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  • HPH400: Three couples build a terrace of three Passivhaus homes

    HPH400: Three couples build a terrace of three Passivhaus homes

    Bill Butcher and Chris Herring, founders of 21 Degrees, share details of their own group build, a small terrace of three homes in Marsden, West Yorkshire, designed and built to Passivhaus Plus standard.

    Bill and Chris on site

    Interview with Bill Butcher and Chris Herring

    Bill Butcher and Chris Herring, founders of 21 Degrees, have been proponents of the Passivhaus standard since delivering the Denby Dale masonry cavity wall project in 2010. Always open to another challenge to keep them young, Chris has his eyes on being inside his own Passivhaus home before he turns 75 next year. There’s also a community aspect to this because it involves three couples, three homes, one terrace and navigating it all collectively. This is a story about making something happen: pulling on decades of expertise, finding the right people, keeping costs down, and proving that modest, high-performance homes can be built affordably when a skilled group commits to working together.

    Existing stable block on the site

    Taking calculated risks on land can unlock development opportunities

    Chris and Jan purchased a piece of land on the edge of Marsden for a community project, but they also knew there might be development potential for an old stable block on the site. By accepting the risk, they positioned themselves to propose a solution that served both housing and community needs. And even if they didn’t get permission they had a use for the site. In other words they were managing the risk.

    Shared values give strength to the group build

    The Mount Pleasant Self-Build group formed around a common belief in modest, sustainable living. As Chris explains, he and Jan did not want to live in ‘splendid isolation’, seeking instead a community connection. Having worked with Bill for years, he and his wife Jean became obvious potential neighbours.

    “Chris and I have been metaphorically married for the last 35 years!” comments Bill.

    Both Jean and Jan were keen that their partners realise the dream of living in Passivhaus homes after spending so much of their careers trying to drive up standards in construction.

    Jan had also worked with Veronika a lot, knew that she had been looking into eco housing, and so again bringing in Veronika and Ondrej just seemed to be the perfect fit. Another key aspect of this group was their trust for each other and knowing that at certain stages of the project it made sense for certain individuals to lead.

    Emotional resilience is as vital as technical skill in group builds

    Jan noted that when one person feels overwhelmed, there’ll be another positive voice in the group. That way the speed of progress or challenges they face don’t feel so bad.

    Trust in making decisions collectively

    Chris described the Quaker concept of discernment where decisions are reached collectively. You do not always have to decide individually but can listen to others. This collective trust allows for difficult decisions to be made without fracturing the team. Without this support, Jan admitted that she and Chris might not have been so keen to tackle this.

    The planning application was a ‘best guess’ at what would be approved

    The group chose to stay within the existing footprint of the stable block to minimise visual impact. They also nestled the building into the hillside to keep the ridge height down, dropping the floor level by 1.8 metres. The new building would be clad in timber which is the same material that was used for the stable block. This low visual impact was referenced favourably in the planning decision, although it wasn’t the only consideration. Being sensitive to the context may have helped in this scenario.

    Digging into the ground and fitting their designs into an existing form does have an attached cost, but with this consent as a fallback position, there was the option to return to the Local Authority with revised designs closer to what they want. However, the downside is all the extra time it would take, possibly another year, and already two years in they were just keen to move on.

    Mount Pleasant self build plansDownload

    Keep an eye on planning policy changes

    The site occupies semi-degraded land at the edge of the village within the Green Belt. However, it’s defined as a subset called ‘grey land’ which is a relatively new planning policy update. A local landscape architect supported the application on the basis that such land lacks potential. Building housing here protects the edge of the village while meeting housing delivery requirements. It highlights that not all green belt land is equal in terms of planning policy. So understanding the specific definition of ‘grey belt land’ might provide opportunities for development.

    Fabric efficiency + renewables makes sense

    Most of Bill and Chris’ experience with Passivhaus relates to fabric performance, Passivhaus Classic in other words, but they have come around to the Passivhaus Plus category over time. This delivers everything that we’d expect from Passivhaus Classic, drastically reducing energy use, but also incorporates renewables, so that the building meets all its energy needs over the course of the year.

    Chris says decarbonising the grid alone is not enough. The focus remains on reducing energy demand for the lifetime of the building. Renewables act as a complementary layer on top of these efficiency measures.

    What may look like waste can often be reused

    Although the existing timber stable block could not be retrofitted into a new building it had a much brighter outlook than being thrown on a bonfire. Jean listed it on Facebook Marketplace which resulted in immediate interest from a farmer, who came to dismantle, transport and re-erect it elsewhere. The concrete base was also going to be crushed and reused as hardcore for the new parking area. This approach saved disposal costs and reduced the embodied carbon of the project. It serves as a reminder that a little time and curiosity can find value in waste. Demolition should be viewed as a resource recovery phase rather than just removal.

    Site access constraints can sometimes impact how you build

    Chris initially favoured off-site timber frame for speed and risk reduction. However, the roads to the plot are often narrow, with twists and turns, and so bringing articulated lorries through these villages was bordering on the impossible. After going through various options Bill got chatting to Mike Whitfield on a motor-biking holiday in Wales and was persuaded that using their stick-build approach with Masonite I-joists would be perfect here.

    Nick Grant, Passivhaus Consultant and co-author of The Good Building Book

    Early value engineering simplifies design and controls costs

    Nick Grant is the Passivhaus Consultant on this project and throughout his career he’s tried to highlight what early value engineering can bring to a project. With this reputation it made absolute sense for Bill and Chris to lean in. They wanted to make their scheme as affordable as possible and part of that was avoiding complexity. In some ways Bill and Chris even saw this as a learning opportunity because Nick Grant, builder Mike Whitfield, services engineer Alan Clarke and structural engineer Andrew Collinson are the dream team! They have been able to pare things down over the years because they work together often, trust one another and can speak openly if they can see opportunity for improvement.

    Collaborative humility between designers and specialists improves outcomes

    A local architecture firm was engaged on this project. Their skills with space and design would still be required but they were open that they had no Passivhaus experience. Chris saw this as an opportunity for them to learn and develop skills. The key was humility and recognising what the team did not know. Where architects understand Passivhaus, designs are less costly to deliver. However, with so much Passivhaus experience on the rest of the team, in this scenario it was a great move.

    One benefit of a group build is to take advantage of individual skills

    If you’re tackling a build collectively then there’s a good chance you’ve got some useful skills up your sleeve. For example, Jan is a conveyancing lawyer and so in the early stages she was able to drive through the land acquisition, divide up the plots, and negotiate with neighbouring landowners to tidy up boundaries. With the technical design Bill worked on the junction details to minimise heat loss. He’s also well versed with the construction phase and quite at home with co-ordinating the project. The rest of the group understand this skillset and just let them get on with it!

    Bill and Chris as foundation work gets underway

    Leveraging long term relationships reduces overheads and manages risk

    The project pulls on every favour and relationship built over thirty-five years. The Green Building Company team will handle on-site construction with Bill and Chris project leading. Self-managing the build is an obvious choice here. Drawing on in-house expertise for MVHR and triple-glazed windows contributes to cost control. Bill notes that if they cannot do it for a reasonable price, few others can. Currently they are hoping to deliver the project for under £3,000 per square metre. Bill says that from general chat at last year’s AECB Conference a typical figure for a one-off Passivhaus might be more like £3,500 per square metre.

    The foundations are prepared

    Staged financing requires careful cash flow management

    In terms of finance the plan involves mortgaging their existing homes rather than selling up. Chris comments that the cash flow will be tight at certain moments but they know what they have to do. Navigating finance before knowing the full cost is a familiar tension. Timing is everything when staging the drawdown of funds. This approach requires discipline to ensure the project does not stall. It is a reminder that financial planning is as critical as architectural design.

    This is an opportunity for a younger generation to get on the housing ladder

    Bill highlighted that Veronika and Ondrej are getting their first home through this scheme. With massive challenges for first-time buyers this illustrates another way of thinking, that an older generation can bring younger people into these projects. The conventional housing market offers working people almost no realistic path. Demonstrating that Passivhaus Plus is achievable at the upper £2,000s sends a vital message. Modest houses built well at a price that doesn’t require a fortune are possible. This intergenerational transfer of opportunity is key to housing sustainability and sets a precedent for future collaborative developments.

