With the new timber clad structure there is a rain screen system, which is battened and counter battened out before the cladding is put on. The timber frame is also wrapped in a membrane before the cladding goes on, so any moisture would hit the membrane and trickle out the bottom, as with many similar systems.

    The bigger risk with phasing the work is that they don’t ventilate the uninhabited internal spaces correctly. As it is airtight and insulated, they need to make sure air is circulating by using fans and opening windows. Otherwise condensation could occur which would eventually lead to mould.

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    AD Practice

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  • HPH379: What is inclusive design? – with Stephanie Kyle

    HPH379: What is inclusive design? – with Stephanie Kyle

    Stephanie Kyle from Floyd Slaski Architects explains how we can design for disability, gender, religion, and anything that’s considered a protected characteristic under the Equality Act. She also highlights the biggest challenge of inclusive design which is people’s differing needs, and suggests how we best go about designing spaces.

    Interview with Stephanie Kyle

    Stephanie Kyle is a Senior Architect and Inclusive Design Consultant at Floyd Slaski Architects, who specialises in design for neurodiversity.

    Stephanie was diagnosed with Auditory Processing Disorder (APD) when she was a child, but it wasn’t until her 20s that she found out she was autistic. APD is a neurodivergent condition and because this was identified early she didn’t have to grow up masking her behaviour to fit in, and got the support she needed at college and university.

    Her inspiration for entering the world of architecture came early on during a workshop at her school. An architect wanted to hear their ideas about an aquarium that was being proposed in the town. When it was built, she went on a school trip to see it, thought it was atrocious and that she could do a better job herself!

    Throughout her education and architecture training she was drawn to inclusive design, which includes designing for disability, gender and religion, everything that’s considered a protected characteristic under the Equality Act. She now specialises in neurodiverse, inclusive design and nonvisible disabilities; focusing on how we can design better for dementia, autism, ADHD and all the nonvisible conditions, like epilepsy or chronic pain conditions.

    All architects and designers have a duty of care to the end users

    Under the ARB Code of Conduct all architects and designers have a duty of care to the end users, no matter what their religion, gender or disability. Knowing the needs of the people who will use a building is the most important thing. It’s an opportunity to address varying needs and tailor the space in better way.

    There are three neurocognitive profiles that each have differing sensory processing

    The three neurocognitive profiles are neurotypical, neurodivergent and neurodegenerative. All these profiles describe the way that the brain is set up, its instruction manual.

    The majority of people are neurotypical, but neurodivergent and neurodegenerative brains receive, process and label information in a different way.

    Our senses help us navigate our environments

    In addition to sight, hearing, smell, taste and touch, we have three extra senses that help us relate to the built environment.

    Proprioception – this is our sense of hand eye coordination, essentially where our body is in relation to itself.

    Vestibular sense – this is where our body is in relation to the space around us, so being able to sense movement, maybe in a lift moving up or down, or in a car speeding up or slowing down. It’s also the sense that causes car sickness.

    Interoception – this is the sense of what’s going on internally in our own body. So being able to sense if you’re tired, if you’re hungry, if you need to go to the toilet.

    We have probably experienced a temporary sensory processing difference

    If we are drunk, we perceive our environment differently. The speed at which we process is different, the way we speak, how we move, and think is different. Another example is a migraine. Lights may be really bright and sounds really loud, which is our brains processing that sensory information differently.

    Stephanie explains that some people with sensory processing differences may experience those things all the time, but it will vary from person to person. If somebody is autistic, they might be hypersensitive to sound, which is why something as simple as a hand dryer going off might cause distress. Visual processing is often different; colours might be perceived as significantly more intense or any high contrast patterns might look like they’re moving so for some people it might look like an optical illusion all the time.

    There is no such thing as one design solution fits all

    Stephanie says we have a stereotype of autism based on films that show a nine-year-old boy rocking in the corner, who screams if you touch him. Although there will be some people that match that description, autism presents itself differently in each person, with individual sensory needs. This makes designing spaces for the public difficult as it becomes impossible to cater for everyone’s individual needs, so instead we design for the majority of neurodivergent people.

    Fixed elements should be muted, natural and calming

    By using lower chroma colour palettes we can create lower sensory environments for the primary surfaces. Things that you can’t change easily, like walls and floors, should be as muted and as natural and as calming as possible. You can then add in boldness, in removable features, things that can be changed easily, like a multi-coloured zigzag rug. You can still have feature colours and design elements if you keep them at a lower chroma intensity.

    Needs can even change during the day

    Stephanie points out that an individual’s needs may also change during the day, with more energising spaces perhaps needed in the morning and then a more calming space in the evening.

    Two people sharing one space may have conflicting needs

    When designing spaces another consideration is hypersensitivity and hyposensitivity. For some people an environment can be over-stimulating, whilst for others they may require more stimulation.

    “As an autistic person, I need complete silence to work, but my brother has ADHD and he is the exact opposite. He can’t concentrate if a room is silent, so if he goes to a cafe where there’s background noise.”

    Similarly, some people may require absolute silence to sleep, whereas others need to play music or have some background noise to help them sleep.

    We can design for most senses

    After our visual sense, smell – or our olfactory sense – is the most powerful in terms of way-finding and navigation. It is possible to design for this sense too. For example by planting scented flowers at different ends of a building, the prevailing winds will carry those scents through.

    It is much harder to design for taste. Some autistic children or people with dementia may want to explore their sensory environment by putting things in their mouths. By using low VOC paints and non-chemical materials we can make sure they come to no harm. Similarly with landscape planting, avoid anything that is toxic to humans or animals.

    Your home is one space that can be designed to your individual needs

    The one space you can control is your home environment. Stephanie shares her preferences, although she stresses that someone else with autism might want something completely different.

    When working she cannot stand any noise whatsoever, so her office is soundproofed. She controls the light levels and glare from intense light with light filtration blinds as well as blackout blinds. She has colour-changing lights and individual thermostats in each room to control the temperature depending on her needs.

    All the colours she uses are low chroma, with a lower intensity than ‘brilliant white’. Each of her rooms has a different approach depending on the type of energy she needs for that space. When she’s cooking, she needs high energy so having a more energised space helps her.

    Sometimes simple measures can improve soundproofing

    Stephanie’s own house was built in the 1960s and needed updating. She started by insulating the ground floor, using mineral wool in the sub-floor. Her office has a separate acoustic lining that she put in using acoustic insulation boards.

    There are, however, a few simple solutions that can transform the acoustics of a room. Stephanie suggests changing the floor finishes and putting up acoustic noticeboards. Rubber underlay, for example, is more soundproof than other types of underlay. Check out the noise reduction rating of each product. Typically, anything that reduces the sound by 14 decibels or more is going to be a significant improvement. You can also add acoustic absorption through soft furnishings and floor-to-ceiling thick curtains with linings. If you want to go further you can add another wall lining to the existing wall with a small stud frame that you fill with acoustic insulation.

