Paul Morris from Solar-Shield explains how external shading can help control solar gains and reduce internal temperatures, keeping your home cool as temperatures rise.
Interview with Paul Morris
Paul Morris is a third generation blind maker and external shading specialist at Solar-Shield: Exterior Shading Solutions. They aim to deliver a range of different shading solutions that not only help to keep your home cool during the summer months, but provide a more constant indoor temperature all year round. In this chat, Paul highlights the benefits of using external shading over internal blinds.
Internal blinds aren’t effective when it comes to temperature regulation
Paul begins by explaining the difference between internal and external shading methods and their ability to keep the heat out of your home. When the sun shines, it transmits short wave energy which as it passes through the glass in your window is absorbed by your furniture, floor or walls and is re-radiated as long wave energy. This long wave energy can’t pass back through the glass of your windows and as a result the heat is trapped within your home, creating a greenhouse effect.
By using internal blinds, you may feel as though you are blocking the sun and therefore keeping the heat out, but the heat is still being absorbed by your blind and radiating that heat back into your room. External shading methods aim to absorb this short wave energy before it has a chance to pass through your window and to radiate it back outside as long wave energy.
“So the simple thing is, stop the sun before it hits the glass and you solve the problem.”
External shading has been popular in other Northern European countries for many years
Paul debunks the common misconception that external shading is only for hot climates and explains that countries like Germany, The Netherlands and Scandinavia have been utilising the technology for many years because they understand the principles. The UK building industry lags behind, but as summers get hotter as a result of the climate crisis, more people are beginning to recognise the value of external shading.
External shading offers year long benefits
Temperature regulation and heat reduction are often seen as the primary benefit for installing external shading. However, Paul also highlights that they don’t just act as heat gain reducers. They can also insulate, provide privacy and let you control light levels.
“So some people will have external blinds on the north facing windows, so that during the winter they can keep some of the heat in. There’s more than one benefit in using external shading.”
Building regulations now address overheating
Paul explains that there are two main markets for external shading: retrofit and new build. The retrofit market is the biggest and is often driven by the problem of overheating – people are getting too hot in their homes and therefore seeking solutions. New build homes must comply with building regulations (Part O), which considers overheating and one solution included in the guidance is external shading.
External shading can come in many different forms
External shading is not a one size fits all approach and Paul recommends looking at all of the different options to see which will be best suited to your home. External shading can be grouped into two categories: dynamic and passive (or fixed). The dynamic shading methods are ones which you can move and control, allowing them to serve different functions at different times of the day or year.
Dynamic shading methods include external venetian blinds, awnings and roller blinds – which normally use a screen fabric with an open weave that allows a view through.
Fixed shading is part of good house design and may include roof overhangs and deep reveals around windows. For example the overhang at Hazel Tree House helps shades windows from the high summer sun but still allows the low sun in during the winter when solar gain in required.
Fixed shading can also be provided by pergolas, brise soleil or even a tree – features that are there all year round.
Include external shading in your design as early as possible
When approaching a new build or retrofit project, Paul recommends considering external shading as early as possible in the design process to ensure you have the most options.
Your architect or designer should have a good grasp on this, optimising the orientation of your home and thinking carefully about the shading. If you’re building to Passivhaus standard, this is baked into the processes but the Passivhaus Trust has some excellent guidance on how to design for summer comfort.
Whatever you decide, if you look at the options early the shading can be integrated much better into your building and there will be a seamless finish.
“When planning shading, plan it early, that gives you the most options. Very often we get called in quite late, and I say to people, it’s going to be a compromise. If you want to reduce the number of compromises you make on your design, speak to people like ourselves early.”
Dynamic shading can be radio controlled
Although dynamic shading solutions can be operated manually Paul suggests automated controls, particularly as this shading is external and may cover many windows.
If you’re hard wiring your blinds then the main consideration is power at first fix.
However, if you have an existing low energy home and you’re worried about drilling through walls and insulation then there is another option.
Some external shading products have solar Li-ion batteries which means there’s no need to wire them in. They can also be radio controlled from inside.
“If we were living in Northern Norway and it was dark for months of the year, you’d get about 60 operations before your battery started to run out. So in this country, realistically, with having daylight most of the time, the battery isn’t going to lose its charge.”
While exterior shading products can be used in conjunction with smart home technology, Paul prefers to use timers and set blinds on different windows to come into operation at different times. This method does require getting to know how the sun interacts with your building, but once you have worked out the schedule it is extremely effective.
External shading is resilient to windy conditions
A common concern surrounding external shading solutions is their ability to withstand strong winds. Paul explains that all external blinds have wind ratings and combined with a wind sensor, they can be resilient in windy conditions.
External venetian blinds are stable and will go up to 17 to 22 metres per second of wind before they need to be retracted. External roller blinds have a greater resilience, whilst awnings will need to be retracted at lower wind levels. Paul recommends having a wind sensor on all external products to automate these retractions and act as a fail safe.
“No matter where you live, whether you’re on the Western Isles of Scotland, down a valley with the wind whistling up it, at the top of a hill, they’re a lot more resilient to wind than people realise.”
MicroLouvre is the top choice when it comes to sustainability
Paul recommends MicroLouvre for those looking for a sustainable solution to external shading. MicroLouvre is a passive external screen that is manufactured from 80% recycled materials. It has a 60 year lifespan and is 100% recyclable at end of life. During its life, it uses no power whatsoever and is maintenance free.
Fitting your home with external shading might cost between £5,000-£10,000
The price of external shading solutions very much depends on the size and scale of your project. Paul explains that the average order for a new build is between £5,000 and £10,000 but can be more for larger projects. While there are benefits to having external shading for your whole house in practice there is a law of diminishing returns so prioritising the problem areas first is a good approach.
“If we’re talking about a large set of bifold doors, say, 5 metres wide by 2.2 metres high, you could be looking between £2,000 to £4,000 depending on the product used.”
Tom McSherry from BuildStore explains the importance of cashflow when it comes to building a house and why a big part of selecting the right mortgage product is about planning your project around your budget and making sure you have accurate costings.
Interview with Tom McSherry
Tom McSherry is the National Business Development Manager at BuildStore with over 30 years of experience in financial services, 19 of which have been exclusively at BuildStore. With a background in engineering and a passion for construction, he has also successfully managed the development of his own family home, emphasising the importance of professional involvement in the design and construction process.
Engage early and start with a clear budget
No matter what your financial circumstances are, you will get the maximum benefit by engaging early with a mortgage provider and planning your house build around your budget. For some, the incubation period may be three or four years, and BuildStore has a specific team that will support early engagers.
Tom says that setting a clear and realistic budget is essential. Architects, designers and package solution providers should then work within these parameters, reducing the risk of a Grand Designs style ‘disaster’.
Remember the 3 ‘C’s – construction, cost and cashflow
While determining how much money you should borrow is a key stage, cashflow is the most important aspect of your finances once the build is underway. This ensures timely payments to contractors and the smooth progression of the build. Of course, all of this hinges on an accurate understanding and modelling of construction costs in the first place!
If you’re one of our Hub members, check out our training session with Tom.
Money is drawn down in pre-determined stages
Part of the planning before construction will include how much money is paid out and when. These are called ‘stage payments’ and at BuildStore there are three options:
Valuation based arrears – Payments are made when the value of your plot or property increases.
Stage payments in arrears – Money is released on completion of each stage of your build.
Advanced stage payments – Money is provided in advance and based on your costings for that stage.
There are pros and cons to each of these mortgages but ultimately it comes down to your personal circumstances as to which is more appropriate.
For example, if you were embracing off-site manufacturing for your house build then you may have some significant costs upfront.
“The advanced stage payment, the accelerator mortgages as its known, delivers the money into the customer’s bank account prior to the beginning of each stage, which allows them to pay for their superstructure in a timely fashion. And it’s a complete mitigator of risk again, you know exactly what you’re getting at each stage.”
There is a degree of uncertainty with valuation based mortgages
For this product the stage payments are based upon a valuation in arrears. This means there is no guarantee of how much you will receive at each stage, because it will depend on the independent valuation that is carried out.
Therefore for projects where the property’s value temporarily decreases after the completion of a stage — such as when a barn is stripped back during a conversion — the valuation-based model may not be the best fit.
“If I’m adding a large wraparound extension to my home, I can use the same stage payment mortgages, but of course at some point I’ll create openings in the walls to create an extended area, my property that could be worth 300,000 could drop to 150 in value, because it’s no longer even wind and watertight.”
Secure your mortgage as early as possible
Every project is different and will require a tailored approach, and so you put yourself in the best position by starting the conversation early.
Even if you plan to use cash for most of the build, still engage early
If you have a lump sum to get your project started and think that you can secure a mortgage later, perhaps during construction, then you may be in for a shock. Setting up a mortgage takes time. It may be better to work with your mortgage adviser to form a plan incorporating your own funds.
For example, you might draw down a small amount early on to get the mortgage live and then use your own funds, safe in the knowledge that you have funds in place to complete the entire build.
Draw down your money when you need it
Whilst you could borrow funds for the entire project at the beginning of the process it probably doesn’t make sense as you would be paying interest on the whole amount when you don’t need it all yet. Therefore if you draw down only the amount you need for each stage, you will be minimising these charges.
“So if I’ve got a build project, it’s going to take me 14 months, I don’t want to take £300,000 on day one and service that debt, I’d rather take £30,000 for my foundations on day one, and make an interest only payment on £30,000.”