    Find out more

    21 Degrees — Supplier of all key elements for Passivhaus Plus and low energy buildings: MVHR, windows, airtightness products, specialist insulation, air source heat pumps and photovoltaics.

    Green Building Company — The independent construction team carrying forward the building expertise developed over nearly two decades within Green Building Store (now 21 degrees)

    Mike Whitfield Construction — Specialists in stick-build Passivhaus housing who are assisting with the methodology and frame installation for this project

    Hawdon Russell Architects — the architecture lead on this project who are also upskilling in Passivhaus

    Transcript

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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

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    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

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  • HPH360: Why MVHR maintenance and servicing is important – with Richard Hollas

    HPH360: Why MVHR maintenance and servicing is important – with Richard Hollas

    Richard Hollas from 21 Degrees explains why regular MVHR maintenance and servicing is essential, what it entails, and we accompany him step-by-step as he services a unit.

    Interview with Richard Hollas

    Richard Hollas, a commissioning and service engineer for 21 Degrees (formerly Green Building Store), details the process of servicing an MVHR unit, using Ben’s system as a case study. 21 Degrees supply a range of products and services for Passivhaus and low energy building projects. The team can take you through the whole process for MVHR systems; including the design, supply, installation, commissioning and servicing, and emphasise the importance of each step in this process.

    There is a difference between MVHR maintenance and servicing

    Richard starts by outlining the difference between the maintenance practices we can do as homeowners and the need for servicing by an engineer. MVHR maintenance should include changing filters every 6-9 months, cleaning air vents and possibly cleaning the heat exchanger every 2 years. An MVHR system should be serviced by a qualified engineer every 3-4 years to prevent issues like increased noise levels, condensation, and reduced airflow. A service will inspect the sensors and fans, remove any contamination, check air flow rates and make any adjustments to ensure the system is working efficiently.

    Changing the extract filter in the kitchen

    It should be easy to access your MVHR unit

    Ben’s unit is in his garage and Richard explains that this is the case for about 20% of MVHR units. The best location is in a utility room or plant room with space around it. This means it’s always simple to maintain or service the machine. Putting an MVHR unit in a loft is not ideal because it will be out of the way. You also don’t want them to be in a bedroom or other main living space as there will be some low-level noise from their operation.

    A service is also an opportunity to double-check the installation

    Richard explains that during the first full MVHR service he will check that the unit has been installed correctly. A common problem that arises is that the Armaflex insulation has not been installed. This is an extra layer of insulation that goes over the ComfoPipe, which is required by regulation, and so would need to be added.

    MVHR service: step by step

    Richard uses Ben’s MVHR system as a case study to take us through the service process:

    1. The initial system checks

    Richard begins the service by looking at the status of the system in the installer menu. He checks to see if the fans are going at different speeds, which would indicate a blockage somewhere in the system. The fans on Ben’s system are working well. He then puts the system in service mode, which stops the fans, moves the bypass flaps to the right position to allow him to open the unit.

    2. Examining the inside of the unit

    With the front off, Richard uses his torch to examine the inside for contamination and notices that the sensors are dusty, but otherwise everything looks good.

    Richard points out the bypass flaps, which are activated by the external temperature. At a certain temperature, these flaps come down, so that the air from outside doesn’t hit the heat exchanger and come straight into the house. As these are modulating ones, they will partially open and so allow the air to mix together. There is also a preheater for frost protection, if the temperature goes down to zero this will come on to stop the unit frosting up inside. The main box is the heat exchanger itself.

    Alongside this is the circuit board, that is controlling the fans, bypass flaps and other elements, so it all works together. Richard needs to access the board to detach the preheater for inspection. The preheater can become clogged with insects, creating a blockage which will then affect the air flow. Even though the unit is sealed, sometimes contamination will occur. When changing your filters make sure the unit is on filter change mode, which turns the fans off to ensure that debris is not pulled off the filters into the machine.

    Contamination on the extract fan

    3. Cleaning the supply fan and extract fan

    Although the supply fan will get a clean it’s usually in a really good condition already, whereas the extract fan will almost always have contamination. It is important to remove the extract fan for cleaning so that debris doesn’t drop into the bottom of the unit. Bottle brushes are ideal for cleaning the fan as most of it is dry flaky material that can easily be removed.

    4. Testing the condensate drain

    A small amount of water is put into the condensate drain to ensure it is draining freely. Moisture is coming into the unit from our day to day living and needs to travel through it, hit one side of the unit and then drain away. Water damage on one side of the unit would indicate a blockage.

    5. Cleaning the sensors

    Richard explains that the sensors are monitoring conditions, such as temperature and moisture and that it is really important to keep them clean. If they build up with dust they may give false readings (or even trigger an error message) which will affect the efficiency of the unit. For example, if the sensor that monitors external temperature is giving the wrong information it will affect how the bypass flaps are working and impact the preheater for frost protection.

    The heat exchanger is removed and cleaned

    6. Cleaning the heat exchanger

    The heat exchanger is a box that the air flows through, so providing it is kept free of contamination it will keep working. A regular service will prevent a build up within the heat exchanger and ensure that it is easy to remove for cleaning.  Richard describes how a heat exchanger left for 5-10 years may become so contaminated that it is almost welded into place and won’t come out at all. If that happens a new unit will be needed.

    7. Resetting the system

    Once the fans and heat exchanger are clean they can be re-inserted, and everything can be plugged back into the circuit board. When the front cover is back on, the filters can be changed and the unit can then be switched back on. The first thing it will show is an error triangle as it carries out an analysis. Richard explains that it will check the bypass, the sensors and preheater to ensure it has been reconnected properly and that there are no faults. This will also happen any time the unit switched off and then on again.

    Richard and Joe check an extract valve

    8. Checking the air flow and vents

    Richard checks all the vents for contamination around them and for excessive dust in the ducts. The air flows are also checked to ensure they are meeting building regulations. Richard is able to remove the vents and valves for cleaning without changing the original valve settings, as these have been set with locking nuts and are very difficult to change by accident. They should therefore be the same as when they were commissioned.

    Bathroom extract fans often have the most contamination

    The extract valves can get a build-up of contaminants in the kitchen from cooking and the bathroom from towels and skin but any contamination generally settles around the valves and doesn’t enter the ducting system. Richard has used a camera down ducting on several occasions to check for contamination and each time it just looks like brand new, as the filters are working to remove any bits before they reach the ducting.

    Richard points out how the supply valves can have a ring of dust around them, but that it is not coming out of the vents. It is to do with the air pressure, as the air comes out of the vents and meets the air in the room the dust settles and this can easily be wiped off with a duster.

    Richard uses an anemometer to check the air flows in each room to make sure the air flow is meeting building regulations. He can feel that the air flow is good and the readings show that Ben’s unit is achieving 50 cubic metres in the kitchen on speed 2, which is what it needs to achieve at speed 3. This shows that the unit is doing well and there is good ventilation.

    Richard can also check his readings against the commissioned figures. If one valve is the same it is likely that they are all correct and with locking nuts in place there should never be a need to recommission them. If you didn’t have locking nuts in place and someone altered one valve, say from 5 mm to 10mm it would change the air flow and so affect all the other valves.

    The extract valves are the most important ones when you’re measuring air flow during a service, because things could build up and potentially cause a blockage further down. This is unlikely to happen with the supply vents, because air comes through the filters first. If Richard doesn’t have the commissioning figures, then he will be looking to hit building regulations and make sure the system balances out.

    If you’re one of our Hub members, Chris Herring explains how to get the best value from high performance windows

    MVHR can automatically deal with excessive humidity

    Richard is sure that Ben will not have any problems with condensation as his Zender Q unit has a humidity protection setting, which will have been put on during commissioning. This means that if humidity reaches 75% in the house the fans will gradually speed up to remove the excess moisture automatically.

    A service is an opportunity to recap information with the homeowner

    Richard tells us how it can be hard for customers to take in all the information about their MVHR system at the start. They may just have had a heat pump fitted, under floor heating and a whole range of new products. He suggests having an MVHR service after the first 12 months, so everything can be checked and he can go through all the workings when it is less stressful. This develops a relationship and also gives homeowners the chance to ask questions.

    Without regular servicing the unit may start to develop problems

    When the service schedule is neglected it is likely that contaminants will build up. This could cause a conflict in the machine. For example, the fans might speed up to clear the air but this would then activate the noise guard, which is there to protect the house from noise. This would result in your fans slowing down again, and you may start to notice condensation. The unit is then not running at optimum efficiency and not performing well. It is much better to establish a regular maintenance and service programme to ensure your MVHR system works well for as long as possible.

