Ben Adam-Smith explains why he plans to take on a new mission, and why that’ll mean a slight change of direction and more collaboration.
Ben and his family on their building plot in 2017
A new chapter begins
After 14 years and 400 episodes exploring what we should be building in the 21st Century, Ben Adam-Smith arrives at a natural turning point. The original question — what houses should we be building? — has, in his view, been answered. We know the ingredients: high-performance envelopes (Passivhaus standard), healthy materials, simplicity of form, walkable and biodiverse communities, and genuine involvement of occupants in the process. Rather than continue to revisit territory that has been thoroughly covered, Ben feels a niggling urge to do more with the knowledge, contacts, and credibility he has accumulated. The podcast has been his apprenticeship; now he wants to put that learning to work in actually delivering housing.
Ben’s home and wildflower meadow!
Why the shift, and why now
Tackling another self-build seems unlikely when Ben and his family still love their home and are quite settled. And continuing to make content for self-builders and those planning to retrofit after having closed The Hub membership could only be as a hobby. Therefore, with a new goal, it seems the right time to shift away from bespoke housing. More importantly, Ben has had this impulse to tackle a development before — he tried to pivot towards building just as the pandemic arrived, with a young family and not enough bandwidth to make it stick. The biggest lesson from that earlier attempt was that he cannot do it alone, nor would he want to. Collaboration, he says, is going to be central to whatever comes next.
Sally working on her own project
Introducing Sally Godber and Mike Roe
At the Futurebuild exhibition, Ben bumped into Sally Godber, a director at WARM, the well-known low-energy building consultancy, and a driving force behind the Coaction training initiative. What began as a casual catch-up quickly revealed a shared restlessness. Both felt they wanted to leverage their skills in a bigger, more hands-on way. Ben’s question — “Sally, do you want to build something?” — was met with an immediate and telling response: “I think I might.” That speed of reaction told Ben everything he needed to know about the potential. Mike Roe, also a director at WARM, joined the conversation, bringing deep technical expertise and a grounding in both retrofit and new build.
What the collaboration might look like
The three share common values, a passion for healthy high-performance homes, and a belief that technical know-how is not a barrier. They are open about not yet knowing the precise shape of the venture — whether it will be a single development or an entity that could deliver ongoing value. Early conversations have touched on low-rise timber housing, where margins are tight but the technical scope suits their skill set, and on the possibility of starting small to test the idea before scaling up. Funding options, planning constraints, availability of affordable land and the need for a core team member close to any future site have already been flagged up as potential challenges.
What changes for the podcast
Going forward, the podcast will shift its emphasis from individual self-build and retrofit projects to the nuts and bolts of getting bigger housing projects off the ground — exploring where the opportunities are, what the barriers look like, and how they might be addressed. Sally and Mike may drop in on future interviews or feed in questions behind the scenes. The commitment to high-performance, healthy, low-carbon homes remains the beating heart of everything, but the lens has widened from showcasing finished projects to actively trying to build them.
Dr. James Glockling explains how insurance works and outlines some of the challenges of insuring a natural building.
Interview with Dr. James Glockling
Dr. James Glockling began his career with the Loss Prevention Council, the insurers’ hub for studying fire, security, flood and other loss‑mitigation challenges. He later deepened his expertise at the Building Research Establishment (BRE), and then worked at the Fire Protection Association before setting out on his own as a consultant. His clients are wide-ranging, including insurers and even the military, helping them build resilience and mitigate risks in high‑risk scenarios—from multi-storey apartment blocks to the confines of a submarine. His work reminds us that, regardless of setting, safety rests on the same timeless principle: robust materials and well‑designed systems protect the people who depend on them.
In this podcast interview we discuss everything from one-off homes to high-rise, multi-dwelling projects.
Insurance protects the individual against disaster
Insurance began as a collective safety net, allowing many people to share the cost of rare but catastrophic events. By pooling premiums, an insurer can compensate an individual when a loss occurs, turning an unpredictable disaster into a manageable financial outcome. This principle still underpins modern home and commercial policies, even as building practices evolve. Understanding insurance as a partnership rather than a pure expense helps homeowners see it as part of responsible building.