Other ‘safety nets’ can be put in place
BuildStore not only provides mortgage advice but will keep in touch throughout the project with monthly check-ins. In addition, they offer site insurance during construction and a 10-year structural warranty which goes live upon completion.
You may also want to explore personal insurance which would cover you against changing circumstances such as redundancy, critical illness and bereavement.
Self build mortgages are temporary products
As the name might suggest this is a mortgage that helps you get through the build. Sometimes you may even choose to pay interest only.
So once a completion certificate has been issued it makes sense to switch to a standard residential mortgage, often with a free switch facility. This approach ensures clients transition smoothly to a longer-term mortgage that best suits their needs.
Make sure your mortgage advisor has access to all lenders
Tom’s closing advice emphasises the importance of early engagement and accurate budgeting in self-build projects. He advises that clients work with industry specialists who have access to all lenders and product types to avoid issues like running out of funds or delays in receiving stage payments.
“I’m not going to my GP for surgery, I’m going to go and deal with someone who knows specifically, that’s what they do day in and day out.”
Judith Leary-Joyce shares her experience of retrofitting a Victorian end-terrace house to reduce energy consumption, make it more healthy and comfortable, and leave a sustainable legacy for future generations.
Interview with Judith Leary-Joyce
Judith Leary-Joyce has a life long passion for climate justice and sustainability, being one of the first members of Friends of the Earth. This passion touches every part of her life, so when she and her husband decided to undertake an extension of their Victorian, end of terrace home, it was not long before the thread of sustainable building had been pulled and a full retrofit project was underway.
Judith and her husband have lived in their Victorian end of terrace home since 1979 and over this time have undertaken a number of renovations. But it wasn’t until they began to look at extending the ground floor at the rear in a sustainable way that they discovered the world of whole house ‘retrofit’.
“We realised, it doesn’t make any sense to stick a really good eco build on the back of a leaky house. And then after a long night of the soul, many lists, we came out saying no, we want to make the house a legacy for the future.”
Most homes a ripe for a retrofit
Judith says we must recognise the environmental impact of outdated housing and the necessity of retrofitting them for comfort, health and energy efficiency. Everything that we do has an impact on the planet, and our housing is one of the largest investments that we can influence to be greener.
“21% of UK emissions come from leaky homes. In the UK, every home built before 1990 needs a retrofit.”
Watch an entire retrofit of this mid terrace home in The Hub.
Adopt one ‘eco’ habit at a time
Judith speaks openly about how she manages to live a climate conscious life and how important it is to make small and gradual changes. Her green lifestyle includes refusing plastic wherever possible, eating vegan or vegetarian meals, banking ethically (not supporting fossil fuel companies, for example) and driving electric vehicles, but this didn’t happen overnight. Her key message is to try your best and be conscious of the impacts that your actions have on the world, but most importantly identify the areas where you might be best able to make changes.
“If you look at everything at once around climate, and it’s getting worse and worse and worse, I can get into paralysis… So my way of managing over the years has been to take one thing at a time and get to be like an eco warrior about that.”
Become an informed client
One challenge you may face with a retrofit is finding builders with the appropriate experience. Therefore it becomes really important that they buy in to what you are trying to achieve. Judith’s builder was happy to co-operate but was new to some of these principles (continuous breathable insulation, an airtightness layer, a well thought out ventilation strategy) so Judith and her husband had to ensure that they were educating themselves on the correct processes and acting as quality control.
“We had just builders, we didn’t have eco builders. And of course, they just wanted to do what they’ve always done and go down to the local building yard and get exactly what they want. We were saying, we’ve got to order it and it’ll take four days to come… That went down like a lead balloon. ”
Breathability must be maintained in old houses
For older homes, maintaining breathability (vapour openness) is essential to prevent issues like damp and mould from occurring. This influenced the choice of wood fibre over petrochemical-based products.
“It’s an old house; anything before 1930 is going to be a breathable build. So we had to be breathable and to understand why.”
Diathonite (insulated plaster) on the front bay wallInternal insulation of gable wall with wood fibre Pavaflex Wood fibre insulation under the suspended floor
Check the quality of work regularly
Judith and her husband stayed in their house while the work was carried out. Although there were challenges, such putting up with the dust and having nowhere to retreat to, they were able to be present and involved in the project.
“The real value of that was that we went round each evening to see what they’d done, and we were checking was it okay.”
Find passionate and knowledgable people to help guide you
Judith explains that not all professionals, including architects, were fully engaged or supportive of the retrofit. As a result she decided to take matters into her own hands by finding passionate and knowledgeable experts to offer advice. Judith highlights that often the best people are within the sales or tech support teams of sustainable building companies. They are often experts who are thrilled to share their knowledge.
Plan your work and then work your plan
Having a comprehensive plan before you carry out any work on site is a really good idea. Much as with a new build project, a retrofit requires a level of detail and that comes from working through the design process.
Judith has put everything she’s learned into a book
The eco renovation was a learning journey, with Judith continually researching and adapting to new information and best practices. However, she wants you to get ahead more easily. So she’s written a book called the Beginner’s Guide to Eco Renovation, which maps out the process and aims to set you up for success.
Kym Mead from Mead Consulting explains what Passivhaus certification is, how the process works and why there is a difference between certified Passivhaus buildings and those that just adopt a ‘Passivhaus principles’ approach.
Interview with Kym Mead
Kym Mead initially trained as an architect and then worked at Building Research Establishment (BRE) in the Passivhaus consultancy team. It was here that he got the opportunity to head to the Passivhaus Institut in Darmstadt and become a Passivhaus certifier, one of the UK’s first. As his role required him to do a lot of travelling, when he and his wife started a family he decided to set up his own consultancy MEAD offering architectural services and Passivhaus certification. He soon found himself swamped with certification work and so this became his sole focus.
Passivhaus certification is ‘a helpful audit’
If you are building to Passivhaus standard then Passivhaus certification is part of the process. Kym describes it as a helpful audit that is independent from your design and construction team to ensure that every action you take is working towards the goal of Passivhaus certification. Certifiers are there to provide information about the process and, with a wealth of experience, can be a great support when issues arise as they have most likely come across them before. Certifiers will also be checking the quality of your construction and will ultimately perform an evaluation to check your project meets the Passivhaus standard.
“I always say it shouldn’t be a draconian process from top to bottom, where there’s a big scary certifier saying yay or nay. It should be a helpful process. We all want to get to that same point: that certified building, and we should all work collaboratively together.”
Aim to bring a certifier onto the team early on
By bringing a certifier on board in the design phase of a project any potential issues can be spotted and remedied. The later it is left the more difficult and costly it becomes to change things.
“So if I receive an inquiry, my first question is who’s involved? Is the Passivhaus Consultant involved? Have you run initial checks through the PHPP, carried out the initial energy balance? How’s it looking, how’s it performing? Those kind of questions. And you can gauge from those answers the level of experience within the team. “
Reduce the overheating risk as much as possible
Overheating is defined by the Passivhaus Institut as exceeding 25C for a certain portion of time. The current threshold is for 10% of the year, however Kym would recommend aiming for below the 5% mark in order to make the house as comfortable as possible and to future proof your project.
Overglazing can be an issue
If your design team is new to Passivhaus it is possible they may include too much glass in their designs. This is less of a problem now the Passivhaus market is maturing but was certainly a challenge with some early Passivhaus projects.
Performance rarely improves as the project progresses
Modelling projects in the Passive House Planning Package (PHPP) is another step in the process of designing a Passivhaus. If the initial designs are only just meeting the energy targets (15kWh per m2 per annum) then this could be cause for concern. As a general rule, the performance reduces slightly through the design process. Therefore starting with a conservative goal (for example 12kWh per m2 per annum) will give you some leeway during the build for your performance to fluctuate.
Photographic ‘evidence’ needs to be submitted
Kym explains that if a client requests a site visit he is happy to oblige, but in the majority of cases there is little need. The certification process requires detailed notes, technical data sheets and pictures of the build process which the certifier can examine. A certifier will be looking at the execution of the construction. For example, is the insulation continuous?
Swapping materials last minute could cause a problem
A certifier is also checking that the designs have actually been executed on site. This includes keeping an eye on product changes.
“Contractors may think the lead time on a certain type of insulation is too long, I can get the same thickness of insulation… but the lambda value may be slightly different, which means it’s going to perform slightly differently. So, these things we need to watch out for. We need to make sure that contractors are aware that any changes need to be fed back to the design team.”
Encourage a ‘no blame’ culture
On a construction site things can go wrong. Therefore it’s important to foster an open and honest culture where team members feel safe admitting mistakes. When errors are dealt with at the time it is easier all round. If a mistake is hidden because somebody is worried about getting in trouble then bigger problems can emerge down the line when the performance is checked. This is often related to insulation and airtightness.
Engaging with a certifier keeps you on track
The vast majority of projects that Kym has worked on have gone onto achieve Passivhaus accreditation and the reason for that is that the process acts as a safety net. So when feedback is given and adopted then you move one step closer to certification.
In the unlikely event that a project is not performing it can be investigated.
“There has been the odd occasion where a Passivhaus is not performing as it should do. We’ve gone in and looked at the reasons why. It could be anything from faults with the MVHR, whether that’s human error, installation error, or just manufacturer error, you know, these things happen, we can look at that, and we can go in and fix it.”