    Consulting people with ‘lived experience’ is really useful

    It’s important to understand how many different conditions exist and that it’s impossible to know them all. Therefore in Stephanie’s role as a Inclusive Designer, whenever she meets somebody with a disability that she’s not encountered before, she asks them about what would make the environment better for them.

    Asking the right questions is important

    Meeting people with lived experience of having a specific disability or characteristic is always the best way of learning. Find out about their day-to-day needs, what they find challenging, what they would like to be improved, and so on. Then it is up to the architect to work out how to design the space to suit that client.

    Building regulations don’t go into much detail to allow things to get built

    Stephanie says that the building regulations are broad and general, because if they were too onerous, it would be difficult to get things built. The main criterion is that all people should be able to use all parts of a building. Everyone should be able to access it and operate everything within it in the same way. That means disabled entrances shouldn’t be put round the back of the building or windows have controls that require two hands to operate them. Touch screens and app-controlled devices for lighting controls are all beneficial.

    Part M of the Building Regulations provides a guide on how to achieve this accessibility but it’s limited. Guidance BS 8300 is significantly better as it provides more detail, including the difficulties people have with certain things. For example, rather than it just telling you put an oven at 900 to 1000 mm off the floor, it tells you why you need to do that.

    PAS 6463 is a guidance document specifically about neurodiversity and designing for neurocognitive and sensory processing differences. It provides a lot of detail on the issues for people but doesn’t tell you how to fix them. It’s then left to the designer to come up with a solution.

    Social media can help you connect to people with lived experience

    Stephanie’s top tip is to speak to people with lived experience, because that will be so much more enriching and insightful than consulting guidance documents. Social media is a great tool to help connect with people who have specific conditions and are willing to share their experience. Search using different hash tags.

    We could all do better in our approach and the language we use around this topic

    Disabilities can be dynamic so on some days a person might need a walking aid, or a wheelchair and then on a different day, they might not be using anything. It doesn’t mean they were faking their condition on the other days. This also applies to neurodiversity, where people can have really good days and really bad days.

    Stephanie says that ‘disability’ and ‘disabled’ are not bad words, and we don’t need to avoid saying them. We need to acknowledge that disabled people exist, that they are living in a world that is not designed for them. Typically, disabled people are disabled by the environment, because if the world and all the buildings were set up to be inclusive for everybody, there wouldn’t be as many problems with using the built environment.

    Finally Stephanie asks people not to say ‘people are suffering with an illness or condition’. Stephanie definitely doesn’t feel she is suffering; she’s having a great time!

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    Floyd Slaski Architects

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  • HPH378: Accessibility for all – with Guy Harris

    HPH378: Accessibility for all – with Guy Harris

    Guy Harris from AccessiblePRS explains why accessible housing is important, what the key considerations are and how to deliver it well. He also shares his experience of designing his own house as a wheelchair user.

    Interview with Guy Harris

    Guy Harris is the Director of AccessiblePRS, which he founded in 2020 to increase the supply of wheelchair accessible rental homes. He became a wheelchair user in 2003 after an accident and now works to promote good accessible design for all buildings.

    Accessibility is the ability to move around a home at all stages of life

    Quite often the terms accessibility and adaptability are used interchangeably, and people will even have their own understanding of what they mean. So Guy defines accessibility as the flow and space of a home, and the ability to move around it at all stages of life. This can be as parents with young kids, older people, wheelchair users, people who have dementia, and so on. Accessibility is understanding how we relate to our spaces and making them human centred.

    Accessible spaces can benefit everyone

    Guy believes that making accessibility about the person with a disability is fundamentally flawed, because it means we bring all our negative stereotypes and misconceptions to that approach. Instead of being a burden this can be playful, glorious or liberating for a whole range of people.

    “When I tell stories about where accessibility is in place, very often, I tell them about people who have no disability at all, and show them the advantages, so that we can understand that this really is not for some people, this is for all people.”

    Wheelchair users face constant frustrations from existing properties

    In 2003 Guy made a mistake when crossing the road and was struck by a lorry. From that point he became a wheelchair user.

    Like his, most disabilities are acquired and this made him realise that he had been part of the problem before his injury. He worked on property projects, and it was only after the accident that he understood the constant frustrations for wheelchair users around property, which also gave him an insight to the opportunities.

    Funnily enough, before his accident, Guy had bought a 1000 square feet shell apartment in London, which he made into an aspirational and indulgent space. It was only afterwards that he realised he’d actually designed a wheelchair accessible space. However, he admits he wasn’t in the wheelchair accessible mindset at the time. The Disability Discrimination Act had just come in, which meant that sockets and switches had to be at a specific height. He remembers clearly saying, “I don’t have a disability, I don’t want them at this height, I’m not doing it.” He sees a nice juxtaposition there, both wilfully not wanting to do anything around disability, whilst on the other hand designing the perfect space for it.

    Building for accessibility requires a mindset shift

    While we have made significant advances in gender equality, eliminating racial discrimination, and LGBTQ+ rights, Guys says that disability feels like the poor cousin.

    Until we get over our subconscious fear around what it means, what it looks like, and not wanting to believe that it can ever happen to us, we’re always going to have an issue with the idea of building accessibly.

    Guy feels we either need to change our relationship with disability, or perhaps with the language around accessibility. Accessibility is simply good design.

    No one will come into this home and go, “Wow look at that accessibility.” It really features disability in a wonderful way. You come in and you go, “Hey, wow, look at this home.”

    Key requirements for wheelchair users are more space, a level home, step-free access and a purpose designed bathroom

    As a wheelchair user Guy needs things to be designed in a certain way to be able to live autonomously and independently. He needs a bit of space, wider doors and consideration of how they’re positioned relative to things that come next to them, whether it’s cupboards or walls. Step-free access is also important, which might include lifts or ramps. Bathrooms are a critical room, often a wet room, and a hoist may be needed.

    By designing for a wheelchair user, you design for any eventuality in life.

    You don’t need a specialist architect for a house build

    Guy’s architect wasn’t a specialist in disability or accessibility but was amazing. He drew the brief out of them carefully, in the same way that he would for any other client, considering how they lived and wanted to live.

    One aspect that really helped Guy was a study trip, visiting existing properties and trying to absorb useful information.

    “People make decisions without actually seeing what they’re making decisions on, which is nuts, frankly. And so the more we got to see different things and understand the implications and the benefits and the costs, the more we naturally arrived at the decisions we made.”