    Find out more

    Visit the website of 21 Degrees

    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 the transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

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  • HPH331 : What is a mechanical services engineer? – with Alan Clarke

    HPH331 : What is a mechanical services engineer? – with Alan Clarke

    Alan Clarke explains the role of a mechanical services engineer on a low energy house build, in designing a heating and ventilation system that works efficiently and is affordable.

    Interview with Alan Clarke

    We’ve been fortunate enough to have Alan Clarke on the podcast before. Back in episode HPH062 we discussed with him whether a Passivhaus needs a heating system. In a later episode, he also explained the designs for the heating, ventilation, and hot and cold water systems for Ben’s own self build.

    Today, we welcome him back to conclude our mini-series, looking at different professions that we may need on our self build or retrofit project. Alan is a mechanical services engineer, with particular expertise in Passivhaus buildings.

    Most mechanical services engineers will have a background in engineering

    A mechanical services engineer will cover the design of the heating and ventilation systems of a building. Some practices would also do M&E (mechanical and electrical) or MEP (mechanical engineering and public health) work, which would cover all of the building services. As well as the heating and ventilation, that will be the electrical services, drainage and plumbing too. The majority of people practicing it professionally would come from an engineering training background.

    Relevant parts of the building regulations are Part L and Part F

    Part L of the building regulations covers the energy of the house as a whole, including the heating system. An electrical installer would be expected to be qualified and understand how to install a system that is going to be in line with the wiring regulations and building regulations compliance. This might include energy modeling of the building too.

    Part F of the building regulations is to do with ventilation. Ventilation systems in houses are relatively new, and there isn’t quite the same level of qualification and supervision.

    Pre-planning is the ideal time to involve your mechanical services engineer

    Not all architects will be familiar with integrating a mechanical ventilation system so that it works efficiently and is easy to maintain. There would be some spacial requirements at Stage 3 of the RIBA Stage of Works, but pre planning is the ideal time for an engineer to come in and think about where the main items of equipment are going to be located, and how the distribution through the building will work. Consideration also needs to be given in the design to accommodate the ductwork, although the detailed design for that would come later. If it’s for a Passivhaus, there will also need to be PHPP energy modeling at this stage, before the planning application goes in. This will have an impact on the form of the building, window sizes, etc.

    It is important to make sure the overall system is efficient

    The energy efficiency of the overall system can be broken down into separate parts:

    • The MVHR unit – this must be an efficient piece of kit with good heat recovery efficiency and quiet, efficient fans. If the fans aren’t quiet, people won’t use it.
    • Good ductwork design – fan performance can be scuppered by putting in ducts that are too small, which means the fans have to work harder. They use more energy to run, and you get more noise. A good approach to the design of the ductwork is therefore important.

    A further consideration in the Passivhaus analysis is heat loss, looking at how long the ducts are, and also how well insulated they are. Ideally, these should be as short as possible, just one or two metres length, which has implications on where to position the MVHR.

    An MVHR unit also needs to have regular filter changes. Therefore, there’s no point putting it somewhere inaccessible, where you can’t see what you’re doing!

    There are two main ducting systems

    The basic principles of a balanced mechanical ventilation system, are to bring in and supply fresh air to the rooms where we spend the most time, and take out stale air, particularly from the smelliest and wettest parts of the building. The extracted air passes through the MVHR which has a heat exchanger. This transfers practically all the warmth from that extracted air to the incoming air. Ductwork connects the ventilation unit to the rooms in the house.

    A radial system uses lots of separate ducts that run to each room. If you want more air to go to or from a particular room then you run two ducts. Also, if it’s got a long way to go, you might increase the number of ducts to a distant room to make it easier to get air from there to the MVHR.

    The other system used is a branched system. You start with the biggest duct at the MVHR and run to the first room. At this terminal, it tees off to another room before branching off again, and so on. The duct size reduces as you go along.

    Generally, the radial system ducts will have a diameter of 75 or 90mm, which is easier to thread through than the branched system, but you do need more of them. The branched system starts off at around 150-160mm, before dropping down to 100mm for individual rooms.

    Space for the ducting will need to be allowed for in the structural and architectural design of the building, so it’s good to know what system is going to be used as early as possible.

    Air should be supplied into the rooms in a way that you don’t feel a draft

    For a flat ceiling, there would normally be a disc in the ceiling that spreads the air horizontally so that you don’t feel it blowing on you.

    The other type of supply valve is designed to go in a wall. This also spreads the air horizontally. The air flows are relatively small and mix with the room air quite quickly, meaning it’s unnoticeable to occupants.

    Around 2.5 litres of moisture is generated into the house per person per day

    This is produced in a number of ways, such as:

    • Breathing and perspiration – this accounts for around a fifth of the moisture that we put in the house
    • Bathing – not just the hot water steam but also the towel and bath mat will continue drying back out into the room too
    • Water evaporation from the dishwasher drying cycle
    • Cooking – such as steam from boiling water
    • Laundry – drying washing indoors can mean there are several kilos of moisture that have to go somewhere

    Without some way of extracting all this moisture, that’s a lot of water that is just sitting in our houses. It can however be extracted through ventilation. Even on a wet day, the water vapour content of the external air is relatively low, and much less than the air indoors. Simply by bringing it in and exhausting the same volume of inside air, you can expel the water vapour.

    Part F of the building regulations has guidance for calculating the ventilation flow rate that’s needed. This is inferred from the number of bedrooms. A Passivhaus calculation is more specific and done on a per person basis.

    It is more efficient to run the ventilation constantly

    Many houses in the UK have intermittent extract fans, which just draw the vapour out when you have a bath or shower. Evidence shows however that this isn’t effective in reducing humidity levels enough, leading to condensation and mould potential.

    A house with an MVHR does focus on the wet areas, but has the ventilation running all of the time. There’s not much to be gained by turning it off, as you’re not losing any heat through it. Keeping the low power fans running continuously, rather than being off and then having to work hard for a while, is more energy efficient.

    The primary benefit is to our health

    Through living in an enclosed space, we generate a number of pollutants, some of which are a side effect of the moisture. The condensation and mould can be extremely detrimental to our health. Even at lower humidity levels dust mites can prevail, causing allergic reactions and asthma.

    By ventilating a building we can also dilute and remove the VOCs and chemicals in the air that inevitably come out of the products.

    Heat pump systems need to be designed carefully

    Traditionally, a gas boiler with radiators has been a fairly resilient system for heating. Also, it’s one which doesn’t need too much oversight from an installer or heating engineer.

    Although a Passivhaus only requires a small amount of heat, this will need to be delivered somehow. Alan commonly specifies heat pumps these days, however, he stresses that they must be designed and installed well.

    Put a hot water cylinder where you are going to be using your hot water

    It sounds obvious but is an important consideration. Positioning the cylinder centrally to where the hot water will be needed in the kitchen and bathrooms, means that you can have shorter pipe runs. Subsequently, there will be less heat lost through the pipes, and the hot water will reach the taps more quickly.

    Most of a mechanical services engineer’s work is before construction

    A typical day for a mechanical services engineer might involve:

    • A discussion with the client to understand their requirements and how they might live in their house
    • A review of architect’s designs
    • Planning the building services, distribution, emitters, ventilation terminals and key bits of plant on the layout drawings
    • Drawing up a specification. This is the shopping list for the contractors for the equipment needed. Also, it’s the particular requirements for the installation, workmanship and commissioning
    • Working on the drawings/revisions – looking at where ventilation and hot water kit will go, positioning a heat pump, and considering any constraints around where that might go

    When a client is building a house for the first time, the plans can sometimes evolve later in the process as they think more about what they really want. Ideally you should be executing the plans you have developed in the design stage during the construction stage, not altering them. This will make it harder for the whole team and more expensive for you.

    Your mechanical services engineer needs to understand your priorities

    They should listen and understand what their brief is. It’s not helpful to have someone come in with preconceived ideas of a technically complicated piece of engineering, when the client just wanted something simple. It’s a waste of their time and money.

    Ideally, you also want your engineer to have enough experience to be able to look back on other projects to see what has and hasn’t worked well.