“Insurance was originally set up as a means of protecting people against disaster, where you levy a premium on a large group of people to protect the interests of the individual.”
Insurers have to weigh up a variety of risks
Underwriters assess far more than fire. They examine the building’s use, size, occupancy, and any ancillary systems such as solar panels, battery storage, EV chargers, green roofs, or underground car parks. Factors like these may have an impact, so insurers request detailed information on design, materials and mitigation measures. The broader the picture they have, the more accurately they can price a policy and set conditions.
One-off homes should be easier to insure
As insurers always have to think about a complete loss and rebuild, having a single smaller property is a limited loss scenario. As the scale of a building increases so does the potential loss scenario.
Estimated Maximum Loss (EML) is a key metric for insurers
EML is the insurer’s worst‑case estimate of loss from a single incident, expressed as a proportion of the building’s total value. For a 20‑storey tower, an insurer might assume only four floors could be completely destroyed, translating to a 20 % EML. When new construction methods make fire spread more unpredictable, insurers often raise the EML toward 100 %, which drives premiums skyward or leads to outright refusal. Demonstrating a defensible, lower EML is therefore a key part of the underwriting conversation.
Under‑insuring is a false economy
Many owners underestimate the true rebuild cost of their property, declaring a lower value to obtain cheaper premiums. If a total loss occurs, the payout will only cover the declared amount, leaving owners with a significant funding gap. Accurate valuation, combined with robust risk mitigation, ensures that the insurance policy truly protects the investment.
Insurance companies may have their own specialist areas
James says that he used to live in a thatched home and that his monthly insurance premium was what most people would pay for a year. This is because if a thatched roof catches fire then the house will be a complete loss. However, NFU Mutual have made this their specialism and are seen as the go-to provider. This is because they understand the risks, know what conditions matter and have a history in this area.
Water damage is the most common insurance claim
Water loss accounts for billions of pounds of damage each year and occurs far more frequently than fire. Burst pipes, roof leaks and flood ingress can rapidly degrade timber, leading to rot, mould and structural failure. Early detection systems—wireless tape sensors, automatic shut‑offs—are increasingly expected by insurers, especially for mass timber projects where hidden water would otherwise go unnoticed for months. Proactive monitoring can therefore reduce both risk and premium.
When it comes to timber, voids present a fire risk
As timber is combustible, the design of a building becomes crucial. Voids can allow smoke, heat, and flames to spread rapidly, bypassing sprinklers and complicating firefighter access. Mass‑timber panels (CLT, glulam) reduce voids but may be subject to smouldering, which can persist for many hours and even lead to the flames reigniting. These behaviours force insurers to demand rigorous fire‑stopping, compartmentation, and sometimes hybrid designs to keep the EML manageable.
It’s essential that fire‑stopping is correctly installed
Every penetration—pipes, ducts, cables—in walls and floors must be sealed with a fire‑stopping material. Missing or poorly installed fire stops create pathways for flames and smoke, dramatically increasing the EML. In light‑timber frames, the sheer number of voids makes comprehensive fire‑stop inspection essential. Regular audits, preferably by a dedicated Clerk of Works, provide the documentary evidence insurers demand. This may make a boring photo collection but it will be a valuable one.
“I haven’t been to any fire in a building where I haven’t found the fire-stopping either missing or misplaced or just absent.”
Hybrid designs with concrete cores satisfy insurers
In high-rise buildings, combining timber with non‑combustible elements—concrete cores, steel columns or concrete plinths—offers insurers a tangible safety buffer. A concrete core protects against fire spread, provides a stable fire‑fighter access route, and serves as a flood‑resistant base. Such hybrids offer the best of both worlds, with the carbon benefits of timber while delivering the structural and fire‑performance assurances underwriters look for.
Take photos during construction to provide evidence of good workmanship
Even the best design fails without quality construction. Insurers scrutinise records of on‑site inspections, photographs and sign‑offs to confirm that fire‑stops, penetrations and material installations match the approved design. A diligent Clerk of Works creates a paper trail that can be presented during underwriting and later claims, reducing disputes and speeding up payouts.
“Evidence is everything, and if there’s a Clerk of Works properly reporting on the job as it’s put together, then that can only be of great benefit.”