Extending a Passivhaus could void the certification
Passivhaus certification may not last forever! A ‘material change of use’ such as extending the property, swapping the heat source or replacing the windows could void the certification.
Therefore careful consideration and analysis is necessary when there is a significant change. Think how it will affect the performance of the house.
Recertification is an option and it is unlikely that you’ll have to go through the full process again. There will just be an administration cost with Passive House Institute.
“There was a project recently and they certified to a Passivhaus. Then a year later they installed some PV. Now they re-certified as a Passivhaus Plus.”
Use the Passivhaus Trust to find a certifier
There are currently 11 Passivhaus certifiers in the UK and you can find their details on the Passivhaus Trust website. Kym says they are all lovely people but may work slightly differently. So have a chat, see who feels right for you and get some quotes. Kym tends to charge according to the size of the building and typically (at the time of releasing this podcast) that might be somewhere between £2000-£3000, for a single, modest-sized dwelling.
Last minute changes could jeopardise certification
The certifiers job isn’t to tell you what to do but to provide all the information you need to make the right decisions. Sometimes you may even choose to abandon the certification path.
“Building houses is never easy. It’s not a sort of practical thing, it’s an emotional thing as well. If it’s your house and you’re investing money into it and you want to make a last minute change, that’s your right. Our job as certifiers and consultants and architects is just to manage that. But if it is going to be an issue, I will explain the issue and if they still want to go on, and it may jeopardise the final pass of our certification, then that’s okay.”
For houses that miss Passivhaus Classic there is also the option to certify to the Low Energy Building Standard.
Adopting ‘Passivhaus principles’ is a gamble
There’s an important distinction to be made between using ‘Passivhaus principles’ versus building to Passivhaus standard. A certified Passivhaus has a strict set of criteria whereas adopting Passivhaus principles is vague – it might be good or it could be miles off.
“I’m always wary of [people] advertising ‘Passivhaus principles’. It feels like people are being a bit misleading. They’re trying to promote themselves on the back of something, but they haven’t actually adhered to the standard anyway. We’ve been doing Passivhaus for long enough that it shouldn’t necessarily be that challenging. If you don’t want to certify a building, you know, that’s up to you. Just don’t say that you’ve adopted Passivhaus principles in your building.”
Passivhaus dwellings may be worth 2-3% more
Although the UK now has thousands of certified Passivhaus dwellings it is still early days. Estate agents may have heard of the Passivhaus standard now but it is fairly rare for them to come onto the market. Therefore the Passivhaus ‘uplift’ is a slight unknown. However, Kym reckons through conversations he’s had that a certified Passivhaus might increase the property value by two to three percent.
A certified Passivhaus ‘does what is says on the tin’
Living in a comfortable house with fresh air 24/7 and low bills is what a Passivhaus delivers. There will be no mould or cold spots. These promises can only be met when a systematic approach has been taken to designing, constructing, commissioning and checking a building. Certification is yet another essential part of getting what you want.
“Passivhaus does exactly what it says on the tin in the sense that if you want a building that performs, it’s a very robust assessment and it will pretty much all the time deliver what you require.”
Lloyd Alter explains the term upfront carbon, its relevance to us all as consumers, and why he felt compelled to write a book on the topic.
Interview with Lloyd Alter
In 2021, Lloyd released his book Living the 1.5 Degree Lifestyle, where he attempted to limit his carbon emissions in line with what climate scientists say would be needed to keep within 1.5 degrees of global warming. Lloyd took on this challenge just as the Covid-19 pandemic struck and therefore it might have been slightly easier than normal because big emission activities such as flying were restricted. After completing a year living within this carbon budget, Lloyd stopped carbon counting. Habits that stuck include eating more vegetarian meals each week, using his e-bike instead of his car as much as possible, and not buying gadgets on a whim. The trickiest part for him has been air travel and he has taken a few flights since.
After examining the power of our personal choices Lloyd’s latest release focuses on our obsession with stuff! In his new book, The Story of Upfront Carbon: How a Life of Just Enough Offers a Way Out of the Climate Crisis, Lloyd explores the carbon emissions linked to everything we purchase as consumers.
“If you buy a car you’re buying 14 tonnes of upfront carbon emissions, the emissions of making that car. Everything you buy has these issues and people would talk about efficiency, efficiency, efficiency. But efficiency is pointless without sufficiency.”
What is upfront carbon?
When it comes to producing products a common phrase used to describe carbon emissions (or greenhouse gas equivalent emissions) is ’embodied carbon’. However, the word embodied is misleading in this context as it seems like it is describing a positive process of carbon sequestration rather than a harmful process of emissions. Lloyd, alongside Elrond Burrell and Jorg Chapastarted thinking if it could be described more accurately and came up with ‘upfront carbon’. This term clearly highlights to the consumer what the carbon cost has been to create a product up until the point of purchase.
Upfront carbon refers to the first 5 stages of the life cycle (production and construction) from A1 to A5 which goes from the mining of materials right up to the use stage. It can be difficult to find accurate information within different aspects of the supply chain which makes most calculations an estimate rather than a certainty. Lloyd highlights that in spite of this uncertainty, it is always a good idea to use as little resources as possible as this will reduce the upfront carbon. It is also important to focus on items that use less processed materials because the upfront carbon will be significantly lower, so a wooden pencil rather than a metal mechanical one, or straw insulation over foam.
“The ultimate thing is just how much of everything are we using”
Upfront carbon is a good place to start but can’t be the end
Upfront carbon tells us a story about the production process of that object and can highlight the impact that the mere existence of the product has on our planet. However, with many of the things we buy, we will also generate carbon emissions when we use or maintain them. The easiest example of this is a car, which comes with approximately 14 tonnes of upfront carbon, but if that car has a petrol engine with poor fuel efficiency, the carbon emissions will be ongoing. It is therefore important to be looking at both the upfront carbon and the entire lifecycle of the product, in order to understand its impact and determine whether it is worth purchasing in the first place and how best to manage it.
“I had a student who actually analysed a pencil for her class. It was a brilliant, brilliant examination because the Staedtler pencil was made in Nuremberg, from clay from Pennsylvania and graphite from Turkey and cedar from California. And all of these things came together in a pencil in Nuremberg, which was shipped to the store in Aurora, Ontario, North of Toronto. But the carbon emissions from her driving to the store and bringing it home were twice as big as the whole manufacture of the pencil and shipping everything all over the world.”
Buy good quality things and maintain them for as long as possible
Every time you buy something new it comes with upfront carbon. Every year you can make that product last, you are amortising that upfront carbon over a longer period and it will be getting less and less. Lloyd highlights this as the simplest method for reducing your carbon emissions and by breaking that consumerist mindset, you will be taking a large step towards a more sustainable lifestyle.
Use materials that have been processed less
Lloyd highlights that another way to ensure you are reducing your upfront carbon is to use natural materials where possible. The majority of building products that have been highly processed will have extremely high upfront carbon, items like foam insulation or concrete. Lloyd uses an example from Steve Webb:
“He said, how do you make concrete? You take limestone, you grind it up into a powder, you put it in a kiln at 1450°C. You then mix it with a bit of clay and aggregate to make what is basically artificial stone. So if I go to a quarry, cut out the limestone, cut it into blocks, drill a hole and put a cable through it as reinforcement, I can make a beam out of stone that is stronger than the beam out of concrete with a 10th of the upfront carbon emissions and it will last five times as long. I said why aren’t we doing this? Making concrete is perverse.”
Minimally processed materials must be used in the most efficient way and all while keeping a check on the scale of things. Lloyd indicates that there is often a misconception that if wood sequesters carbon, then using as much as possible can only be a good thing. However, this negates the fact that wood is a precious resource and whilst it is a great natural building material with low upfront carbon, it should be used as efficiently as possible within the structure.
While much of the design world ignores the wisdom of optimising, the path is clear. For example, for larger timber buildings they would be simple and boxy, and limited in height to around 6 storeys. The buildings would have flat facades and fairly small windows.
“We should stop this insane competition to be the tallest wood building in the world. You don’t want to be the tallest wood building, because then the columns are getting bigger and bigger and bigger, and you’re putting in more and more fibre. And you’ve got to deal with harder fire regulations and all of these things.”
Finding out accurate information about the upfront carbon can be difficult
You cannot accurately measure the upfront carbon of wood because every tree is different and unique. The most important thing you can do is make sure you only use FSC certified timber.
Both high energy efficiency and low upfront carbon must be prioritised
The construction space can be filled with confusing examples. Many of the first really efficient houses used foam insulations with huge amounts of upfront carbon, so whilst carbon emissions were reduced on a day to day basis, they were significant during construction. An opposing argument has been raised from within the eco build community, where natural building materials with low upfront carbon have been prioritised whilst the need for energy efficiency has been questioned. Lloyd believes that both must be considered equally to ensure that our homes are as sustainable as possible whilst also providing comfort and security.
There may be emissions from heat pumps
The refrigerants used in heat pumps often contain harmful greenhouse gases and so if the heat pump isn’t installed correctly they may leak. There are now some heat pumps that claim to use ‘natural’ refrigerants but in reality they are still fossil fuels, just natural gasses rather than fluorocarbons. The ‘natural’ heat pump is a much less harmful version and should definitely be prioritised where possible, but it is not necessarily emission free. Because of this nuance, once again, it is important that the spaces we are designing are modest to ensure that we can keep the size of our heat pump down and therefore reduce the associated emissions.