    There will be opportunities in the design process

    The design process didn’t revolve around the wheelchair, but as they went along, they realised that there were opportunities coming from their discussions. For example, the spine wall down the middle of the property, has quite a few structural posts. These created alcoves and space to put furniture, but also were the perfect place for handholds.

    The house evolved into an ecological build through the design process

    Guy explains that they were starting with a blank sheet and ecological architecture or doing something green, was an obvious question to ask, although at that point he really didn’t know what it meant. He did some investigating but wasn’t getting anywhere until he heard a sustainability consultant talk at a show and he’d never heard anyone speak so much common sense about how to build. She then recommended the architect, who he eventually hired.

    “We arrived at straw, having said the only thing I know I don’t want is straw!”

    After two separate non tangible experiences they decided to build with straw. The first happened in Scotland when they visited a straw bale building. It was blowing a hoolie outside and because Guy is paralysed, he doesn’t feel his legs, but his legs started to tingle in a warm, cosy, enjoyable way. They then went to the property next door, which was a different build and a nice layout, but it just felt cold, without the same richness.

    This prompted them to visit another straw build, Haringey Community Centre in London. At the time Guy’s wife was pregnant and wasn’t really enjoying the pregnancy, nausea, low blood pressure, always moving from side to side. But inside the centre he noticed she was standing still and looked comfortable. As soon as they went back outside the nausea started again, but when they came back inside it stopped. There was no way of understanding what it was, but on two separate occasions they had both experienced this magical feeling, and so it became a no-brainer to build with straw.  

    Accessible homes don’t have to be ‘Grand Designs’ projects

    Guy is aware that his bespoke home might be considered a grand design style building, but accessibility can be achieved at most scales.

    Aspects Guy particularly enjoys is the volume of the internal space and how light is brought into the property from all directions. There’s a strong connection to the wooded area outside.

    Their choice bio-based materials has delivered on many levels

    Guy’s home is a load-bearing straw bale house, with bales almost being used like bricks. On the inside natural clay plaster is applied directly to the straw, whilst the outside is lime render.

    The house has an organic, natural feel whilst still being mainly straight lines with a few nice curves and subtle colours. For Guy the house feels grounded and is peaceful and calm inside. The design is largely open plan, which allows them to be doing things together in the same space, but also when doing things separately they somehow still feel connected.

    “I think one of the subtle things about the house is how when you’re in it, everything feels right.“

    Look at the value of what you build rather than the cost

    Guy wishes there was more consideration around value rather than looking purely at cost. Building the cheapest possible home is unlikely to deliver a good outcome. As someone who works in property, Guy understands that the budget could be spent in a million different ways. For example, they could have had more space for the money or built more quickly, or spent less, but that was not the priority.

    The materials they were using and how they were building was important, and he was taking a long-term view. Guy intends to stay in this house for the rest of his life, so the initial cost will balance out over that time. This is a quality-of-life investment.

    An accessible entrance

    Make sure you get good advice when building for accessibility

    Building and designing homes is an expensive business and it’s easy to make mistakes around accessibility, so Guy suggests getting external input when required.

    “If you want to design for more possibilities, take advice. If you want to, I don’t know, have specific sound or acoustic attributes or engineering attributes, you pay for advice.”

    He shares a couple of examples of how planning upfront can help you avoid problems further down the line.

    He stresses that it is important to consider how the walls, doors and windows relate to each other. How you create the ratios and the space, your floor surfaces and the furniture that you need. Bathrooms are an expensive room that need designing properly, because retrofitting a standard bathroom to accommodate grab rails or a ceiling track hoist, could mean starting again from scratch.

    Another scenario is with sliding patio doors, which may not open all the way, meaning the opening is then less than a wheelchair width. Or you put a ramp in but have forgotten that you need a level platform on both sides. These are simple things, but they matter and so paying for advice could help prevent costly mistakes.

    “In every design meeting, just ask the questions, what can I do? What if? What does it look like? What does that mean? Have we thought about? Do you know about? And take it from there, because even the simplest of questions will inform the design and make people think.”

    The regulations are helpful but provide minimum standards

    Guy says that, for the most part, the regulations are extremely helpful. However they are open to interpretation and deal with minimum standards. If you have a designer who doesn’t understand the intention behind the regulations, they can interpret them, sometimes in bizarre ways which mean the regulations have been met but are meaningless. And for Guy when we aim for minimum standards, we nearly always fail. Good design is about understanding what is actually needed and designing for that. If you go for best practice, then the regulations are almost guidelines. Experience and advice will steer you much further.

    There is a National Register of Accessibility Consultants, NRAC, and those are people who have experience of designing for accessibility. A consultant can come in at the beginning, at the design phase, be part of those conversations and reviews, and support your architect in optimising the design.

    We should be designing for an ageing population

    By 2040 there’ll be more people in the UK aged 65 or over than there will be of working age, which for Guy, begs two questions. One, where are they going to live? And two, who’s going to look after them? The only feasible answer at the moment is an end-of-life residential care setting, which he thinks is going to be quite grisly for a lot of people.

    It’s already common to find that newly injured people with disabilities get stuck in hospital, because there’s no accessible accommodation available.

    So if you have the opportunity to create your own home, it’s a good idea to consider future needs. Otherwise you may face a situation, an illness or a disability, and you won’t be able to cope and you’ll be forced to move out.

    Communities should be able to house us all

    Guy feels that in the UK we put accessibility in a silo like all the other housing issues, such as affordable homes and green homes, whereas accessibility could cut across all the silos. He suggests every design meeting should ask questions around accessibility to inform the design and make people think.

    He gives an example where his architect was working on a community project in Scotland, designing holiday lets in a woodland setting. Initially they were not thinking about accessibility, but when they embraced it several things happened.

    The first thing they realised was that by designing the bathroom for accessibility it helped with the modular design and made things flow. The second thing was by making the route from the car park to the homes suitable for wheelchairs they could get a small telehandler to the construction area. This saved time and money when moving materials and the process went more smoothly. The third thing was the community realised that if any of them had an accident or got injured and needed accessible accommodation they would now be able to stay in the community rather than having to move out.

    For Guy this is an important point to highlight. Traditionally we’ve always included everyone in a community. We really need to get back to that understanding of what community means.

    “One of the things I love to do is show beautiful, accessible design, because I think that’s where people suddenly start to get it and realise that it’s not clinical, institutional, ugly, it’s actually something that nourishes and enhances our lives.”

    Find out more

    AccessiblePRS

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  • HPH377: Retrofitting a 1950s semi-detached ex-council house – with Toby Cambray

    HPH377: Retrofitting a 1950s semi-detached ex-council house – with Toby Cambray

    Toby Cambray talks about the experience of working on his own retrofit project, and the lessons learnt in the process.