    Find out more

    Follow Alan Clarke on Twitter

    Transcript

    Download a transcript of the interview with Alan Clarke

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

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  • HPH327 : Upskilling in DIY during a home retrofit – with Es Tresidder

    HPH327 : Upskilling in DIY during a home retrofit – with Es Tresidder

    As someone with no previous interest or skills in DIY, Passivhaus Consultant Es Tresidder explains why he went about changing that for his own deep retrofit project.

    Interview with Es Tresidder

    After getting a degree in ecology Es’s journey to low-energy buildings incorporated time working in an earthship, and teaching children in schools about recycling. There then followed an MSc at CAT (Centre for Alternative Technology), and a PhD on optimisation of low energy building design at De Montfort University.

    Initially sceptical about Passivhaus, his interest grew upon interacting with the ‘Passivhaus community’ on Twitter. He then completed the Passivhaus Designer course, which he credits with teaching him more about building physics in two weeks than he learnt about in the entire duration of his MSc and PhD.

    Es Tresidder now has his own consultancy Highland Passive and is in the final stages of retrofitting his home in Fort William, Scotland.

    We caught up with him in the early stages of his EnerPHit project.

    A good location can lead to a more sustainable lifestyle

    Es and his family moved to the area so they could pursue their love of outdoor activities – climbing in particular – and they bought this 1970s timber frame house as a temporary measure until they could find a property to retrofit or a plot on which to build from scratch. It was however in a perfect location for them: walking distance to both primary and secondary schools, a 5-minute walk to the train station, safe cycling routes into town, and facing out to Ben Nevis.

    If you want to retrofit, seek a property that needs work doing anyway

    Normally if you’re planning to take on a retrofit project, you’d look for a cheaper property with obvious signs of dilapidation. However, this house seemed on the face of it to be in a fairly good condition, which made it difficult to justify any extensive works. But once they started scratching away at the surface they discovered some bigger issues with damp and mould. They had also outgrown the house as it was and needed more space. So the decision was made to stay put, extend upwards and retrofit the whole house to EnerPHit standard.

    Part of the reason for Es getting hands on was that he was interested in upskilling as a professional. He wanted to learn more about the practical side of tackling a retrofit so that he could help other people who were going to do it.

    Never be afraid to get input from people with more experience

    Beyond wiring a plug, unblocking a sink and changing a light bulb, Es had very little inclination or ability when it came to DIY.

    In order to learn and upskill, he sought out people who knew more than he did and asked for guidance. His father, a retired carpenter, and a neighbour who was an experienced DIYer were regulars to call upon. Beyond that, YouTube tutorials were extremely helpful. While Es lacked practical skills and experience, he did have plenty of theoretical knowledge and a logical brain for working out sequencing and consequences of doing something.

    Jobs he tackled himself included tearing things down, pulling floorboards up, putting in the insulation and doing the airtightness, and doing the MVHR installation. He did however leave the complicated work, such as building walls and taking off the roof, to the builders!

    Make sure you have the right tool for the job

    One of the things Es learnt early on was how important it was to have the right tools for the job. Investing in a good quality drill early on for example was essential.

    Having spent a couple of weeks taking down half of a fake stone wall, initially with a lump chisel and hammer and then an impossibly heavy drill, he borrowed an SKS drill that finished the job off in an afternoon! From that point on he decided that if it was clear that there was a tool he needed, and he didn’t have it or wasn’t able to borrow it, then he would buy one. If he didn’t need it at the end of the project then he would sell it.

    Be prepared that some things may not go to plan

    On one occasion Es mistakenly cut through a mains water pipe, rather than a radiator pipe!

    A particularly difficult time was when they removed the roof, shortly before an incredibly wet May. Sadly, all the insulation Es had laid in the floors, together with the original floorboards that he had painstakingly taken up and re-laid, were destroyed and had to be replaced.

    Working alongside a building team presents challenges

    For the bigger structural changes Es engaged a local building contractor.

    As Es was keen to do the airtightness and insulation work himself, he soon realised that he couldn’t keep up with the builders.

    For example, Es hadn’t finished the insulation when the builders were ready to put up the plasterboard. The knock-on effect was jobs were done out of sequence and they were unable to do an interim air test.

    The alternative would have been to spend time upskilling the builders in how to do the airtightness and insulation to Passivhaus standard.

    “The difficulty with that, is that because this was a retrofit project, some of the airtightness was just unbelievably fiddly. And even a motivated contractor is not as motivated as the homeowner. I spent so long doing it that I find it hard to imagine that they would do it to anything like that level. But I might be wrong.”

    Another option might have been to project manage everything himself. This would mean he could book and pay for services as and when they were required. It might have got round some of the scheduling issues, but would undoubtedly have taken longer.

    This radical retrofit will lead to a healthier home

    A suggestion from a builder friend was to just put foam backed plasterboard on the internal walls. But once Es started taking the walls apart it became clear how mouldy and damp they were. Using rigid insulation wouldn’t really do anything about airtightness. It would also exacerbate the problem by making the damp areas colder and more damp.

    Es often felt during the process that what he was doing was radical. Doing it any other way though would result in inferior performance and an unhealthy home.

    Removing the roof was radical

    Taking the roof off was an expensive move, and one that Es still isn’t entirely sure was the right thing to do.

    The upstairs rooms in the one and a half storey house had very low head height due to the eaves, which meant there was a lot of space being wasted. Another problem they had was because of where their windows were located, they also missed out on incredible views to the south. Instead of looking at Ben Nevis, they faced a neighbour’s gable wall and a not particularly attractive tree.

    While the alternative might have been to extend the house rather than raising the roof, Es felt the layout wouldn’t have worked as well. They also could have knocked it down and rebuilt, but even with the VAT reimbursement, Es thinks it would have been a more expensive option.

    Raising the roof has given them comfortable internal heights of 2-2.4m, and gained useable floor area that they didn’t have before.

    DIY is time-consuming and exhausting

    Es has reached the point where he is so busy with work that, in order to get the project over the finish line, he has handed over some of the traditional DIY jobs to the builders. He has also had enough of doing them! This has included fitting the kitchen and bathrooms, and also the painting and laying flooring.

    Generally speaking though, Es quite enjoyed getting hands-on with the project and acquiring new skills. He quite likes the idea of combining a bit of manual work, or the teaching of it, with his desk-based job in the future.

    Top tips

    • Practice your new DIY skills somewhere where it’s not too critical first, in case they need refinement.
    • If you’re a keen DIYer and have knowledge of building physics then you could do a lot of the work yourself. Doing it without that theoretical knowledge though would be risky. Most people would need professional input to do a deep retrofit safely.
    • Don’t panic! Keep calm and methodical – particularly when using the very expensive and very sticky airtightness tape.
    • Have a mantra reminding yourself how dangerous power tools can be.
    • Ask lots of people for help, and don’t be afraid to use YouTube.
    • It would be worth doing a Passivhaus contractor course. It gives a good grounding of the theory, and also of some of the skills.

    Find out more

    Visit the website of Highland Passive

    Visit the website of John Gilbert Architects

    If you enjoyed this episode, you can also listen to some of our other interviews where industry professionals have taken on their own projects:

    Transcript

    Download a transcript of the interview with Es Tresidder

    Get access to our in-depth video case study of the Kinver retrofit in The Hub

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Rate and review the podcast on Stitcher

    Like our Facebook page

    Follow us on Twitter

  • HPH314 : Getting a self build over the finish line, despite setbacks – with Mike Coe

    HPH314 : Getting a self build over the finish line, despite setbacks – with Mike Coe

    Mike Coe gives a final update on his now complete Portree Passivhaus, that has seen budgets stretched, contractors disappear for a year, and a Covid lockdown!

    Interview with Mike Coe

    Mike Coe is a returning guest to the podcast. We have been fortunate enough to speak with him about his previous self build, Cropthorne Autonomous House, and have been following his progress since moving to the Isle of Skye to build Portree Passivhaus with his partner Lizzie. Having been in the house for a year now, we pick up where we left off three years ago, in episode 259 when the house was almost watertight, and find out whether Mike has managed to be as hands-off with this project as he had intended!

    Mike had always intended to do the MVHR installation and electrics himself

    He had started on the MVHR installation as soon as there was enough building there for him to work on. The main ducts that bring the fresh air in and take the exhaust air out, went in almost at the foundation stage, as they were assembled as the wall was being built that the ducts pass through. This way it meant they could be built into the wall, rather than having to cut out a large hole afterwards. He also started channeling out for power points before the concrete blocks were even up to first floor level.