Lloyd highlights that there is a growing need to design buildings with future grid intermittency in mind. This would include low carbon, well insulated and efficient shells in order to maintain indoor temperature in the possibility of power cuts. With a need to move towards more and more renewable energy sources, it is important that we anticipate the potential issues that could arise and plan around them. Lloyd highlighted a potential to connect up car batteries to houses in order to utilise each of our resources to the max.
“The thing about this new world we’re getting into where we’re relying on renewables for everything is that renewables are intermittent… We have to design our houses to be really, really efficient so that if the heat goes off for an hour, and the hot water heater goes off, you don’t notice it.”
Cultural shifts can cause a ripple effect that increases our carbon emissions
Lloyd uses the example of the hamburger as a cultural ripple effect. The rise of fast food and drive thrus has created a culture around eating inside our cars. As a result car manufacturers began to add in features such as tray tables and cup holders to make this experience easier for the consumer. As years go by, these features increase and the overall size of cars increase too as a response to the amount of time we are spending in them. All of these increases go far beyond sufficiency and enter the world of excess, where every extra feature and every extra inch of space is adding to the upfront carbon of the car. This is a great example of how our cultural and consumerist influences cause these ripple effects that amplify our impact on the climate at every stage.
Copyright Looney Tunes
‘Visualising’ the carbon may help us grasp its impact
Lloyd spent a long time deciding on the best metric of measuring upfront carbon and eventually settled on Wile E. Coyote’s biggest threat, an anvil. It can be difficult to grasp the real impact of upfront carbon when it is measured in pounds or kilograms. Therefore being able to say that the production of a Macbook Air took an anvil and a half of carbon or that a watch was half an anvil can be a really valuable image to help people understand the true impacts of their possessions.
Could a ‘carbon allowance’ be the answer to sufficiency?
Lloyd suggests that carbon rationing could be a good strategy to help reduce carbon emissions. Everyone would be allowed the same, whether that’s by year or by lifetime, and from there they are free to decide what to spend their allowance on. The idea is that the consumer would be encouraged to reflect on the impacts of the products they buy and the choices they make.
“So if you’re building lower cost housing, you could maybe say slightly lower standard because it’s small. But if someone wants to build 500 square metres and has the same carbon allowance, they’re going to have to really be careful and they’re going to have to build it to a really high standard. And then if you start saying oh, by the way, you’re only allowed to have this much carbon allowance to build your whole house. Well, then they’re suddenly going to be looking at saying the only way I can build my mansion is if I build it out of straw and hemp on woodpile foundations.”
Sufficiency, sufficiency, sufficiency: how much do you really need?
“In this new world of upfront carbon, we have to turn that on its head and start thinking about sufficiency. How much do we need? And this goes through everything. How much clothing do I need? How much food should I be buying? How big is my car? Do I need a car? How big is my house? Everything we do we should look at it. And I often say when you look at the world through the lens of upfront carbon, everything changes. You just start thinking differently about everything you do and everything you buy.”
Tilmann Kramolisch from natureplus explains why their eco label was established, how materials and products are assessed, and what it means to use a natureplus certified product on your project.
Interview with Tilmann Kramolisch
Tilmann Kramolisch is the Managing Director at natureplus, a non profit eco label that aims to provide transparency and clarity to the consumer within the construction sector. The natureplus accreditation measures the impact of different building products on the environment and human health, to ensure that any product with a natureplus label is certified as healthy and sustainable. In this chat, Tilmann talks us through the natureplus accreditation process as well as highlighting some key differences to be aware of in other eco labels.
Healthy building products don’t harm the natural world or human health
The natureplus eco label certifies that building products are not harmful to the environment or human health. The World Health Organisation (WTO) has classified a condition called sick building syndrome, which refers to the negative impacts that a building can have on an occupant’s health. Leading causes of sick building syndrome are damp/mould issues, poor ventilation and toxic emissions from materials or the environment. Many natural building materials are proven to tackle these issues and by reducing the use of harmful chemicals/pollutants, the environmental and human health risks are significantly lower.
Materials are not the same as building products
Tilmann makes a key distinction between building materials and building products. Materials refer to a substance that can be made into many different things depending on how it is treated or used, whereas a building product refers to one of the outputs. Tilmann uses clay as an example of a building material, that can be used to make the building products of plaster or bricks. Natureplus measure the sustainability of building products on the market.
The natureplus eco label takes a holistic approach
Tilmann explains that the natureplus certification rests on three core pillars:
Health
Climate protection
Sustainable resourcing
For a product to be classed as a healthy product and receive natureplus accreditation, it must consider all three of these in all aspects of its usage and existence.
Asbestos is a good example of a product that would have failed the natureplus accreditation. It was originally considered a great material with many positive attributes. However, we now know how harmful it is to our health and when a building is deconstructed this material must be carefully removed and disposed of. This therefore negates the previous intention of saving resources as it cannot be reused. So if you begin with the three pillars approach when creating a new building product, you are mitigating any of these risks before it is widely available for use.
“When you develop a material or plant material, it’s very important that you apply all three. So healthy accommodation, climate protection and sustainable resourcing.”
A supply of cork
Golden rule: When it comes to fossil fuels, leave it in the ground
The natureplus label requires a product to be composed of at least 85% bio-based mineral materials or recycled materials. This is to exclude products that are primarily petrochemical based and ensures that the products aren’t damaging the environment or human health.
The process utilises independent testing to ensure transparency and quality
The Nature Plus Association (NPA) is the non-profit responsible for issuing the eco label. However, the assessment of the building product is carried out by a cooperative called the Nature Plus Institute (NPI). So the NPA sets the criteria and the actual testing is undertaken by the NPI.
Tilmann recommends taking a closer look at which companies are issuing eco labels and check the transparency of their process. In the case of natureplus, the assessment is carried out by an independent body to ensure transparency and quality assurance.
To test the climate impact of a product, a lifecycle assessment is performed. This looks at the A1, A2 and A3 stages of the building product, which refers to the upfront carbon emissions: from cradle to gate.
When it comes to assessing the health impacts of a building product, there are two areas that need to be assessed: what material does the product contain and what comes out of the product? For example, the Eco Institute in Cologne will test the product for substances such as formaldehyde or Volatile Organic Compounds (VOCs). They will then put a sample into an airtight chamber and measure the emissions from the product over a 28 day period. In order to meet the natureplus standards, the product must not exceed very strict thresholds.
Quality control is assured through the natureplus guidelines
natureplus have strict testing standards which are replicated in a variety of different laboratories and testing sites. By having set standards and a precise criteria, the results can be guaranteed to be accurate and consistent.
An Environmental Product Declaration (EPD) does not necessarily mean it is sustainable
Unlike the natureplus eco label, an Environmental Product Declaration (EPD) just quantifies the environmental impact of a product and does not indicate whether these are positive or negative. The label in itself is therefore not a signifier of quality or sustainability and instead offers transparency. This is very much needed in the construction industry but does require further research to determine if the product is good or bad. The natureplus eco label instead tries to communicate quickly and clearly that this is a product you can trust to have a focus on health, climate protection and sustainable resourcing.
“Communication is key and what we try to do is do it as simple as possible. So this is why we do this very, very big testing that we then put into one simple statement: this product is natureplus. So it’s really to make the complex communication as simple as possible.”
The natureplus eco label is a good indicator that a company has strong core values
Manufacturers must collaborate in the accreditation process by providing key information about performance, composition, etc. It also costs around 8000 euros to receive the label as well as an annual licence fee. The natureplus eco label is therefore a really good indicator of a sustainable product as in addition to the quality assurance, you also know the company has put in time and resources to achieve it.
There are three primary types of labels out there and it is important to understand them
Eco labels like natureplus, assess a product on the level of sustainability and should provide some tangible information about its impact and composition. The second type of labels are labels run by the manufacturers themselves. These labels will highlight some information about the product sustainability but they do the criteria development and assessment internally, which reduces transparency and lessens accountability. The third type of label refers to labels such as EPDs. As mentioned earlier, these are merely a declaration and it doesn’t say that this product really is environmental friendly or not. It is key to understand what each label means as each process has a different implication on the meaning of the label.
“A very harmful product actually could get an EPD. It’s good that they do because at least they are transparent with the information, but yeah, it’s not an eco friendly product necessarily.”
The Natureplus eco label is primarily based in Central Europe
Tilmann explains that natureplus is an international label and certified products are widely available, but the majority of the products are produced within Centural European countries. Sadly, there are no UK manufacturers with a natureplus eco label yet but there is hope for the future.
Exchanging ideas is crucial in the sustainable building sector
natureplus is a European network and in the face of the climate crisis, it is crucial that we are taking inspiration from countries with innovative ideas. Tilmann explains that we can turn to the architecture of Turkey to understand how to using shading to combat overheating or to the Netherlands where an innovative, pre-produced facade that can be assembled within days has proven to be popular. By tuning into the different solutions from European countries we can pool our collective knowledge to tackle many of the challenges that face us.
“Think global, act local”
The ultimate goal is to have enough natureplus products that you could build an entire house out of them
Tilmann explains that at present natureplus has certified approximately 600 different building products, from insulation to CLT timber.
There is a list on the website of all of these products. However, if you need to gather some more information about performance, some useful databases to use along side the natureplus product list are 2050s Materials, First Planit Materials and Powerbook.