    Interview with Toby Cambray

    Toby Cambray co-founded Greengauge building & engineering consultancy in 2010, specialising in sustainable and low energy design. He is a certified Passivhaus Consultant and has completed a PhD on moisture in buildings.

    In the previous episode we discussed moisture risk in buildings and how to assess it.

    There’s no such thing as an ‘easy’ retrofit

    There are always compromises, so how do you best juggle and manage those? Toby bought his house with the idea that it would be relatively straightforward to retrofit. There was nothing (e.g., listed building status) to prevent getting permission to make changes.

    The house had deep eaves, making external insulation easier. It was a question of how to execute that while minimising thermal bridging, getting the windows in the insulation zone, and incorporating airtightness.

    The original bay was a feature Toby decided to remove

    Toby had lots of ideas of what he would like to do. He built an extension and did some minor remodelling first, before starting retrofit work. From a holistic point of view, it would have made sense if the extension had been planned to receive the same external insulation that was added to the house later. The building would have performed better too, as there is a thermal bridge where the extension’s cavity wall meets the new external wall insulation on the main property.

    Living in the home first can provide useful information

    It takes time living in a home to understand what’s best for how you use it.

    There is also thinking about how the home might need to be used in future, and other considerations like whether you’re adding value.

    The floor plan of Toby’s house already worked well, so there was little reason to change the layout. He considered taking out a wall with a chimney. That would have been a major structural challenge, so he prioritised keeping things simple and less expensive.

    Watch an entire retrofit of this mid terrace home in The Hub.

    A truss and fill insulation system can take different forms

    There’s a lot of experience with truss and fill systems, especially within the AECB membership. A timber frame is fixed to the outside of the building, with a thin wood fibre board over it to create a cavity. Any blown insulation can then be installed to the cavity; Toby chose cellulose insulation.

    There are different ways of doing the frame too. Toby used a Larsen truss with 50 x 50mm battens on the wall, then plywood gussets to support an outboard batten. You could equally do it with an engineered joist, or similar.

    There are different ways of finishing the outside. Toby used a 25mm batten cavity with a render-carrying board, and then a render finish. It could also be timber clad. Rendering straight onto the wood fibre is possible but might need more careful thought when it comes to rain robustness.

    A second layer of defence between the outside surface and the insulation is comforting, even if you’re not in a very exposed area for rain. If you have render direct on insulation and the render cracks, there’s a higher likelihood of water passing through to the inside.

    Plywood window boxes were constructed to take the new windows

    The first step was preparing the window openings

    To ensure the new windows were in line with the cellulose insulation, Toby built plywood boxes and installed them in the opening so they cantilevered out. They were fixed through the face of the ply into the edge of the cavity wall masonry, and they allowed the new windows to project into the insulation zone.

    The bay was removed

    New studs for the insulation layer

    The cement board going on

    A cavity acts as a capillary break in the wall build-up

    The cavity in the original wall build-up acted as the capillary break to stop moisture reaching the inside of the building. With the retrofitted wall build-up, Toby made sure the 25mm batten cavity behind the render-carrying board was ventilated and served that function instead.

    Below-ground insulation links the floor to the external walls

    Toby dug a trench around the building, installed moisture-resistant insulation, then backfilled it and used paving slabs to hold the insulation in place. The 200mm timber frame with the cellulose sits on top of that. The below-ground insulation finishes just above ground level to keep the timber clear of ground level. It required a lot of hand-digging and re-doing drains that are close to the house.

    Planning ahead helped with airtightness in the roof

    Toby removed the old insulation from the roof. Some leftover mineral wool from the extension went between the ceiling joists, followed by a vapour control membrane over the joists. He installed cellulose insulation over the membrane – it comes in compressed bales which you open and it expands into loose cellulose.

    When installing the membrane, Toby left plenty of length on it and folded it back under the rafters. When the scaffolding was up and the end of the rafters exposed, he peeled and then slit the membrane so it could fold down between the rafters. It was then a case of taping that all around, first to the rafters and then down onto the existing render. It felt like it was going to be time consuming, but then proved to be okay once Toby got into it.

    To achieve continuity of the roof insulation with the wall insulation, Toby was able to remove just a single row of tiles. He slipped in some insulation that the wall insulation could butt up to. Waterproofing it required some leadwork, which was an unexpected expense, but a nice way to finish it and robust so it won’t let moisture in.

    Following established principles can help keep embodied carbon low

    Toby hasn’t calculated upfront or embodied carbon. Instead, he has followed general principles that he has learnt from other projects, including using very little concrete or steel.

    In terms of concrete, there are small amounts of mortar for repairs and holding the paving slabs in place for the below-ground insulation, plus the 12mm cement board carrying the render. Some stainless steel bars were required as part of a Helifix Helibeam system, which was used to replace a failed concrete lintel.

    Retrofit can make it tricky to accommodate MVHR

    In an ideal world, Toby would have chosen MVHR, but finding a good position for the unit is always difficult in a retrofit. Put it in the loft, and access for maintenance is harder. Put it in a room and you lose valuable utility space. Installing the ducts is also tricky and can involve a lot of compromise.

    Toby chose an Aereco MEV system over MVHR. The system was installed at the time he built his extension, as this was the best time to get ducts running to and from the loft.

    MEV is effectively the extract half of a full MVHR system. There’s one fan in the loft, with a duct to each wet room. Each living space has an inlet through the wall, and on each inlet and outlet is a humidity sensitive material that passively operates like a damper. When someone has a shower, the damper opens a bit more to help clear the elevated humidity. The fan in the middle has a pressure sensor which increases the fan speed when the terminal opens more.

    Decentralised MVHR, with individual room units, could have been an option but Toby’s experience is that it tends to be relatively expensive to do a whole house that way.

    Plan ahead for low carbon heating

    Toby’s home still has a gas boiler, a decision he was comfortable with at the time. He will upgrade to an air source heat pump at some stage, and has the infrastructure and electrical supply in place where the hot water cylinder would probably be positioned.

    The retrofit industry perhaps overlooks the DIY culture of the UK

    Toby has travelled in parts of Europe and recognises the DIY culture we have in this country compared to other places. With motivation, and the right research and guidance (including the House Planning Help podcast!), a proficient DIYer could undertake a retrofit project.

    But it’s also important to be aware that it’s a lot of work, with stress and long hours. Toby was working under floodlights until midnight the day before his cellulose insulation was installed, finishing off taping so there was a cavity ready for the insulation.