    The specification of the MVHR was important for Mike as he wanted to build this house with no heating system whatsoever. They selected a system made by Nilan, which also contains a micro heat pump. It’s only around 60 or 70 watts, but it effectively aids the heat extraction process and makes it more efficient. It means that in the winter the heat pump comes on when the temperatures dictate it, making the incoming air temperature slightly warmer, and in the summer it provides a very small amount of cooling.

    Their only other source of heating is from a single bar electric fire which they’ve used infrequently, just for the odd hour here and there.

    It maintains a comfortable temperature

    The internal temperature on the night they moved in was just 11 degrees (with a raging storm and a power cut for good measure!) But once Mike got the MVHR up and running a couple of days later, and they had a week or two of sunshine, and with the effect of the two of them living there, it took just a couple of weeks for the temperature to rise to 21 degrees. Since then, they have been pleasantly surprised at how well it keeps a steady and comfortable temperature, even more so than the Cropthorne house, despite its larger form and having been less fastidious in the attention to Passivhaus detail. Mike suspects this is because of using the concrete blocks which, as well as providing the structure of the building, also act as a thermal store. He is conscious that the use of the concrete blocks and steel means it has higher CO2 emissions from the manufacture than that of a lightweight timber structure, but this was primarily dictated by the planning department.

    Mike’s previous Passivhaus experience paid off

    With a contractor and architect that didn’t have experience of building a Passivhaus, Mike found one of his roles on site being that of quality control. When it came to airtightness tape, he was able to show them how the standard builder’s merchant tapes would just tear like paper, yet the Passivhaus airtightness tape was incredibly strong and flexible.

    They didn’t mind and were happy for Mike to take on other pieces of work, such as some of the carpentry, especially as he and Lizzie were on site doing the MVHR and electrics anyway, and it meant the workload for their men was reduced.

    It took twice as long to build as planned

    The original plan was for a 15 month contract build period, but at the 10 month stage the contractor got called away to work on a 25 bedroom hotel extension, leaving just Mike, Lizzie and a freelance bricklayer to carry on with the work. This meant an incredibly frustrating almost year-long wait while the hotel project was finished, which unfortunately then coincided with the first Covid lockdown.

    “So there we were, with another three months added on to the almost year long delay due to the hotel build. The hotel extension was sitting there virtually complete, but they couldn’t open it because of everything was shut down because of Covid, whereas our house was nowhere near complete and nobody could work on it except me.”

    Mike managed to use that time as productively as possible to keep the project moving forward. Without being able to access new building materials as the merchants were closed, he dismantled some of the temporary stairwells that the contractor had put in so he could use the timber for building the stud partition walls. He used all the plasterboard that was laying around that he could, rescued timber that had been thrown out and used that for the stud walls, and also managed to build a new desk. Psychologically he found all this beneficial as it felt like progress was still being made.

    In total, the project took around 30 months to complete.

    Money became very tight

    With the planning department selecting the most expensive option, they always knew that the budget was going to be tight. In addition to the overruns caused by the lockdown, a number of other bills came in that caused them to go over by £34,000. This included £8,000 to install a water pipe from the mains halfway up the hill, rather than being able to connect from the supply of the neighbouring bungalow that they owned and were living in, and £750 for a tree survey to make sure that the pipe wasn’t going to damage any tree roots!

    As they were running out of money and with cash being tied up in the neighbouring bungalow until it was sold, they had to take on more of the work than they had ever intended to do. Mike had been unimpressed with the plumber who had done the first fix, so ended up rectifying some of his work and also did the second fix plumbing. This meant he plumbed the washing machine, kitchen sink, dishwasher, and the fit-out of all the bathrooms.

    With great reluctance, as it is a job he and Lizzie particularly dislike, they also ended up doing most of the decorating themselves.

    One year on, there are problems to rectify

    Having been in the house for a year, they are currently in the snagging period where the contractor will rectify some of the problems that crop up. Their contract allowed them to withhold a small percentage of the total payment, which will be paid once these have all been sorted. However, there are other problems which Mike intends to take on himself.

    The door in the lower ground floor porch was never properly adjusted and would stick and not shut fully. When he got round to looking at why this was, Mike discovered that it was actually causing a serious damp problem. The damp had resulted in the hinges corroding, with the adjustment screws for the doors then being impossible to turn.

    Something else that Mike will need to tackle, is an issue with the windows leaking. As they weren’t a standard specification that the contractor was familiar with, they installed them but weren’t confident to set them up, instead leaving this to Mike to organise. However, with all the other jobs and distractions going on, this got pushed lower down the list. With the driving rains they receive, several of the windows subsequently leak. Thankfully there are no serious structural leaks though, and when all the adjustments to doors and windows have been carried out then hopefully that should be an end to those problems.

    During a period of extremely high winds recently, part of the zinc capping that goes around the roof parapet was torn off. Fortunately it doesn’t threaten the structure of the house in any way and it’s still watertight, but it’s something else to add to the list of jobs.

    He has some carbon-saving projects lined up

    Now that they have freed up their cash by selling the neighbouring bungalow, and once Mike gets over a certain amount of self-builder fatigue, he is keen to make headway on some other projects.

    The first is installing a PV array that will make the house run more efficiently, as it will contribute to hot water and charging their new electric vehicle.

    He is also in the early planning stages of putting a micro hydro generator (a little water turbine) into a stream that runs down through their site. If it works it will likely only generate around 100-150 watts per day, but that will be for 24 hours a day and virtually through the whole of the year.

    He is adamant this will be his last self build!

    Now he and Lizzie are able to reflect on their journey, they are able to say that although lots of things went wrong, they managed to get them corrected. Although they did have the benefit of experience from their previous self build, there were still new problems that this project threw up that had to be dealt with. Overall, Mike says they are pretty happy with the end result, just not necessarily with how they got there.

    Find out more

    Visit the website of Portee Passivhaus

    Follow Portree Passivhaus on Twitter

    Follow Mike Coe on Twitter

    Catch up on previous episodes with Mike Coe

    HPH259 : Constructing the masonry superstructure of Portree Passivhaus

    HPH220 : How to finish a self build when money is tight

    HPH152 : Should you consider the resale potential of your self build

    HPH054 : Building an autonomous house

    Transcript

    Download a transcript of the interview with Mike Coe

    How relevant is mass?

    Es Tressider is a guest on the Building Sustainability Podcast, talking about whether adding mass to a building will make it more energy efficient.

    Please connect with us

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  • HPH305 : Building a Passivhaus with cross-laminated timber – with Mick Woolley

    HPH305 : Building a Passivhaus with cross-laminated timber – with Mick Woolley

    Mick Woolley explains how the use of timber was a key element of his award-winning Passivhaus bungalow.

    Interview with Mick Woolley

    For the last two years, Mick Woolley has been living in his Larch Corner Passivhaus which was the Small Projects winner in the 2021 UK Passivhaus Awards.

    His self build journey began following the loss of his wife. He had long held an interest in self building and took the attitude “what could possibly go wrong!”

    To watch the documentary about Larch Corner go to PassivhausSecrets.co.uk

    He broadened his search area

    Initially beginning his search in the south east of England to be closer to his two sons in Surrey, Mick found a lovely plot, surrounded by a vineyard, and just 30 miles away from them. But despite the proximity, it had taken an hour and a half to get there and was £450,000 before he’d even knocked the existing bungalow down. It was at that point he decided to abandon his search in the south east and opened up to looking at sites as far afield as North Wales and Cornwall.

    They made changes to the planning designs

    Mick saw a plot on RightMove, that seemed to be in a pleasant village location at the northern tip of the Cotswolds. Close to a National Trust garden and Stratford upon Avon, he felt he would be able to find enough to do in the area and was surprised when he managed to purchase it for around the guide price at auction. It came with planning permission for a single storey Passivhaus with a design that he admits probably didn’t appeal to everyone, and is why he thinks there wasn’t more competition in the bidding.

    Although not put off by the design, he was sceptical of its Passivhaus credentials and enlisted Mark Siddall of LEAP to re-work the plans. He did however want to keep it a bungalow to make it accessible for a family member who uses a wheelchair, but also because it future-proofed it for him too.  