Ben Adam-Smith caught up with various people who were involved with the Passivhaus workshop event and asked them for a piece of advice that could be applied to a Passivhaus project. These tips are in no particular order.
1. Put ‘Passivhaus standard’ on the brief on day one
Anna Carton from Passivhaus Homes recommends integrating the Passivhaus standard as early as possible into your build, preferably pre planning. Passivhaus is a holistic approach and all aspects of the design influence the performance of your home. Anna suggests that it is possible to take a standard design and make it into a Passivhaus design, but warns that aesthetic choices or use of certain materials, etc. might introduce challenges around thermal performance. Therefore, starting with clear intentions from the beginning can lower your costs and save you the headache.
To find out more about Passivhaus Homes, head over to episode HPH341, where Jae Cotterell debates whether embodied carbon or energy efficiency should be our priority.
2. Consider the placement of your services early on
Gordon Bunker, owner of Worcester Renewables, recommends taking some time to work out where best to locate your ventilation, heating and power generation systems. Gordon explains that building services can be overlooked in the design stages or assumed to be smaller than they are, so proper consideration early on will ensure they are allocated enough space and therefore easily accessible for maintenance. Gordon mentions that 3-5% of your total floor space should be put aside to house these systems.
Join The Hub to access our in-depth video case study of the Kinver retrofit.
3. Budget for thorough airtightness testing
Neil Turner, the UK Technical Manager for Ecological Building Systems, highlights the importance of intermediate airtightness testing during a Passivhaus build. Neil suggests undertaking an airtightness test once all of your membranes, tapes and boards are in place to identify if you have missed any areas around windows, doors or pipes. If there are some leaks, address them and test again to make sure the airtightness has improved. Then you can start on your finishes. Doing this will ensure that you seal up any leaks at a point where they are still easy to fix.
Rob Bohm, Head of Energy and Sustainability at CLPM, explains that Passivhaus principles will impact the design of your house so you must be prepared to fully commit. Rob says that Passivhaus projects are “not for the faint hearted and can have severe limitations on what your choices may be”, but if you undertake the journey it will repay you in numerous health, lifestyle and financial benefits.
5. Keep it simple
Mike Shufflebotham from 21 degrees highlights that when it comes to high performance windows and doors the simpler the design, the less it will cost and the better it will perform. This is because the glass is a much better insulator than the frame. By introducing mullions and transoms into your window design, you increase the proportion of frame to glass, which as a result lowers the performance, whilst increasing the cost through the additional labour and joinery. The final product performs worse and costs more than the original simple version.
Embracing simplicity is a common theme in Passivhaus building. We explain why in episode HPH350.
6. Take a fabric first approach
Robin Miller, Director of Beco Wallform, explains that “if you get the right fabric, the right quality and the right performance, it makes the rest of the project so much easier”. Through the fabric, you can minimise the energy requirements of your home and create a much more comfortable living environment. Robin therefore recommends taking some time to identify which building material aligns with your self build values and overall goals for your home.
7. Optimise the form (or shape) of your home
Alan Budden, Architect and Passivhaus Designer from Eco Design Consultants, advises keeping the overall shape of your house as simple as possible (achieving a good form factor). By doing this, you minimise the heat loss area relative to the floor area, making it perform better and also enabling you to reduce the amount of insulation you need to meet Passivhaus (which in turn makes it cheaper!). This doesn’t mean that the building has to be boring, in fact many classic architectural styles use simple shapes and get the proportions right. The structure is also a blank canvas and you still have the freedom to be creative with materials and internal finishes.
8. Check your window frames for insulation
When it comes to high performance components, Vasilis Giannopoulos from Internorm highlights the importance of checking that your window frames are well insulated. For example, if you choose composite windows identify whether there is insulation in between the external and internal layers, rather than just an air gap.
“When you go into the market for Passivhaus windows, always focus on the frame of the windows. It’s going to be easy for any window supplier to match the performance specifications you have for the glazing units. So please focus on the quality and the performance of the frame.”
9. Make sure you research your future ventilation system thoroughly
Ben Collins from Air Flow suggests researching the ins and outs of your ventilation system at the planning stage. From talking to installers to identifying which add ons you may require, you will be able to get a clearer picture of which ventilation system may work best for your future home and offer you the best energy efficiency. There are many bolt on options out there that offer different features and benefits, but they must be brought in and designed during those early stages.
10. Understand your budget
Iga Panczyna, Architect and Passivhaus Designer for Allan Corfield Architects, believes that it is crucial that self-builders have a realistic understanding of what they can achieve with their budget. Iga highlights that there are ways to achieve a Passivhaus on a restricted budget, but this relies upon good design and clear planning from the start. Additionally, those whose budgets will not quite get them to Passivhaus standard, can still follow the principles to get the home as close as possible.
11. Practice any skills you intend to use during your build
Paul Jennings from Aldas recommends practising your skills ahead of when you will need them for your own build. This is particularly important for insulation and airtightness because there needs to be attention to detail to ensure the finished performance.
“My top tip is plan ahead, prepare, practice, look at what you’re doing, think about the design, look for joined up-ness, is your airtightness line consistently joined up? Is it practical? If you’re doing any sorts of fancy tapes, you’re doing preformed corners, practice! Don’t practice on your build, practice before you get to your build.”
A few years ago we made a documentary with Paul Jennings
12. Don’t mess with the formula
The final tip from Ben was to not mess around with the tried and tested approach. It can be tempting to go off piste and just do the bits you like, but Passivhaus building is a holistic process and by messing around with one aspect there could be unintended consequences.
“That’s one reason why I like certification, because it shows that you’ve done all the bits and that it should work at the end of the process, because it’s a quality assurance process.”
Neighbours Wookey and Rob Leedham explain why they were motivated to retrofit their homes, how they built up knowledge and why engaging with others on a similar path has been extremely useful.
Interview with Wookey and Rob Leedham
Neighbours Wookey and Rob Leedham share their experiences on their individual retrofit journeys. With technical minds and a passion for problem solving, this pair of DIY retrofitters have undertaken a vast range of tasks, from installing external wall insulation (EWI) to building a ground source heat pump! In the process they have saved a lot of money but we look at why they were well suited to this DIY approach and the value that they have taken from networking with fellow retrofitters (through green building organisations such as the AECB).
Wookey’s retrofit
Wookey’s journey began when he and his wife bought a house in Cambridge that initially looked presentable and tidy. However, it was draughty and not particularly comfortable and soon they decided to retrofit it. Having hired builders in the past and not been completely satisfied with the standard of work, Wookey decided to undergo the renovations himself.
Wookey’s house before retrofittingWookey’s house after retrofitting
The existing dwelling is a 7 x 8 metre square, 1960s detached house with a separate garage. During their renovations they began by insulating the loft and replacing the front door. They then continued on to wall insulation, both internal and external in different parts of the house. This was followed by replacing the old and inefficient boiler, which is now also about to be upgraded to an air source heat pump and eventually replacing all of the windows. Furthermore, Wookey chose to build an extension that connected the house with the garage and added a sun room.
Extension beforeExtension designExtension After
As the existing house is masonry cavity wall construction Wookey decided to keep things simple and construct the extension in the same way. They did hire a builder to put up the superstructure but Wookey undertook all the internal work, fitted the underfloor heating, tested the airtightness and even learnt how to fit an air source heat pump.
This DIY approach has been time consuming, with it coming up to a decade of renovations. However, it has also allowed them to save a remarkable amount of money.
“I learned quite a lot from having done it mediocrely once [renovating his previous property] and going, right, this time we’re doing things properly.”
DIY allows you to control the quality of the work
DIY projects can be stigmatised as below a professional standard, but Wookey explains that DIY has enabled him to get a much better finished product. After some bad experiences with builders cutting corners, Wookey found that doing the job himself allowed him to get the standard he wanted and all the details correct.
In Wookey’s experience, the nature of the building industry means that the right way is considered to be the one that gets the job done in the fastest time.
“The real problem with tradespeople is that everything’s time based. How many hours is this going to take? So they won’t necessarily thread the plumbing or the wiring in the right place, they’ll do whatever they can get at in half an hour, rather than doing it properly which is literally going to take 10 times as long. I think that’s the main advantage of doing things yourself is you get those little details right.”
Having a long-term plan for your retrofit is essential
It is commonly recognised that an over-arching retrofit plan is very important to ensure a successful project, mainly because it will help to avoid having to retrace steps or undo your work. DIY retrofits can take a long time and if you choose to live at home during that time, it will likely happen bit by bit or one room at a time. For example, replacing your windows without considering how it links up with insulation may be a missed opportunity.
Addressing a thermal bridge at the front doorSolar PV
Modelling your home in PHPP is invaluable
Wookey also decided to do the energy modelling for his home himself. Initially he was reluctant to use PHPP but discovered that it was fairly straightforward and offered a lot of benefits. It is a great tool for retrofitters as it helps you plan your retrofit, predict the potential performance of your house and identify what is needed in order to reach a given outcome. Sarah Lewis from the Passivhaus Trust helped us break down the topic of PHPP, providing an in-depth explanation of the benefits and sharing her own experience on a retrofit journey.
“I put PHPP off for a long time, because it’s a pain in the arse and it took a month from a standing start, even though I kind of understand the principles. But you know, it’s just if you’ve not done it before, it’s hard. But then you realise, actually, we could get to EnerPHit or at least pretty close on this house.”