    Standard details are a good starting point for DIY retrofitters

    You might have to pay for the information, but it’s less expensive than engaging a consultancy service. If you have building experience and broadly know how a timber frame goes together, or how a masonry wall goes up, then a lot should be fairly obvious. It’s about thinking through the next steps as you work, and coming up with solutions for how X joins to Y.

    Toby understands moisture risk and so designed a window detail himself that others thought was overkill. He was happy with it as a belt and braces approach to keep water away from the cellulose insulation. It’s a case of assessing risks and accepting when there is value in paying for advice. Structural calculations are one area that Toby was glad to have professional support.

    Every project has unique technical challenges

    Toby uses the example of external insulation. There are a host of ways to do it, but you can guarantee that any project will always throw up a detail that no-one has ever come across – or, if they have, that a solution is not well documented. Again, it’s taking time to think about how to do it well using the array of products that are available.

    Budget for and prioritise the ‘big ticket’ items

    The biggest expense on Toby’s project was new triple glazed windows. The next biggest cost was re-roofing the property, as the bituminous underlay needed replacing. The roofer was able to reuse the original tiles, and the roof work was carried out while scaffolding was up already, which helped. The cellulose insulation was a big undertaking, but not necessarily the biggest cost. Toby did a lot of work himself getting the timber frame ready.

    If Toby tried to value the time he has put into the project then it would probably be one of the most expensive retrofits done recently. He has really come to respect the speed at which professional builders work. But he is also interested in the subject, gets enjoyment from doing the work, and can take lessons learnt back to his practice. All of that provides additional motivation.

    Junction details and internal finishes take a lot of time

    A big lesson for Toby was that lots of time, thought and effort goes into the junctions. The timber frame went up in a few days, which really looked like progress. On the other hand, working at the foundations, taping around the rafters, and sorting out the windows all took a long time.

    A lot of functional and structural items don’t have to look nice, they don’t have to be finished. But since Toby has begun to work inside, time has been eaten up finishing window reveals, and sanding and painting so that the finish is to a standard he wants.

    It’s hard to capture in words how much more comfortable a retrofit is

    In conclusion, Toby observes that he knows the physics of why his home feels more comfortable, but he finds it difficult to express how different it feels when everything’s a more even temperature. You can only truly feel it by experiencing a well-insulated house. It’s a feeling that it just … works.

    Find out more

    Greengauge

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  • HPH376: What is WUFI? – with Toby Cambray

    HPH376: What is WUFI? – with Toby Cambray

    Toby Cambray talks about the risks associated with moisture in buildings, and the modelling techniques – like WUFI® – that can be used to assess those risks.

    Interview with Toby Cambray

    Toby Cambray co-founded Greengauge building & engineering consultancy in 2010, specialising in sustainable and low energy design. He is a certified Passivhaus Consultant  and has completed a PhD on moisture in buildings.

    Condensation on windows is a common sight in British homes

    In buildings, moisture is water in any form

    When we use the term ‘moisture’ it can refer to liquid water, water vapour in the air, or even ice. People might be most familiar with water vapour, and how humidity changes with temperature.

    It’s also important to think about materials – especially historic building materials – and how they interact with liquid water. And when you add insulation to buildings, moisture is something that really needs attention paid to it.

    Moisture movement in buildings is about equilibrium

    In the laws of physics, all things try to minimise their energy. For example, if you have an area of high pressure next to an area of low pressure, the molecules try to ‘even themselves out’ and minimise the total net energy. In a different context, that’s what is happening with moisture. In an area of high vapour pressure with lots of water, the water will try to distribute itself as evenly as possible.

    The potential risks from moisture in buildings are varied

    Organisms that cause mould or timber decay can thrive where moisture is present. Moisture also leads to problems like corrosion, especially of steel. In heritage buildings, it can lead or contribute to deterioration in masonry, through processes like freeze/thaw damage, or salt transport and crystallisation.

    Damp and mould inside a historic building

    The two main moisture strategies are moisture open or moisture closed

    Putting it very simply, you can either manage moisture or block moisture. Most modern buildings are moisture closed, or moisture blocking. Features like damp proof courses and vapour control layers aim to stop moisture getting to where we don’t want it.

    In traditional buildings, when these modern products obviously weren’t available, builders worked with materials in a way that managed moisture – often by absorbing it and holding it, before allowing it to dissipate safely. Porous materials like stone and brick can generally store and transport both liquid water and moisture vapour.

    There is still a lot to be understood about moisture in buildings

    Toby has been carrying out moisture modelling work for over a decade. Any simulation has shortcomings, so he sees it as the responsibility of practitioners to understand as much as possible about the physics of moisture so they can then understand when models are most useful. Toby acknowledges that he still has lots to learn about the physical processes that calculation models are trying to simulate.

    Dew points are not the best way to assess condensation within building structures

    While we want to avoid condensation within the structures of our buildings, dew points are not always a great way to understand potential moisture risks. This is especially true in masonry materials and traditional constructions. A dew point is the temperature at which condensation occurs for air of a given humidity.

    Simpler calculation methods that rely on dew points, like the Glaser method, don’t reflect the full range of real-world conditions. They don’t take account of rain on the outside of the building, or moisture transport and storage in liquid form. Their limited scope might be okay for some situations, but they are not sufficient for making sensible judgements about many structures, including historic buildings.

    For example, you could have a structure that never suffers from condensation, but still gets a serious problem like mould. The calculation method might tell you about the condensation risk, but it isn’t sophisticated enough to calculate that humidity is high enough for mould to form.

    WUFI software is a more complete way to simulate moisture movement

    It’s not perfect, but it is a more complete approach to modelling moisture movement in buildings and modelling how water moves around within porous materials.

    In the software, the user builds up the element to be modelled. They then select a climate file with data about sun, wind, temperature, humidity and rain. Then the internal conditions are inputted, some other parameters are set, and the simulation can be run. And the simulation predicts the temperature and moisture content at any point within the element’s structure. Using the temperature and humidity profiles that it outputs, together with some post-processing tools, it’s possible to assess whether problems like mould could occur.

    Temperature and relative humidity data over time

    There are still uncertainties in WUFI calculations

    As with any software or calculation, nonsense in leads to nonsense out. The WUFI software has a database of several hundred materials. Some are modern products with known performance.

    It also includes porous materials. Because these materials have unique combinations of liquid transport properties and vapour permeability, there can be enormous variation even within a single category of materials. For an existing building, some assessment and measurement of the material is needed to then make an informed selection from the database.

    Other uncertainties include internal conditions. For example, you might not know if you should be accounting for a densely occupied house with poor ventilation. Toby explains that the advantage of modelling is that you can play around with some of these variations and explore the different issues to understand their effect.