    The original design had a lot of corners so they removed some of these and also had to raise the roof to ensure there was adequate head height for insulation. They swapped the entrance hall and study around to ensure a better flow into the house, and took out the many corner windows from the plans. Mark instead designed an arrangement of windows that came in 2 sizes: smaller ones for the bathrooms and bedrooms, and larger windows with seating elsewhere.

    Timber was an important element of the design

    Mick wanted to build using Cross-Laminated Timber (CLT), as much for the visual impact it provided inside as for its structural qualities. The bungalow uses 17 sections of spruce timber, which have 6 layers, are edge-glued, and don’t require an airtight membrane around the outside.

    The roof came with a cassette of insulation in it so the structure went up in two days, and had an airtight wrap over the top by the end of the third day. The walls are made of an I-frame structure with blown-in wood fibre, giving a thickness of around 600mm and a U-value of 0.1.

    The exterior of the bungalow has larch cladding.

    The foundations were pre-cut to size

    The building has a Jackon XPS foundation which was pre-cut to the required size and slotted together, with an XPS upstand that locked into the perimeter. This created its own formwork for the concrete pour.

    The flat roof has a camber of around 5 degrees for shedding water. On top of the insulation is a cold roof section of ply and bitumen that provides the finishing structure on which to put the green roof. Mick says he checks up there from time to time just to check that seedlings for trees and other unwanted plants haven’t blown in and taken root!

    He was keen to be hands-on

    With Mick being on-site throughout the build process he was keen to get involved in any way he could, so one task that he took on was the airtightness taping. His top tip for getting it into the corners is to ideally bend the tape in two in order to push it in and get good contact right the way through the junction.

    The straight lines of the 17 sections of CLT only took an hour to do, but all the other joints around the doors and windows took a lot longer!

    Mick employed Alan Clarke as his M&E engineer and he carefully designed the ventilation system so it could go through cupboards and be kept out of the way, but still accessible if needed. The full design with all of the MVHR kit was supplied as a single delivery, and Mick took on the installation of the pipework himself. Not having any experience of doing something like that, he did find it took him a very long time to put together!

    There is around 140 square metres of floating floor, which was designed to be laid to flow through without any junction strips at doors. His builder Andy took time to work out the geometry to ensure that boards were centred and wouldn’t end up with slivers at the edges, which Mick was then able to lay.

    Always make space for storage!

    Although Mick was adamant that he wanted to use CLT, he now realises that he could have been more efficient with materials and created the timber finish that he was looking for by using large sections of three-ply timber.

    If he were to do the build again, he would probably opt for a two-storey building, though still keeping a downstairs bedroom. He says that the UK housing stock is generally fairly deficient in terms of providing for the elderly and those with mobility problems, so designing at least one bedroom downstairs is really important.

    Mick says that going for a two-storey design would improve the form factor and use a lot less insulation. It is also more efficient in having less foundations and roof.

    Lack of storage space is often a real problem in typical new build homes, but Mick is delighted at the amount of space they designed into his home, including a large storage wall. He also has a double garaged sized shed, although this is currently housing lots of off-cuts of CLT and three-ply materials that are waiting to find a home!

    He emphasises why it’s always a good idea to build into the loft as that’s also potential space that can be used for storage.

    Images copyright Mark Siddall LEAP

    Find out more

    To watch the documentary about Larch Corner go to PassivhausSecrets.co.uk

    Check out the website of LEAP

    Follow Mick Woolley on Twitter

    Follow Mark Siddall on Twitter

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  • HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    Ben Adam-Smith shares his own experience of living with a mechanical ventilation system. While he’s clocked up a few error messages on the unit and had more problems than most, he explains why he wouldn’t want to go back to natural ventilation.

    MVHR is a key component of low energy buildings

    In case you’re wondering what MVHR is, well, it stands for mechanical ventilation with heat recovery.

    As buildings become increasingly airtight, a good ventilation strategy becomes all the more important.

    But there’s a clever twist: by controlling the ventilation you can recover the heat when you want to (transferring it to the fresh incoming air).

    Hopefully that’s clear, but if not we made a documentary about airtightness a few years ago!

    Since this documentary was made I have moved into my own Passivhaus.

    Error messages are warnings

    I am a big fan of MVHR (pun intended) but that doesn’t mean I’ve had the best relationship with my MVHR unit.

    I’ve had 3 sets of errors on the machine in the two and a half years I’ve had it.

    The first errors might have been in connection with a silencer that was retrofitted a year after we moved in. I suspect the machine was clever enough to notice something had changed. The errors resolved themselves!

    About a year later, an external pressure message cropped up a number of times.

    The fan status readings on fan speed two which should be 200m3/hour are:

    Supply fan – Speed 550rpm, Duty 15%, Flow 93% ( a noticeable drop in air flow)

    Extract fan – Speed 1900rpm, Duty 48%, Flow 0% ( air flow can be detected from the extract air valves when a piece of tissue is held up to them )

    Error messages can be reset

    Interestingly, these errors can be reset while you’re investigating the cause… but they usually return, even if that is weeks later.

    Apparently there was a known issue with the humidity sensors on my particular unit. This was changed and again it was business as usual.

    However, at the beginning of the year a new error cropped up!

    Nobody likes seeing a flashing red light on their control panel because it means something needs fixing (or at least investigating).

    At this particular point we’d been getting night-time temperatures between -2C and -5C, which is the coldest we’ve experienced since we built the house.

    When the temperature warmed up a little I was able to reset the error and everything would return to normal (or until I could get the machine looked at).

    However, that trick didn’t work the next day.

    The machine completely died and I couldn’t get it to come back on. There was also a light burning smell inside the house.

    I had a couple of concerns at this point:

    • How long will it be until I get my machine back up and running?
    • Might I get a build up of mould somewhere in my system if I can’t get it fixed soon?

    Fortunately when it comes to mould, I was quickly reassured by my friends in the know.

    So, now whilst the problem was investigated we had to survive without the machine.

    With no MVHR running, we resorted to opening windows!

    Not that I’d choose to do this experiment but it was quite interesting to see the impact of living in a Passivhaus with no MVHR running.

    Firstly, the house remained nice and warm inside (the insulation has gone nowhere). Perhaps the heat wasn’t as even; I don’t know. But it wasn’t a terrible experience.

    It was however, a right faff to have to open the windows every few hours… not to mention the heat we must have wasted… and the family complaining at having the windows open when it was freezing outside.

    Perhaps the most interesting impact of no MVHR was the instant lingering smells. My wife noticed that each room had its own smell! And it was definitely harder to shift cooking smells.

    Eliminate the simple stuff first

    On a chat with Steve Clarke at Green Building Store trying to diagnose the problem, we double-checked that power was getting to the unit.

    Embarrassingly I hadn’t even checked the trip switches. In fact, we’d managed to cover them up with a shelving unit so that I’d forgotten they were even there!

    With the machine humming to life, I had a massive sense of relief. Whatever the issue is it’s not quite so urgent when the system is at least on.

    The preheater needs to be replaced

    It didn’t take long to diagnose the problem (the burning smell was the preheater working for the last time) but British wisdom of leaving the EU meant the new preheater took several weeks to get here.

    The warranty period on MVHR units is typically 2 years

    For an essential item for Passivhaus dwellers, this does seem short.

    The clock also starts ticking when you buy it.

    Mike Coe, the self-builder behind Portree Passivhaus, bought his unit in advance and subsequent delays have meant it will already be out of warranty.

    My own unit was out of warranty, too, but the manufacturers kindly supplied the new part free of charge.

    I installed my new preheater!

    With Steve Clarke from Green Building Store on the phone, I was expertly talked through what I needed to do.

    Buying through a company with good customer service was a great move.

    We’ll have to wait for more cold weather to check it has done the job.

    ‘MVHR needs to be as reliable as a fridge’

    I was interested to see whether other people had had trouble with their units and so I posted up on social media.

    I don’t believe many Passivhaus owners have actually had problems, which is a good sign. As Fionn Stevenson says ‘good quality assurance is essential’.

    Andy Simmonds, Chief Executive of the AECB, stressed it is such an important piece of kit. The emphasis needs to be on durability, reliability and repairability.

    He likened an MVHR unit to a fridge.

    Having bought a new fridge when I built the house I have noticed that even fridges have got more complicated.