You will need a certain set of skills for a DIY retrofit
Wookey’s background is in software engineering and he has always been interested in fixing his own cars. This meant that shifting his mindset to building physics wasn’t too difficult. Wookey advises to anyone starting out on this journey to spend the time learning the processes and discovering the how and why. Wookey admits that it can be a bit difficult to find this information online, but the Denby Dale Passivhaus study is a great place to start as they provide clear examples of where techniques have worked. This is also why retrofit and self build communities such as Cambridge Carbon Footprint, Cosy Homes Oxfordshire and The Hub here at House Planning Help are amazing resources that allow you to ask questions and learn from experts or others who have already been through the process.
“I’ve got a fair amount of practical skill. I’ve always fixed my own cars and that was where it started… and electronics. Buildings are quite simple in comparison to cars and electronics! It’s often fairly basic stuff. It’s mostly a matter of understanding building physics.”
There is a shortage of green builders in the UK
Wookey explained that in the Cambridge area and many other parts of the UK there is a real shortage of tradespeople who are experienced in sustainable construction. Hopefully this will change over time as demand grows and the industry comes to understand the need for attention to detail. In the meantime this might be another reason why a DIY approach is preferable.
External Wall Insulation (EWI)Eaves insulation
Some areas are worth paying the professionals
Tiling and plastering were two areas where Wookey decided to bring in a professional because they both require a level of practiced skill in order to achieve a good quality outcome.
Wookey also paid £1500 for some drawings for his extension, but did end up regretting this as they designed a standard box that didn’t consider energy efficient principles. As a result, Wookey ended up drawing his own plans and only used the plot measurements from the initial drawings to aid his own design. This offered him the freedom to create exactly what he wanted, however there is an added pressure to this and if things are calculated wrong then that is your responsibility.
“Generally, my assumption is that I can do everything, and it turns out that’s true for everything… apart from plastering, that’s the hardest thing in the world.”
DIY retrofits can be all consuming, it is important to maintain a balance
A DIY retrofit can be a long and time consuming process. For Wookey, the challenges and puzzles are enjoyable, but they can become all consuming if you are not careful. Wookey and his wife decided early on that at least one weekend a month they would do something other than DIY to ensure that they maintained a good balance. Wookey also highlighted that it was easier to give so much attention to their retrofit as they don’t have children and the commitments that come with family life.
Guy Hargreaves employed a contractor to carry out his retrofit. Watch our in-depth video case study in The Hub.
Many people are interested in retrofit but not the DIY approach
Since undergoing his own retrofit Wookey has encouraged family, friends and colleagues to consider taking on their own projects. While they understand the potential benefits a retrofit can deliver they do not always warm to the DIY approach! So, you can of course bring in a contractor to do the work.
DIY retrofits are a great option for people who have a passion for doing the manual work, enjoy learning and have plenty of time available.
“A surprisingly large fraction of the people I meet, think, yes, that is a good idea and I should definitely find out about it, a very small fraction of them want to do it as DIY or take ownership, they don’t really want to learn about the whole thing. They just want somebody to do it and there’s a terrible shortage. There aren’t enough people around here at the moment. I know several people who’ve been quite keen, and have tried to get quotes and struggled or been told that we can come and get to you in two and a half years time.”
You will begin to notice the benefits
Wookey explained that as well as the obvious benefits of an energy-efficient house being cost effective and warmer, they also began to notice small things that improve their daily life. For example, when you achieve a good level of airtightness and have triple glazed windows it becomes more peaceful. Also dust mites disappear when the MVHR is running and keeping the home within an optimum humidity range.
“When you go and rent somewhere to stay, you go to these cold and draughty rented cottages. And you think it’s not like my nice house at home. So you get quite picky about buildings once you’ve tried living in one that’s actually good.”
Rob Leedham’s retrofit
Wookey’s neighbour Rob Leedham has also been gradually improving his home. Rob and his family have lived at this house for 23 years and although he had no grand plan at the beginning, he has been consistently adding one green measure after another.
Rob has undertaken the whole of his retrofit as a DIY journey, including installing 150mm of External Wall Insulation (EWI) on all external walls and insulating the footings of the house. Rob is also passionate about solar power and energy generation. 12 years ago they installed solar PV panels on the roof and have more recently hooked it up to an inverter that will be able to accommodate both additional solar panels and batteries for energy storage.
Community access to airtightness testing kits will help make the retrofitting process more affordable and more accessible
One of the trickiest parts of retrofit is reducing the air leakage of a property, which calls for a good airtightness strategy. Having the airtightness layers all in place is not enough – the airtightness needs to be checked and then further leaks can be identified and addressed.
Rob showed Ben two fans that can be used for testing. One is a professional blower door kit and the other is a homemade version. These can loaned to other retrofitters in the area. A standard airtightness test is time limited and will cost around £300. Rob’s hope is to get a few for their group in Cambridge so that retrofitters can take their time to achieve the best airtightness results possible and not feel like they need to rush on.
Using their airtightness kit, here are the current findings for both Rob and Wookey:
Wookey had aimed for below 1 air change per hour (at 50 Pa) and is currently measuring at 1.52.
Rob had aimed to get his below 3 air changes per hour and is currently measuring a 2.1.
Rob’s DIY blower door kit!
Rob built his own ground source heat pump
Rob is also technically minded and opted to build his own ground source heat pump from scratch.
“The thing about ground source heat pumps is that they are actually very simple. There’s a compressor or an expander, and a pump and two heat exchangers. That’s basically it. So it’s not that hard to build your own. Some parts of it are inside and some parts outside. And so the electronics is inside and the header tank. And there’s a little display there that says it’s got a coefficient of performance of 4.4 at the moment. So inside, we’ve got that part that calculates the efficiency. And there’s a little electric meter, a standard electric meter for measuring how much electricity is used. It’s been going for about two years and a couple of months, and it’s up to four megawatt hours of electricity in to provide all of the heating and hot water for those two and a bit years.”
The key to heat pumps working efficiently is a well insulated house that doesn’t need much heat.
Rob does not recommend this route however unless you really enjoy the process and recognises that the sensible choice is to buy one and have it installed by a professional!
Stuart Dyer’s retrofit
Stuart Dyer is another member of the Cambridge retrofit community and has been retrofitting a 1930’s detached property. Stuart took a different approach and moved out for a year whilst they carried out an extensive retrofit. The process included external wall insulation, triple glazing, fitting mechanical ventilation with heat recovery (MVHR) and installing an air source heat pump. Stuart highlights that one of their biggest challenges was get their airtightness to a good standard and they worked quite hard on this area. They also put in underfloor heating, which works well with the air source heat pump, and insulated quite a lot under the floors.
Stuart likes being in Cambridge because there is quite an active retrofit scene, consisting of monthly meet-ups of the Association for Environment Conscious Building (AECB) (that Wookey organises). This offers a great chance to meet with people in the pub, discuss with those who have already done a lot of work, the good things to do and the pitfalls to avoid. Transition Energy Group is also quite active in terms of new technologies, new interests, and there is a lot of good advice there. Cambridge Carbon Footprint have lots of great case studies and also runs an Open Eco Homes each year where you can visit other people’s houses, whether they are new build Passivhaus or up to EnerPHit standard.
Search for ‘green building’ meet-ups in your area
In every town or city there will be opportunities to network with like-minded individuals and professionals by tapping into local green building groups. These are often as much about inspiration as sharing knowledge but it’s particularly useful for those on a DIY journey who may encounter challenges and be looking for advice or contacts.
Linda Farrow from Agile Homes explains how their prefabricated panelised system can deliver high quality and truly affordable homes that are good for the planet.
Interview with Linda Farrow
Linda Farrow and her partner Craig White set up Agile Homes in 2019 to address the need for better housing in the UK. They aim to deliver low-cost homes without sacrificing on quality, and each of their buildings is low carbon, energy efficient and has the ability to be disassembled easily (at the end of its life cycle).
Timber panels with straw in-fill are made off site
Linda explains that at the core of an Agile Home is their Modern Methods of Construction (MMC) panelised system. These panels are prefabricated in a factory and then assembled quickly on site, giving you a watertight structure within a day or two. The use of natural materials like timber and straw ensures that the homes have an extremely low embodied carbon and the panelised nature of the system mean it can be easily customised to meet the client’s needs. This makes it incredibly versatile and can be used for a variety of projects, from a block of flats to a one bedroom bungalow.
Their housing model aims to overcome common challenges
Linda explains that as part of their mission to make good quality and affordable housing accessible in the UK, they needed to identify the current barriers in the construction industry and come up with creative solutions to overcome them.
There is a cultural wariness of adopting renewable materials
England has a romance with brick and block construction that is proving tricky to shift. Even our children’s stories have perpetuated this message by telling us that a house made out of brick will be sturdy whereas a house built from straw and sticks will leave us vulnerable to attack.
This cultural mindset shift will take time to change but as more projects are completed it will keep demonstrating how well natural materials can work.
There is a lack of affordable land to develop
The price of land is currently a major barrier for affordable housing projects and often takes up a large proportion of the budget.
By collaborating with councils, housing associations and charities, Agile Homes works to unlock land at low or no cost for social value. This can quickly reduce the delivery cost by around a third.