    An example of how moisture moves within a wall build-up that has wood fibre insulation

    The simulation is quick to run, but interpreting the output is key

    Toby says his team likes to spend a couple of days on a project, normally. This gives time to go to site, collect material specimens and analyse them. Once the data is available to enter into the software, the actual simulation can take anything from five minutes to a few hours to run, depending on complexity.

    The real value is in the interpretation of the results, and providing a professional opinion and risk assessment. In complex situations, things are much more nuanced than a simple pass or fail. It can often mean going back to a design and altering it to reduce risk further. Toby’s work really comes into its own in more unusual situations with higher risk constructions, perhaps featuring an unusual combination of materials.

    There are lots of good sources for help and advice

    For simpler enquiries, Toby and the team at Greengauge will often direct people to a variety of reputable suppliers who they have built relationships with over time. Examples include Ecological Building Systems, Back to Earth, Natural Building Technologies (now part of SOPREMA), and Best of Lime.

    For WUFI calculations, there are no specific qualifications to look for when engaging someone. There are a small number of training courses, but a lot of it comes down to experience: reading academic papers for background, and looking at buildings on site to understand the difference between simulation and reality.

    The most common use of WUFI is with internal insulation

    A sophisticated modelling tool like WUFI is most suited to applications that have a lot of variables. That’s particularly the case in retrofit, where we have no control over the existing construction and we need to be careful about what we do to the structure to avoid introducing moisture problems.

    In new build construction, we tend to have a good idea of what works, especially if following prescriptive solutions. In that case, there’s no need for complex calculations. BS 5250, the code of practice for moisture in buildings, has guidance about when different calculation methods ought to be used.

    An analysis of water content over time

    A consistent layer of thin internal insulation can help to manage moisture

    Using hygroscopic, capillary active and vapour open materials helps to maintain a wall’s ability to dry to the inside. Generally, the thicker the layer of insulation applied to the inside, the harder it is for that drying to happen. Most people are now using 40mm, 60mm, or possibly 80mm of wood fibre insulation, and that seems to work okay in most places. A continuous layer of 40mm of insulation, with thermal bridges resolved, is much more effective than a thicker layer of insulation that’s hit and miss.

    Our podcast with Martin Twamley discusses this subject in more detail.

    An internal wall insulation strategy from Steico

    Using WUFI can stress test a construction

    Good practice when doing a simulation is to include moisture loads or moisture stresses. This is something WUFI allows the user to do which simpler calculation methods can’t. It’s possible to allow for a certain amount of rain coming in through a crack, or a certain amount of warm air moving out through the airtightness layer.

    Find out more

    Greengauge

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  • HPH375: A day in the life of a builder – with Mike Whitfield

    HPH375: A day in the life of a builder – with Mike Whitfield

    Mike Whitfield shares his experience of running a local construction company that specialises in Passivhaus. He explains how the business is structured, and what tasks are tackled on a daily and weekly basis.

    Interview with Mike Whitfield

    Mike Whitfield, the owner of Mike Whitfield Construction, began his career in his early twenties, working in America, Canada, and Australia. He had always wanted to be a carpenter and learnt about timber frame building whilst working abroad. Returning to the UK in the 1990s he got involved in oak frame construction for a while before rekindling his interest in energy-efficient buildings. The AECB was a great source of information to keep at the vanguard of green building, and so Mike was well placed to take on Passivhaus building when it came on the scene. 

    Mike has been a guest on the podcast before when he helped us identify the traits of a good builder.

    There is a demand for Passivhaus builders

    Once Mike Whitfield began to focus on building high performance homes it naturally led to more of this type of work. So from 2010 onwards nearly all his projects were to Passivhaus or EnerPHit. As these projects require a greater attention to detail and high quality workmanship, over time Mike Whitfield Construction has built up a reputation of being able to deliver.

    In fact, as they are seen as the go-to Passivhaus builders in Herefordshire, Mike even believes they may have missed out on jobs!

    “If you get a reputation for being too busy, you can miss out on jobs. People say I didn’t bother asking you, because you’re always busy.”

    A core team of people is key to his way of working

    Mike explains that he has a core team of people employed by his company. This is different to the typical British builder model, which uses self-employed subcontractors on ‘zero hours’ contracts.

    Being part of a regular team makes it possible to develop skills and knowledge, which is essential to a Passivhaus project.

    One of the advantages of being a well-established company is that Mike has built up a network of additional collaborators, from architects and groundworkers to electricians and consultants. It all helps the operation run smoothly.

    A local builder can often end up wearing many hats

    Mike is now 67 and trying to step back and hand over the reins to others.

    This has been an interesting process because he’s been able to contrast where the business is today, as it moves to become employee owned, versus how he started as a sole trader.

    In the early days, as is common with many small builders, the paperwork gets done in evenings or over weekends (which means working long hours each week).

    As a more established company of 11 people today, Mike has been clear that there needs to be more than one person stepping up so the load can be shared in a more sustainable way.

    There’s now a slightly different structure in place. For example they’ve got two site foremen, with one taking on more responsibility for liaising with the clients, and the other one able to concentrate on the construction. An office manager is also in place to handle the paperwork and order materials.

    Maintaining momentum requires good communication and organisation

    Mike’s work has changed recently now the foremen are taking on more responsibility. However, even with the new structure the same key tasks need to be completed.

    There’s a briefing on site at the beginning of the day so that each team member knows what needs to be achieved and can get to it. There’ll be various aspects for the foreman to oversee, such as the quality of work, the progress, and receiving deliveries.

    There’ll be meetings with the client or consultants, always looking ahead to the next steps.

    And in the office there’ll be various ordering and invoicing.

    “It’s just a question of keeping the materials flowing to it, making sure our office manager knows what’s going on and our office management system is working well. In my previous life I was on site at 7.30am to get people going, then in and out of the site hut organising things. I’d be lucky to do an hour or two of the practical work before leaving at 3.30 to go back to do a couple of hours work in the office.”

    Mike prefers a ‘collaborative procurement’ process

    Drumming up new business can be a process that takes years. It might start with a phone call from a potential client, who is looking for a plot of land. Mike would normally refer them to the architect he works with most frequently. It might go quiet for a couple of years, and then finally the discussions about the design begin.

    Costing a new scheme draws on data from previous projects

    Mike has detailed records for the outputs and costs for each stage of a build, so he can input prices at the design stage. He calls it a collaborative procurement, rather than doing a tender or some other method. A lot of architects in the Passivhaus world now accept that it can be good to find a builder you like and trust, and just work up the price with them.

    “Working from a basic sketch we can have a good go at pricing the build using our previous experience and our pricing programme. If we know the client’s budget, we can work with that and assess what is possible for the money. Mutual trust is important.”

    The team must always be working on a project

    One of the trickier elements of being a builder is keeping a steady flow of work for the whole team.