    In the past it’s normally the plastic door seal that has failed before anything else, but on the new more complex models water dispensers get jammed on and ice trays freezer up, and don’t get me started on the plastic water filters!

    I would not go back to ‘natural ventilation’

    Despite the inconvenience of investigating different error messages, my MVHR unit has never stopped! Yes, I was a bit slow to check the trip switches, but if there’s a next time I won’t make the same mistake.

    If the machine is still operating, you haven’t got a big problem

    If your machine is not working at all – i.e no ventilation whatsoever – then I would really be looking for a speedy repair.

    As with anything in life that breaks, it normally takes a little while to fix it.

    So it would be lovely to have the option of a 24-hour repair service in the years to come.

    Transcript

    Download a transcript of this podcast.

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  • HPH284 : Build It magazine’s Self Build Education House – with Calum Taylor and Opinder Liddar

    HPH284 : Build It magazine’s Self Build Education House – with Calum Taylor and Opinder Liddar

    Calum Taylor and Opinder Liddar talk through the design and construction of the ‘Self Build Education House’ at Graven Hill.

    Interview with Calum Taylor and Opinder Liddar

    Calum Taylor is the owner of Build It Magazine, the longest running self build magazine in the UK. Together with their website and exhibitions, their aim is to provide expert advice and information in a practical and down to earth manner, to help self builders make the difficult decisions as easy as possible.

    Calum has been working on Build It’s Self Build Education House at Graven Hill with Opinder Liddar. Opinder is a director of lapd Architects. They are based in Oxfordshire and specialise in residential projects, particularly for self builders.

    It is a showcase of possibilities

    Coinciding with Build It magazine’s 30th anniversary, Calum’s idea for the Self Build Education House was to showcase the possibilities available to self builders by demonstrating the processes and some of the products that can be involved in a self build journey, whether or not they themselves were building at Graven Hill.

    It would also be a great experience for Chris Bates, the magazine’s editor, to have hands-on involvement with the project management.

    The house has been built on the Graven Hill development

    Graven Hill is a ground-breaking development: the first of its kind in the UK. The land was formerly owned by the Ministry of Defence before being sold to Cherwell District Council to develop. The site has planning permission for 1800 new homes, up to half of which are designated for self build.

    Calum says it has its fair share of cynics however, who question the plot sizes as being more like developer plots.

    “But I think it’s incredibly important that for self-build to really become the norm in the UK as opposed to what is done by a relatively few, relatively wealthy people, that we need to look at different models and we need to look at how you can have fantastic housing on smaller plots of land. And if you can do that with the profit on the land going back into the local community via the council then that strikes me as being a perfect model.”

    The plot passport outlines the parameters

    A number of plots had been allocated for show home use and, following a tender process, Calum successfully won a corner plot around the back of the houses featured on Grand Designs: The Street.

    Each plot comes with its own “plot passport” which defines certain parameters, such as maximum height and the footprint of where the house needs to be. With those established, the design can begin to develop as a response to the site aspects.

    It needs to work as a showcase, and a home

    In five years’ time the function will change from show house to a home that will be lived in, and this consideration formed part of the brief. It needs to have enough space for people to walk around in, while still feeling like a home.

    “Primarily we want people to look at it as ‘I want to live here. This is an amazing house.’ We don’t want them to think, ‘this works very well as a museum.’”

    With a plot restriction of 160m², the design was put in for planning at a size of 150m². The Graven Hill calculations don’t include basements and void spaces, so together with a basement plus an attic that would be prime for conversion, the overall area is closer to 230m².

    The budget has been for high-end specification

    Calum explains that the budget is rather difficult to define, as it’s not being constructed in the usual way. Typically a similar house might cost £2,000 per square metre, or around £470,000 in total. But as Build It’s complete guide to the house highlights, you could build the same size of house for substantially less if it wasn’t to the same high level of specification.

    By adding in the expensive finishes and details, Calum explains that it is giving people the opportunity to look at where they want to be spending their chunks of money.

    The corner plot dual aspects led much of the thought about design

    Opinder also likes the aesthetic of a steep roof pitch on a house, and to make a dramatic feature of the front he designed two gables, with the feature continuing around to the side.

    Insulated Concrete Form (ICF) was chosen as the construction method for a variety of reasons: it has good energy efficiency, is very airtight, performs well acoustically, and was particularly well suited for constructing the basement.

    Following discussions with Nudura, their ICF supplier, Opinder decided to push the design and show the materials at their best. The resulting design has a balcony that projects over the car parking area, hanging off a cantilevered wall that flies out at the first floor level. There are also frameless windows that turn the corner and are taken up to the underside of the gables.

    The ‘wow factor’ was an important consideration

    Often the space required for a plant room is underestimated, so the Build It house is a good example of showing how much area can be needed. Their plant room is in the basement to house the mechanical ventilation with heat recovery (MVHR) system, along with the inverter for the solar panels, battery storage, water softener, control hub for the Niko smart home system, and the amplifiers for the whole house sound system.

    Calum wants visitors to have the ‘wow factor’ when they walk in, so Opinder has designed a triple-height entrance hall. There you are greeted by a sculptural ash staircase that winds its way up. The eye is also drawn through towards the back of the building and the garden.

    A mixture of door types have been used, with pocket doors that slide into the walls, and a glass screen that gives the flexibility of sub-dividing the open space if needed.

    There is further architectural interest on the ground floor, with a curved wall that comes around from the cloakroom and into the kitchen, next to the floor to ceiling windows that give an amazingly light and spacious feel.

    The ground floor is open plan with lots of hard surfaces, but the oblique angles stop it from being acoustically noisy.

    The timber posi-joists, which are great for running services through, can be prone to noise transfer, so they have used acoustic boards, acoustic insulation and a screeded floor on top.

    On the first floor there is a glass balustrade which further enhances the connection with the outdoor space.

    Each bedroom is individual because of the different aspects and how they sit within the roof forms.

    It has been a typical self build journey in many ways

    The project hasn’t been without its challenges along the way.

    Calum explains that many of the difficulties have been in the project management of coordinating suppliers and contractors to work together.

    Issues were with communication, building to the same tolerances, and even incorrect measurements on site meaning that windows and doors didn’t end up exactly where they should have been.

    His tip for self builders is to keep on top of checking things like that because you could be storing up problems for a later date if things aren’t nipped in the bud as soon as possible.

    “The problems are about people and communication and scheduling things and dealing with the weather and all of those little curve balls that come your way and how you can actually try and continually pull it back to keeping it true to the vision of what you’re trying to create and as originally in the plans. Because it can be quite easy to deviate off slightly and end up with a house that doesn’t quite look and doesn’t quite perform in the way that you hoped it would.”

    The house shows what can be achieved on a tight plot

    With Calum working on the house from a Project Director level, it has been Editor Chris Bates who has been project managing the self build, going through the hard learning process and gaining valuable lessons and insights from it.

    Regular readers of Build It have been following the journey in the magazine and have been visiting to see the finished building. And for other members of the public with no prior experience of it, there are infographics around the house that help them understand the journey and the choices that were made around materials and suppliers.

    Going forward, the house will be paramount to the magazine’s editorial, as they can relate back to the experiences and decisions they made, or what they might have done differently in another scenario.

    Although the house went over budget and needed their contingency fund, (primarily due to weather delays), Opinder is keen for the house to show what is achievable on a fairly tight plot. He says it shows that it can be attainable for everybody and offers a genuine alternative to buying a typical “Noddy-box” house.

    More Graven Hill podcasts

    We’ve been following the Graven Hill scheme with interest for some time, so if you would like to know more about the background of the project and what it’s like to build there, then check out some of our previous podcasts:

    Find out more

    Visit the website of Build It magazine

    Follow Build It on Twitter

    Find out more about lapd Architects

    Please connect with me

    Subscribe, rate and review the podcast in iTunes

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  • HPH280 : A beginner’s guide to the Passivhaus Standard – with Jon Bootland

    HPH280 : A beginner’s guide to the Passivhaus Standard – with Jon Bootland

    Chief Executive of the Passivhaus Trust, Jon Bootland, explains the processes and benefits of building your house to the Passivhaus Standard.