It needs to be easier to finance and insure sustainable projects
It can still be a challenge to finance or insure ecological projects because they are deemed higher risk.
So Agile Homes has invested time in developing relationships with companies such as the Ecology Building Society and they are now an approved supplier.
They also gained BOPAS (Build Off-site Property Assurance Scheme) accreditation which is recognised by mortgage lenders as providing the necessary assurance that properties that use modern methods of construction (MMC) will be readily mortgageable for a minimum of 60 years.
Gaining planning consent is not always straightforward
Getting planning permission for a project can be quite involved and take time, which is why Agile Homes have developed a modular solution called TAM which complies with the Caravan Act. This generally means planning permission will not be required because they are moveable rather than permanent structures.
TAM (Transportable Accommodation Module) is a rapid response housing solution
TAM is a prefabricated, rapid-response housing solution.
The modules can be transported ‘flatpack’ to site and assembled quickly, leaving you with a watertight shell in a day or two and operational within a few weeks. Depending on the site and the needs of the client, TAM can also be umbilical to an existing building, using the same power, water and drainage systems without the need for planning permission.
“We’re not quite there yet, but one of our aims is to make it as easy for individuals and community led organisations to buy into our system as if they were going to a car showroom, and they can sign the finance agreement and drive away in their car. So in the same vein, they could sign a finance agreement and have their TAM delivered to their site”
Delivering a ‘turnkey’ solution helps to maintain quality
The larger the development the more likely it is that different companies and sub-contractors will be delivering different aspects. Inevitably this can lead to mistakes or inconsistencies. So at Agile Homes, where possible, they like to control the whole process.
“In essence it’s about control, and making sure that we can deliver the quality of product to the client. If you use a conventional procurement method where you’ve got the design and then you transfer over to a main contractor, the main contractor is incentivised to find all manner of ways to reduce their costs and increase their margin. And that’s not a criticism, that’s just the way the system is set up. We are a values led organisation and our board scrutinises everything that we do carefully. So I think it is about aligning everything that we do with our core value of respect for people and planet. It’s about control throughout the process to make sure that we can deliver to that time after time for our clients.”
Prefabrication can take place at a ‘pop-up’ factory
The panelised system has been designed so that it can be put together with high end power tools. In certain circumstances – such as at the request of a community led project – they can bring the manufacturing closer to site and create a pop-up factory in empty barns or industrial units. This has the added benefit of upskilling communities who are interested in sustainable building.
The Agile team
The best collaborators have respect for people and planet
“The ideal client would be someone whose values align with ours, so respect for people and planet, someone who has access to substantial amounts of patient capital, who is like us, genuinely interested in providing as many people as possible with homes that are affordable in perpetuity. Because having an affordable home, a safe civil space to be in is the foundation stone, in our view, for sustainable regenerative communities. And climate change is quite rapidly going to be a question of water and food crisis. So there are many, many immense challenges on the horizon for society. We want someone who, like us is very focused on helping society to put in place the foundation stone for us to then have the capacity to deal constructively with all the challenges that are yet to come.”
Inter-governmental policy is needed to be able to deliver widespread affordable housing
Linda explains that the biggest challenge for Agile Homes is access to patient capital and limitations caused by a lack of inter-governmental collaboration on housing policy.
“Governments have a duty in between terms and outside of party political allegiances to look after human beings and the planet. There are some policies that should be negotiated and agreed as being inter governmental.”
The natural materials contribute to a calm environment
Agile Homes has carried out work for local authorities, housing associations and charities, and quite a lot of their residents are vulnerable. This can range from physical disabilities, mental health issues to learning disabilities. So some key feedback they have received is that the natural materials and quality design have created a calm atmosphere which can be of great comfort to anyone but particularly to those with special needs or mental health challenges.
Agile Homes are committed to sustainability from their build system to their business model
Linda explains that Agile Homes aims to create a business model for affordable housing by looking at a wide range of resources which promote sustainability and social value:
The Agile Homes team is also in the process of finalising their Carbon and Social Value Tokens, which will allow people to offset their carbon emissions in local, sustainable, social developments.
“We’ve been thinking a lot about how to we evidence and generate revenue from the carbon storage that we’re achieving in our buildings and also in the social value that we’re creating. So we’ve been doing work behind the scenes to build calculators and we’re just about to go live with what we call carbon and social value tokens that can potentially be traded. What that means is that we have found clients who are interested in actually buying and paying for the stored carbon and the generated social value as part of their ESG governance systems and processes. So rather than offsetting their carbon footprint by paying for X 1000 trees, in a plantation 1000s of miles away, they’re choosing to buy the carbon that we can evidence is being stored for a minimum 60 year design life in our buildings and I think that’s very exciting. We have plans to use that methodology to generate revenue that can then further reduce the costs of some of our schemes for our most vulnerable clients. We’re really excited about that extension to the model and that rethinking of how do we generate value and revenue in a truly regenerative economy?”
Meredith Bowles from Mole Architects shares his experience working with timber as a construction material and explains the benefits and drawbacks of the different build approaches.
Interview with Meredith Bowles
Meredith Bowles, Founder and Director of Mole Architects, shares the pros and cons of different timber construction methods. Initially working on additions and conversions of Victorian building stock in London he found the masonry cavity wall approach unsatisfying, messy and difficult. So shifting towards timber construction was transformational. Meredith undertook his own self build project in 2002 and created a sustainable timber home that is still ahead of the government green guidance 20 years later. In this chat, Meredith sheds some light on timber build approaches including stick build, oak frame, CLT (Cross Laminated Timber), SIPs (Structural Insulated Panels), prefabrication and more.
Stackyard in Suffolk
Back to basics – What is timber?
Timber is wood that is prepared for use in building and carpentry, and if you visit a builders’ merchant in Britain this usually refers to white wood which is most likely to be Scandinavian, Lithuanian, or Russian softwood. In timber construction, this is most commonly assembled into stud walls which are sheathed and filled with insulation.
Although the UK has a medieval history of timber construction using large oak framing, the North American approach of using timber stud walls is still not as common as brick and block.
Over the last 20 years, engineered timber has been rising in popularity and involves binding or fixing fibres, strands, veneers, etc. into composite products to increase the strength and efficiency. Plywood is the simplest version of this, but CLT, LVL and glulam are also common.
With the wide range of timber products and construction methods available, timber is a fast growing sector of the construction industry in the UK and an obvious choice as we look to build more sustainably.
Alde Valley Barn ‘stick build’
Qualities of timber
Timber is a sustainable material with low embodied carbon impact
Timber is a renewable resource with low embodied carbon that can be engineered in a wide variety of ways to produce different results. Although timber in itself is sustainable, Meredith stresses that we must try to reduce our consumption of it and use it as efficiently as possible.
“Some advocates of timber make a claim that the growth of timber absorbs CO₂, and therefore, using more timber is a good thing. It’s a perverse kind of argument. If we are going to scale up timber construction throughout the world in order to try and minimise the use of more carbon intensive construction methods, then there’s going to be such an enormous demand on the available construction timbers. Surely it’s better to make it more widespread but to engineer the use of it, so that you are using less of it. I can’t square myself the argument that using more of anything is a good thing.”
Timber frames are better suited to accommodate insulation
Not only is timber a regenerative resource which during its lifetime will help with carbon capture and biodiversity, it also offers a logical way to better insulate our homes. Meredith explains how:
“There are a number aspects of sustainability, the primary one is cutting down our fossil fuel use and carbon emissions, which is what has been fuelling climate change. To do that, we need more insulation and if you’ve got a timber frame building, you’ve got a lot of space in it that you can fill up with insulation. It’s a really easy way of making a really well insulated building, because you’re building it out of stuff with a lot of space. The alternative masonry construction requires you to build two leaves with a really big gap in between to fit the right amount of insulation in, which becomes quite cumbersome and complicated.”
Timber can be utilised as a design feature or entirely hidden
Timber construction allows for more versatility and freedom with your design. Depending on how it is used, timber stud walls can be hidden, as it is sheathed on both sides, or incorporated into the design of the house through exposed beams or entire walls.
Timber is a warm material
Wood offers both an emotional and physical warmth that people respond to. The visual honey tones create a warm and soft interior but there is also a literal warmth in the sense that it has insulative properties. When you feel a masonry surface it absorbs the heat from your skin quickly and feels cold to the touch, whereas, timber doesn’t transfer the heat as well and feels warm.
Securing finance and insurance for a timber build can still be a challenge
Insurance companies and lenders still seem to view timber as non-traditional and therefore as a higher risk. Meredith highlights that these types of entrenched views are rarely as a result of statistical analysis and instead are built on a societal conception. As mentioned before on the podcast, the fairy tale of the little pigs has ingrained a sense of safety in brick-built housing and a sense of insecurity in one made of sticks, despite all of the evidence that suggests otherwise. As a result of this, there are more obstacles to overcome during timber construction which is stopping it being embraced by the mainstream.
“People say, ‘Well, I can’t get a mortgage for timber frame building’. Of course you can, but it’s not the norm, and therefore it’s slightly harder. Plus, I suppose if you go to any old builder down the road, and say, can you build a house, then they say ‘Oh, yes, we can build out a brick and block’ and they wouldn’t know where they’re going with timber. So it’s a whole industry which needs to change or is changing.”