    Mike describes the ideal scenario being where their groundworkers have started the next project, whilst his team is on the main project, and maybe one or two people are second-fixing the last project.

    Of course life doesn’t unfold perfectly and sometimes they have to do things differently.

    Mike shares an example from last year when he had two jobs running in parallel. Luckily, they were only a few miles apart from each other, which helped.  

    A builder will often have a site on standby for quieter times

    When there are gaps in the schedule Mike can move the team onto one of his own projects. He says last year they had three jobs, totalling £1.5 million, in the pipeline but couldn’t start any of them. So having a plot as a fallback option means they can divert resources to do part or all of the build. Again, in a perfect situation the team would be completing the whole project in one go, but they could just do the groundworks and pause, or they could get the shell watertight and then bring things to a halt.

    Building to Passivhaus standard demands more from a business

    In Mike’s experience, Passivhaus building requires more attention to detail and greater supervision, and the profit margins are tighter.

    Although there is a lot of job satisfaction in delivering high quality buildings there is no doubt it is much harder than simply complying with building regulations. For a conventional build it is relatively easy to find a good site supervisor, use a quantity surveyor for pricing or give drawings to a builder’s merchant for them to work out the quantities you need. Mike has always had to do his own pricing and recognises it is harder.

    Want to see how a timber frame project comes together? Check out our Buckinghamshire Passivhaus case study in The Hub

    Track record is the best way to gauge a builder can deliver a Passivhaus

    Mike thinks that clients who commit to building to Passivhaus standard have thought a lot about what they want, and therefore the service needs to reflect this. In the early days people would realise part way through construction that they’d taken on the wrong builder and they weren’t going to get a Passivhaus at the end.

    It’s slightly easier now because a builder should be able to show you a portfolio of certified Passivhaus projects. If they’ve only completed one or perhaps just do ‘Passivhaus principles’ then this may be the point to ask a few more questions.

    Pricing up retrofit projects is challenging

    Although there is demand for retrofit projects Mike says they are certainly trickier. They’ve tackled 4 or 5 so far, and it took until the fourth one for them to make any money. There is an argument for doing them on a ‘cost plus’ basis as you don’t know what you’re going to find before you start.

    However Mike generally prefers to work on a fixed cost basis, with everything agreed at the start and then its up to him to bring it in for that price. It can mean tight margins if prices spiral after you’ve quoted, but on the whole it works well.

    It’s easier for builders to upskill today

    As Mike gradually steps back from the business he reflects on his career in a positive light.

    Some aspects of running a building company are tough, especially on your own, but he has always loved the craft of the work.

    To others who want to follow in his footsteps and build to Passivhaus standard, Mike says that the good news is that there is a lot more information and training available compared to when he started out. It will demand more from you and your team, but if you’re up for a challenge and committed to this way of working it can be extremely satisfying.

    “It is hard to find the right people, but if you can, and you’re all working together, it is so much easier.”

    His advice to young people starting a construction company now is to find men and women who share the same goals as you, so you can form a team to share the workload and support each other.

    Find out more

    Mike Whitfield Construction

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  • HPH374: Building for People – with Mike Eliason

    HPH374: Building for People – with Mike Eliason

    Mike Eliason talks about his book, Building for People, and the massive opportunity we have to create better places through being more intentional and thoughtful.

    Mike Eliason (photo credit Heather Eliason)

    Interview with Mike Eliason

    Mike Eliason is a researcher, writer, urbanist and architect. He is also the founder and principal of Larch Lab, a socially responsible firm working at the intersection of the climate and housing crises. Based in Seattle, Mike is the author of Building for People: Designing Livable, Affordable, Low-carbon Communities.

    A year working in Germany laid a foundation for Mike’s career

    Based in Freiburg, Mike was part of a wide variety of projects: detached houses, multi-family housing, some public work, some laboratory work. He lived in a suburb that was heavily pedestrianised, and which he describes as, “the quietest place I’ve ever lived.” And he got to know the districts of Vauban and Rieselfeld, where self-build, multi-family housing, Passivhaus and mass timber construction were all present.

    The concept of Baugruppen (“group build”; involving residents in decisions to foster community) was also well underway. Even though Mike was not absorbing these ideas fully, he felt a desire to take them back to the USA. Many of those memories have come to the forefront for him in the years since – and the ideas are finally starting to become more mainstream, two decades after he was first exposed to them.

    New development needs a rethink to shift its priorities

    Mike’s work started by advocating for better multi-family housing, similar to what he found in Germany. That connected him with a broad network of advocates and politicians who want to achieve better housing and public developments. But they don’t have resources they can show to elected officials and say, “This is how things can be different.”

    The book aims to ‘formalise’ what good looks like, and support advocacy work by adding to the broader discussion of how development in the USA needs a fundamental rethink to prioritise public health, community, affordability and sustainability.

    He sees the problem playing out in Seattle, where transit infrastructure is being redeveloped without open space, without affordable housing, and without features to mitigate the urban heat island effect or deal with storm deluges.

    Housing in the USA is not fit for purpose

    There is little variation in housing, with no real breadth of options between townhouses and large multi-family apartment buildings. Compared to the rest of the world, Mike describes the USA and Canada as “an anomaly” in this regard.

    He believes that often it’s like living in a hotel: corridors down the middle of large buildings, with units either side. The units are really deep with a window at only one end (“like living in a bowling alley”), unless you’re fortunate and live on a corner. The buildings are not climate adaptive – there’s no opportunity for cross-ventilation, and solar protection is not a common feature.

    The units tend to be large, which makes them unaffordable, but with only enough space to fit two bedrooms. If the designs tried to accommodate a third bedroom, it would have no window. “Really, they’re designed for roommates rather than families,” says Mike.

    Floor plan for Larix, a proposed six story Point Access Block, allowing for family-sized homes, units that cross ventilate, and bedrooms positioned on the quiet side of the building (Credit: Michael Eliason/Larch Lab)

    Achieving better outcomes starts with a better vocabulary

    Mike describes the lexicon that people have for talking about housing and buildings in the USA as “stunted.” Feedback about his book often centres on how it has opened the reader’s eyes to certain concepts, which he attributes to expanding the vocabulary people can draw on in those conversations.

    In structuring the book, Mike pulled together concepts he was already researching and writing about, in a way that tried to make sense of them all. That led him to including topics like low carbon housing, eco district design, human centred places, and nature and open space.

    Proving concepts can start with a single home

    While the aspiration is to apply the concepts to large developments and entire districts, they can be just as readily pulled together in a single development – even just one house.