Insurers steer away from complexity
The industry uses six categories to describe the percentage of combustible material in a building. For example, Structural‑Insulated Panels (SIPs) are often highly combustible, pushing a project into the highest risk tier. When a building lands in the 100 % combustible category, insurers typically raise premiums sharply or decline coverage. Understanding these categories lets designers choose lower‑risk assemblies or offset risk with non‑combustible cores.
The Mass Timber Insurance Playbook is useful resource
The Mass Timber Insurance Playbook, co‑authored by Dr. Glockling and broker Philip Callow, lists 26 features that insurers evaluate in timber projects and offers practical mitigation strategies. It is freely downloadable from the Alliance for Sustainable Building Products website and provides a clear roadmap for architects, engineers and developers.
Increasingly AI is being used in the underwriting process
Insurers are increasingly using artificial intelligence to analyse loss data, identify patterns and refine risk models. By feeding detailed, high‑quality information from the construction phase into these systems, builders can help shape more favourable underwriting outcomes in the future.
Award-winning architect Kirsty Maguire shares her experience of designing and building her own Passivhaus on a challenging sloping site in Newport-on-Tay, Scotland.
Interview with Kirsty Maguire
Kirsty Maguire runs an architectural practice and consultancy in Scotland, that blends good design with environmental responsibility, to create buildings that people love. One of her clients used the phrase ‘dream catching’ to describe the process of working with Kirsty, who helps people explore what’s important to them and then turns their dreams into reality. Kirsty does this on all her projects, including her own and feels that building a house can be an enjoyable process. She remembers as an architectural student wanting to create a space for herself, to be part of that world and have that experience. It took over 20 years for her to pinpoint where she wanted to live, find a suitable plot and have the funds available to put this into practice. Here she shares her journey and experience of building her own home.
Accessing a number of plot opportunities is part of the process
The idea of building her own home was there in the background for a long time before she really started looking at sites. Her grandmother’s garden, which had an outbuilding that could be replaced, was her first serious consideration, but the timing was not right for her to do the project. However, the thought process she went through, developing her ideas there, became a stepping stone in the right direction.
When Kirsty is working with clients who don’t already have land, she will help them look at different plots to clarify what they want, what they need and what’s most important to them. Thinking about the future is also important, we don’t know what the future will bring, so having some flexibility is ideal.
Get to know what your plot priorities are
As time went by, Kirsty set up her own practice, went on some adventures, and then got a bit more serious about plot hunting. Some plots came up in Newport-on-Tay, where she was living, but although she visited them and did sketches none of them really floated her boat. But she could identify what was important to her in this location; she had to be able to take advantage of the stunning views, be able to walk to the shops, be part of a community where she didn’t have to drive everywhere. Other people will have different priorities in their plot finding, so it’s knowing what’s right for them.
Eventually Kirsty saw an advert for the plot where she now lives when she was travelling on a 10-month sabbatical. When she came back, she realised it was a great spot, a really challenging site, steeply sloping, north facing site, amazing views, but it turned out someone else had bought it. She was disappointed, which was really telling, but it came back on the market and she managed to buy the plot.
A site with a lot of constraints can become a positive
Kirsty describes it as a tricky site with strict planning restrictions, which limited the overall size of the house, the direction of the build, number of bedrooms and amount of parking. There was also an existing planning consent for a dreadful building all of which put other people off the site and worked in her favour.
It was a garden when she purchased it, but Kirsty believes it was always seen as a building plot, with the house next door maybe having bought two plots, but never getting round to building on this one.
The main challenge was the topography, as it’s a narrow site on an extremely steep slope. There is a three-storey level difference between the front and the back of the house. Properties on either side restricted the placement of windows and she needed to ensure the right to light as well as making sure she wasn’t overlooking the other properties. From a Passivhaus point of view, it’s north facing, which is a challenge and most of the views are to the north.
In Kirsty’s experience once a site has planning permission it is much easier to adjust the details of the building, if you keep within the parameters of the local plan. Kirsty took all the restrictions that had been imposed on the site along with the physical nature of the site itself and used them creatively to create the shape of the house.
A lot of the core decisions fell into place
Kirsty knew she wanted it to be a Passivhaus using eco materials, so from that point of view, some of the design decisions were already made. As timber frame building is traditional in Scotland, this was also an obvious route.