Fire testing timber products
Fire risks are a common concern, but often exaggerated
The GLC (Greater London Council) has banned the use of timber in any external walls, because of the fallout from the Grenfell tragedy. Grenfell had no timber in the construction, and that was not the cause of the fire, but there’s been increased concern and cautiousness over anything that may be a problem in terms of fire as a consequence.
Timber needs to approached in a similar way to steel in order to resist fire damage
We all know that wood burns, but the reality of timber construction is that the timber frame is covered up, usually with plasterboard. Similar to our understanding of steel in construction, plasterboard is one of the best ways to stop fire reaching the material behind it and by encasing the structure, the heat is not going to reach the timber for some time. Incidentally, Meredith highlights that testing has shown timber to out-perform steel in the case that fire breaks through this barrier. As a result steel actually deforms, bends and can lead to structural failure much quicker than timber does.
Meredith recognises that much more research needs to be carried out in relation to fires, but does highlight that the government could be taking similar steps as Germany and Scandinavia by bringing timber into the same legislative framework that steel currently is in.
Knowing the charring factor of your timber can reduce the chance of structural damage during a fire
The charring factor in timber is another important consideration when it comes to the fire safety of timber framed houses. This refers to the amount of time it takes for the surface of the timber to char and lose its structural properties and how much of the surface is affected. As a result of this testing, timber used in construction has been oversized in order to compensate for the timber that would be lost during a fire so that it remains structurally safe.
The Black House
Meredith’s House
Meredith built his house in 2002 and got inspiration from projects in North America and Scandinavia, which had to deal with the harsher climate. The house consists of a prefabricated timber frame which was insulated using recycled newsprint/cellulose. Meredith’s home is in The Fens and it is common for building foundations to be piled with a concrete ring beam and a beam and block floor. However, to reduce the embodied carbon of his home, Meredith chose to use glulam timbers to create a ring beam above the ground, avoiding contact with water, keeping the structure well ventilated and dry. The finished house was even fitted with an air source heat pump, MVHR and solar canopies to help mitigate overheating.
The glulam timber ring beam
Construction of The Black House
When the Future Home legislation comes into force, the government guidance will have finally caught up with Meredith and his millennium home… just 20 odd years later.
Stick build is the most straightforward method for timber construction.
Stick build is when individual timber elements are cut and combined on site to form the structure. It is often sheathed by plywood or OSB to create a cavity for insulation.
‘Stick building’ at Riverview
Completed home – Riverview
Join The Hub to access the in-depth video case study of this timber build in Buckinghamshire
Moisture must be carefully managed in a timber structure
Materials like rockwool or glass fibre insulations are water resistant, which means any build-up of condensation in the wall cavity won’t be absorbed by the insulating material. This means that any moisture will run down the material and begin to pool at the bottom, slowly rotting the plate at the base and causing unseen damage that you won’t discover until it is too late. Meredith highlights that natural insulating materials such as cellulose, recycled newspaper, wood fibre or wool all have the ability to absorb moisture and then pass it out again. This means they take it in during the winter months and release it in the summer, helping to keep the timber structure itself dry and in good condition.
“Building physics has finally been properly understood and we put the layers with a greater resistance to moisture on the inside, and layers with a less resistance on the outside.”
Natural insulations are often not as effective as petrochemical insulations
When comparing the insulative properties of natural and petrochemical insulations, natural materials often don’t perform as well and therefore more is needed to reach the required insulation value. In projects where space and budgets are tight, this can be challenging.
“PIR foam is about twice as effective as any of the natural insulants, so you only need half the space and often when you’re trying to figure out how to fit everything in, that feels like it’s a much better solution. But of course, those insulants don’t absorb any moisture, so the way in which the building needs to be detailed suddenly has to change. We tend to use both forms of insulation in different circumstances because there are benefits sometimes of using a PIR that can get wet without losing its insulation capacity. The building physics of it are quite complicated, and it is necessary to get to grips with that to know how to use one insulation over another.”
Cross Laminated Timber (CLT) is generally used for larger projects
CLT is a form of engineered timber which is created by gluing together at least three layers of solid lumber. The layers are oriented perpendicular to the last, helping to increase the structural rigidity. The configuration of CLT differs from glulam beams in which the laminations are all orientated the same way.
Cavendish Avenue CLT construction
Completed home – Cavendish Avenue
CLT allows you to create a really strong structure whilst retaining the sustainability credentials of standard timber. However, Meredith says that for small scale, self-build projects, this building material is often not needed and would result in using more timber than necessary. There are cases where Meredith has used this material in private residences, but it was often to support the complex geometry of a design, so it is best to assess on a case by case basis. CLT is often best suited for large projects, such as public spaces, schools, etc and is a great alternative for steel beams.
Dune House – CLT
Structural Insulated Panels (SIPs) offer many structural benefits but tend to rely on petrochemical insulation
SIPs are quite broadly defined but Meredith describes them as “a sandwich construction of plywood or OSB on the outside faces, which are glued together with a polyurethane foam insulation, a bit like those ice cream with a wafer on each side.”
SIPs have amazing structural properties and it can be very easy to produce a highly insulated, airtight building using them. SIPs are incredibly lightweight so are easily transported, can be put together quickly, and will reduce your foundation costs.
However, Meredith has concerns about using SIPs in his projects as they require the use of fossil fuels to create and have a potential to release harmful gas from the insulation material and formaldehyde in the glues on either side of the sandwich.
Brettstapel solid timber construction avoids use of glues
Perhaps a less common timber build approach is Brettstapel. This is a simple construction method that allows you to create solid timber walls without the use of fixings or glues. Layers of timber are connected with wooden dowels instead of being glued together, which makes it strong. Meredith believes that, similarly to the use of CLTs in self build construction projects, Brettstapel is not the most efficient use of wood on the market, but the prospect of creating a structurally strong material without the use of fixings or glue is interesting.
Timber cassettes arrive on site
Prefabrication can improve quality control, airtightness and speed up on site construction
MMC (Modern Methods of Construction) refer to the prefabrication of buildings off site before on site assembly. This has the potential to greatly improve quality as the work is carried out in a controlled environment with the right tools on hand and properly trained staff which should lead to a more consistent output. Prefabrication also can include integrated services and windows, and much of the airtightness detailing.
As a result, prefabrication can offer a fast assembly on site, as the majority of work has been completed in a factory. This also minimises the chances of any delays due to adverse weather conditions.
“We’ve all heard the stories, my house was built in five days. Of course, we all know that’s not true, the prefabricated timber frame went up in five days, it’s probably been two months of doing the groundwork before, then it’s another nine months to finish the job. But nevertheless, it’s a very quick way of getting a watertight building and stick built but prefabricated cassettes is the next level up.”
Timber panel lifted into position
The benefits of MMC rely on good quality control practices being in place
Meredith highlights that the outcome of your build is heavily reliant on who is building it, and whilst prefabrication has the ability to increase quality control, it still relies on people to be implementing and performing the necessary checks.
“There’s no reason why a really low tech way of constructing something can’t be as effective and give you as good a quality as someone who’s using a much more automated system. I’ve visited various kinds of factories and our clients have received big consignments of prefabricated timber panels that have been simply incorrect because the quality control wasn’t there, irrespective of the fact that they have all of the machinery so they should be able to make it work. And conversely, we’ve worked with small contractors who are building it in a shed using a jig, two blokes and a tape measure, and it’s gone together perfectly. So, I don’t think there’s one way that definitely works and another way that doesn’t. I think different companies have different reputations and that’s how you should determine it. Talk to people who have used their products before, don’t just look at the fancy machinery and think that that’s got to be better.”
Development with TOWN
Solid oak frames might be beautiful but are not the best use of timber
Meredith is measured in his approach to construction, meaning that every project must be considered on an individual basis and no construction method is entirely off the table. However, he does raise some concerns with solid oak frames in modern construction.
Within the self-build world there is an attractiveness of a contemporary oak framed home, as it is what we see in the traditional vernacular of our buildings. However, with the developments in construction and a focus on sustainability and insulation, large oak framing for small projects is a very inefficient and unnecessary construction method. This is because once you have fitted the stud walls between the oak beams for your insulation, the stud walls could actually hold the structure on their own, making the beams a very large, beautiful but unnecessary feature. In larger buildings, the oak beams may be of more use to the structure.
“We talked earlier about the idea of minimising your use of materials and the idea of engineering something which is efficient is part of sustainable design, not overusing things. So there’s a slight illogic of using oak frame in a contemporary domestic building”
Meredith avoids using tropical hardwoods due to their link to deforestation in the rainforests
When buying timber look for FSC (Forest Stewardship Council) or PEFC (Forest Stewardship Council) accreditation which Meredith believes are governed well.
However, some time ago Mole Architects did stop using tropical hardwoods due to the links to deforestation and logging in rainforests.
“I think even though there are supposedly chains of custody and forms of logging that are deemed to be sustainable, it seems like the destruction of rainforests is of a different order or a different scale of environmental problems to the cutting down of forestry land that is grown for timber from softwood. So, you have to make a decision as to what you choose to do in terms of environmental provenance of the product.”
Every project is different, so try and choose the best method for your build
“My ambition as an architect is to explore ideas and every project is different, every client’s different, and I don’t come with a predetermined idea about what I want to do. So for me, the excitement is each time, it’s an exploration of a new project and what’s going to come out of it. I think that’s the same with the structure and the construction. There are so many different ways you can do things, the idea that one is better over another I don’t think it’s true. You have to figure out what is right for your project.”