    Development in the USA is antithetical to outcomes like being community-oriented, being adaptable and climate resilient, and providing comfort and protection. While that remains the case, it’s important to highlight the differences compared to European housing as a way to explain why the outcomes are so different.

    Passivhaus and mass timber have demonstrated that change can happen

    People in North America talked about Passivhaus for years. But until there was a tangible project to use as an example for politicians, architects and developers, it was hard to show why it was better than the status quo. Mike has experienced the same with mass timber, for which he is a big advocate. Now mass timber projects have been constructed, others can see and feel the difference.

    Freiburg’s car-light Vauban ecodistrict is filled with numerous Baugruppen (photo credit: Payton Chung)

    Ecology, affordability and community are at the heart of eco districts

    The concept of an eco district is about developing places where people can live a low carbon lifestyle and thrive. Often, they are developed on brownfield sites (Vauban was a former military base, for example).

    At its simplest, an eco district is a place where you don’t need to drive to accomplish daily tasks – they are walkable and bikeable, with low-traffic streets. They prioritise green and open space, there is more opportunity for community, and they are low stress. “Imagine an entire neighbourhood that isn’t prioritising the car?” says Mike. “It doesn’t really exist in much of the USA.”

    Another common feature is a higher level of affordability, to create a good social and economic mix. In the USA, there are token affordable housing projects but it is mostly market-rate housing.

    US arterials and highways are the types of streets where dense affordable housing is legal (photo credit: Michael Eliason)

    Planning around cars is not conducive to people-friendly places

    Often, developers in North American cities will just build parking because they think it’s what the market requires. Even transit-oriented development contributes to the problem. Districts then become very car-centric, and public health, open space, nature and community are not priorities.

    There is some connection between reducing the number of cars and enabling places to be a little better, but it’s quite a ‘chicken and egg’ scenario. Mike feels it needs a developer to say they want to do a district with no cars, then prove that the model for a car-light place is possible.

    One developer in the USA, Culdesac, is building multi-family developments that don’t require parking. Instead, they provide spaces for the community to walk in – pedestrianised streets or alleys, places where cafes can spill out, where community events can be held, or you can just run into your neighbours. It’s harkening back to a way of life before cars became the overwhelming mode of transportation.

    Creativity should be at the heart of regulations

    Regulations can either be written more creatively, so they permit or incentivise new ideas rather than block them. Or they can be written in a way that encourages people to respond to them more creatively. Mike sees this creativity as essential.

    “If we’re just pumping out the same thing over and over again … okay, we know how to do it, and we can maybe do it well, but it might not be the right thing for somebody else. We need places that offer more variability.”

    In the USA, for example, most cities have residential zoning that only allows detached houses. Multi-family housing is impossible, because it’s illegal! By contrast, Brussels has a regulation requiring Passivhaus, and provided incentives and support before the requirement became effective. And France has a 50% bio materials mandate for new construction, which is driving more straw panel and mass timber buildings.

    There are so many solutions to improving housing affordability

    The Netherlands does small districts of self-build housing with around 15 to 30 lots. The cost of infrastructure and management is lower because they’re paying the city rather than a developer, and the city is not seeking a profit. The houses are all designed and built by different people and, in Mike’s words, “the neighbourhoods are amazing. They’re incredible. We should be doing more of that in the USA.”

    The Baugruppen model is a hybrid between market-rate development and cooperatives or even social housing.

    Mike is a fan of cooperatives, especially the Swiss model for them. It uses a cost-based rent that has created some of “the most fascinating and innovative housing” that he has ever seen.

    The Mietshäuser Syndikat – the rental house syndicate – came out of Freiburg while Mike was living there. An umbrella organisation effectively co-buys multi-family property with the tenants and owns it in common. The building then can’t be sold without everyone coming to an agreement, because it’s a 51/49 ownership split. Everything is managed by the residents, who contribute to a solidarity fund to help grow the organisation and help other entities develop projects.

    However, the lack of variability in the USA – with very little public housing, cohousing or cooperatives – means it’s going to take a lot of support to grow that ecosystem.

    Operable exterior shutters prevent unwanted solar gain in summer, and provide additional privacy year round (photo credit: Michael Eliason)

    Housing that responds to climate change is essential

    Understanding the impacts of a changing climate is essential. How do we deal with the sun and overheating? Wildfires and smoke? Rain and floods. For this reason, Passivhaus is the starting point for any project that Mike works on. He loves Passivhaus because it’s comfortable and balances high tech and low tech. If you need heating or cooling, it’s the smallest amount possible.

    Gaskets and tape help to keep out cold drafts, moisture, and wildfire smoke.  (Photo credit: 475 High Performance Building Supply)

    More rain will lead to more mould in properties, and Passivhaus de-risks mould to a greater extent. In extremes of heat and cold when you lose power and can’t run cooling or heating systems, Passivhaus increases survivability. Mike cites studies in the USA where buildings designed to the minimum standard of regulations were only habitable in a deep freeze situation for half a day at most. After that, pipes started to burst. Whereas a Passivhaus was relatively warm and habitable for several days.

    The climate is an issue whether you live in a bespoke, detached house, or a multi-family building. All of these things are going to affect people, so understanding the most optimal ways to adapt or mitigate the effects is really crucial.

    A people-first street in Vienna’s Seestadt (photo credit: Lukasz Karnas)

    Better housing can also help to address social isolation

    The IPCC has previously talked about the benefits of cohousing and other forms of community-oriented housing. It’s not just that you know everybody in your building, though that day-to-day social connection is important. If you’re also designing a building together then you have similar values and things that you’re prioritising.

    There’s a fundamental difference between developing huge, anonymous buildings with 200 or 300 units and smaller buildings. It’s easier to know people and easier to ensure that people are okay if there’s a climate event. Many people who died in the heat dome event in the Pacific Northwest were elderly residents who didn’t have a social network, who didn’t have people who could check on them.

    We don’t need to reinvent the future

    We already have what we need to create better places. Active solar protection, Passivhaus buildings, low carbon construction all exist in the world. Mike’s message is that, “we can use our imagination to reconfigure them to the condition, spaces or places that we would like, but we don’t have to reinvent the wheel. Everything that we need to build low carbon places already exists. We just have to really prioritise them.”

    There’s a huge network of people who already know how to do so many of these things, who talk about different ways of building and living. Finding ways to tap into each other’s knowledge and experience is crucial. Then, we can start to change the status quo bias, and the attitude of, ‘things have been this way forever, so why change it?’ By spreading the knowledge about what is possible, we can provide shelter that is moderately affordable, so that, as a society, we can stay connected and stay in the community.

    Find out more

    Larch Lab

    Mike Eliason on LinkedIn

    Buy Building for People: Designing Livable, Affordable, Low-carbon Communities

    Transcript

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