    Interview with Jon Bootland

    When Jon Bootland finished his university degree he began his employment first as a building services designer, and later working on good practice for sustainable low energy buildings, now with nearly 30 years experience. He has also been involved with the Passivhaus Trust since it was formed back in 2010. With initially very slow progress since the first Passivhaus was completed in the UK in 2010, numbers are now increasing rapidly at around 1,200 completed buildings (of which around 200 are individual owner-occupied homes), with another thousand already in the pipeline.

    Carrowbreck Meadow – Image copyright Jefferson Smith

    There’s nothing hugely complicated about Passivhaus

    The origins of Passivhaus come from Germany, where the physicist Wolfgang Feist wanted to find a way of making sure that high performance buildings actually delivered on their claims, and performed the way that they were designed to do.

    “It’s all about building physics. There’s nothing hugely complicated about it. It’s just what do we need to do to actually make it work and do what we said it was going to do.”

    High in comfort levels, low in energy use

    The fundamentals of a Passivhaus are:

    Insulation – This is an important part of reducing the energy required to heat the building. A typical Passivhaus might have up to 30cm of insulation, meaning that the walls will be very thick.

    The building fabric and airtightness – The other parts of the building will also need to have a very high performance. Windows for example will need to be triple glazed with good quality frames and careful detailing about how they fix together. The airtightness of the building is important with the aim being to stop draughts coming in and heat leaking out.

    Ventilation – Because the building is now free of draughts, attention then needs to be paid to how to ventilate it. A mechanical ventilation system is used (MVHR) to bring fresh air into the building, while recovering the heat from the outgoing air.

    As well as dealing with keeping the house warm in winter, Passivhaus formulae also look at the sun and other heat sources coming into the building and how the ventilation and insulation can work to keep it cool in the summer.

    Old Holloway – Image copyright Juraj Mikurcik

    Have a Passivhaus expert in your team

    Jon says that building a Passivhaus is harder to do than a normal house, but that doesn’t necessarily mean you have to employ a team of specialists. He would however recommend having someone in your team that does have Passivhaus training, and preferably experience. It doesn’t have to be the builder, but could be the architect or a consultant.

    The Passivhaus Planning Package does the calculations

    You will need someone who knows what they’re doing to fill in the Passivhaus Planning Package (PHPP) and work out the answers to the calculations with you. It is a tool that takes a holistic approach to making all the elements work together, to make sure you end up with a building that has the performance and comfort that you are looking for.

    There are benefits to having certification

    PHPP should be used right from the beginning to look at the size and shape of the building, the window locations, balconies or anything else that might penetrate into the building etc. A certifier is able to check what is being put forward and advise on whether what you’re suggesting is actually going to work in the way it is intended.

    Without having a certifier on board you will not be able to call it a certified Passivhaus, which does have some value in being able to sell the project. Certification is the best way of ensuring that your building will meet the required standards and provide the comfort and energy performance that you are looking for. If you’re not planning to use a certifier, then Jon recommends ensuring your team of architect, builder and consultants have plenty of Passivhaus experience between them to give you confidence it will perform as intended.

    There are health and cost benefits

    Jon outlines some of the key benefits of a Passivhaus:

    Lower energy bills – The extra insulation and airtightness means less heat is escaping from the house, and therefore less energy is needed to heat it. Typical heating bills for a standard sized Passivhaus might be around £100, compared to several hundred for a non-Passivhaus equivalent.

    Health benefits – Jon says there are research projects planned in the next few years looking into this, but there is still plenty of anecdotal evidence from occupants talking about the health benefits of living in a Passivhaus. As well as thermal comfort, the air that comes in can filter out air pollution and pollen, and people have reported improvements in asthma conditions. The mechanical ventilation also reduces moisture levels in the building which prevents condensation and mould.

    Some construction methods will be harder than others

    Jon says that although you could achieve Passivhaus with any construction type, it will be harder to achieve with brick and block for example than with timber panels. Although it’s possible to do, it will just need to be approached differently.

    The extra outlay is money well spent

    Jon uses social housing to get comparable benchmarks for how much more a Passivhaus will cost to build over a standard form of construction. Typically the additional cost of building a Passivhaus will be around 4-8% higher. Jon says that probably half of that is just on better quality building, which actually should be applied to all new buildings anyway, regardless of whether they’re Passivhaus.

    So on a £200,000 – £400,000 build cost, that’s likely to add on just £8,000 – £16,000 extra.

    “So, say you’re going to get a much better quality building that will make you more comfortable, more healthy and will perform better for 50, 100 years or more, it’s a very small amount of money in my book and it’s a much better way to spend your money than on a super flashy designer kitchen.”

    There are ways to keep costs down

    The shape and form of your building is crucial in keeping the costs down. Adding on multiple wings, outlying parts, differing floor levels, balconies additional roofs, lots of corners and odd shapes, will all make it more difficult to make a Passivhaus work, and will be more costly.

    Jon wouldn’t recommend everyone try and build a square box as being the answer, but the closer you aim to a square box shape the easier it is to achieve Passivhaus.

    Another way to keep costs down is to bring in your Passivhaus expert as early as possible. Don’t wait for the design to be finished and then call them in to do the calculations, but involve them at the design stages to help develop the building shape, window sizes and locations etc.

    Multiple heating sources are not needed!

    Jon explains that it can be challenging mentally to think of a house not needing multiple heat sources in it, but really they’re not needed.

    Commonly though, people might put a radiator by the front door so that as you walk in there is a perception of extra warmth, while your body adjusts from the cold outside to the comfortable 20-21 degrees inside. A heated towel rail in a bathroom is also quite popular.

    The design needs to minimise overheating risk

    With homes becoming more energy efficient, the risk of overheating in the summer is becoming more significant and has to be planned for.

    The main source of heat coming into the house in the summer will be from the sun, mostly in the late afternoon and evening. To stop the heat coming in without losing the views, Passivhaus buildings will often have some kind of shading or overhang on the west or south facing walls which keeps out the heat until later in the evening when the temperature drops.

    There are also other heat sources to take into account such as the occupants and appliances, which heat the house slowly during the day. This data also feeds into PHPP to calculate how much heat will need to be taken out of the building to keep it cool. This can be done using the mechanical ventilation, or by opening the windows, particularly overnight. The temperature fluctuation in a Passivhaus will only be a few degrees, compared to 10-15 degrees in other houses.

    “But the extra insulation and the extra performance of the windows, the doors and so on helps in the summer. Just as much as it helps in winter in keeping the heat in, in the summer it keeps the hot air out.”

    The Passivhaus Trust oversees the standard in the UK

    The standard was invented and developed in Germany, but in the UK it is looked after by the Passivhaus Trust. Their job is to look at how to apply and make the Passivhaus work in the UK, with our differing weather patterns and culture. Jon gives an example of these different considerations being parts of Scotland, where people don’t want to open their windows for night-time cooling because of midges coming in, so different approaches have to be developed.

    The second aspect to their work is promote the adoption of the standard, by engaging with central government, local authorities and trying to get people on board.

    Jon accepts that while it’s a great standard it’s not perfect, so the third part of their work is carrying out research on specific aspects that can be changed and improved over time.

    There are different levels of Passivhaus standard

    There are two main standards: Passivhaus Classic for new build and EnerPHit for refurbishment. The criteria for achieving EnerPHit are slightly less stringent because it is that much trickier to do a retrofit. Certain aspects of the building are fixed and can’t be changed, so an allowance is made that if you can’t change those things you can still get Passivhaus.

    The Barrel Store – an EnerPHit Standard youth hostel. Image copyright Mac McClure

    In addition there are also two new standards: Passivhaus Plus and Passivhaus Premium, which are effectively the Passivhaus Classic but with renewables. Passivhaus Plus is where the energy generated by the renewables will exceed the energy demand of the house and reach zero carbon. So the energy generated will be equal to or more than your energy used during the year.

    Passivhaus Premium takes that a step further with enough renewables to create an energy positive house, so you’re generating more than you need and reclaiming money back from the grid.

    PHPP can be used to calculate embodied energy

    Within the planning tool they are now looking at add-ons which consider the embodied energy of the materials that you use and form part of the Passivhaus calculations. This will benefit people who are keen to use natural materials or who are just interested in understanding how much embodied energy there is. Jon stresses it is not a requirement for achieving the standard, it’s just developing the capacity to do it for those that would like it.

    Find out more

    Visit the Passivhaus Trust website, and learn more about their Passivhaus goes Personal campaign

    Transcript

    Download a transcript of the interview with Jon Bootland.

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