‘Upside down’ living is a good fit for a sloping site
Kirsty describes her home as an upside-down building, with an open plan, living, dining, kitchen area upstairs. This has a partial separating wall with holes in it, so that you can sit at the dining table in the south facing sunshine next to the garden and also see the views all the way to Dundee. It’s a two storey, rectangular box with a pitched roof, but the ridge of the roof runs front to back, which is the opposite direction to what you might expect. There is then a box on the side, to accommodate the stairs, bathroom and utility. From the street you see the gable end of the building, with the ground floor of the building already a storey up above the street, and then it’s two storeys up above that to the ridge. The living space is a tall, generous space, where you could potentially add a mezzanine, but Kirsty doesn’t need any more space.
Thinking about privacy is also part of the window design
Kirsty knew that she wanted a big window to the north to enjoy the views and some rooflights to get east and west sunlight into the building to make sure it was light and bright. But, as well as ensuring that she wouldn’t be overlooking other people, she didn’t want them to be overlooking her. She therefore did lots of sight line analysis, which resulted in the big picture window in the living room being raised by 400mm. Architecturally, you might have put in a floor to ceiling window, but having the raised cill gives a huge amount of privacy. People walking along the street, or even in the house opposite, can’t see in and likewise, when Kirsty is sitting on her sofa, she can’t see out.
Talk to your neighbours to get their support
Kirsty went round to her neighbours to make sure they knew what was happening and that resulted in lots of letters of support for the building. It’s important to acknowledge that you will be changing people’s local area and most of us don’t like change. If we feel included in the process, we tend to be more comfortable with it.
The people opposite had built their own house and Kirsty’s house was going to slightly reduce their access to sunlight because of the steep slope, but they were positive because she had thought of them and worked out how to minimise the impact on them. She also feels lucky because the people around her are really friendly.
Variety in the neighbourhood is often a good sign for a self build
Kirsty thought a lot about how the cladding of the building would fit into her neighbourhood. There is an eclectic mix, with Victorian buildings, a 1990s period piece opposite, a small brown bungalow next door and some lovely new builds in the village. So she ended up incorporating motifs from some of the buildings around, the big picture window is echoed in the building next door and some of the Victorian buildings across the street, as is the relationship, with the pitched gable roof.
Some features of the house were not optimal for achieving Passivhaus
Kirsty explains that some of the constraints led to architectural features that are not optimal in terms of Passivhaus. For example, there are rooflights because she couldn’t have many windows in the walls along the length of the building. Also the desire for a big open space with a cathedral ceiling creates extra volume to heat. All this means is that the insulation must be slightly thicker to compensate.
The form factor is around four, which is similar to many of the detached buildings that Kirtsy works on. For the Passivhaus certification Kirsty used heat load rather than heat demand. The heat demand is calculated at around 20 kilowatt hours/m² per annum, whereas the heat load is 10 kilowatt hours/m². Her actual energy use is more like 13 kilowatt hours/m² per annum for heat demand, which is a lot lower than the PHPP had suggested. One reason for this might be that Kirsty prefers setting the temperature a little lower in winter at 19 Celsius rather than 20 Celsius.
The size of the windows matters
Kirsty stresses the importance of getting your windows the right size, both in terms of heat loss and overheating. It might have been tempting to open the whole south gable end to glass, but she knows she would have cooked in the summer. She still has one large feature window and several other generous sized windows, and says the PHPP process really helps to show where there might be a problem and how to adjust things accordingly. Even though it’s looking at averages and could be regarded as a crude tool it did allow her to model her overheating risk to 0%.
Skylights can be tricky to shade
Kirsty included skylights as replacements for vertical windows along some of her walls and explains that you will lose more heat in winter through a window directly facing the sky and it will be harder to shade in summer. She doesn’t feel she has enough of them to cause a problem and one benefit is that they work extremely well for stack ventilation.
Strathclyde University have been monitoring the performance of the house and office for the last 18 months and both of them are working really well.
Finding time to work on the project was challenging
Kirsty is building houses all the time, so from that point of view, building her own was quite straightforward. She knows good consultants who are part of her normal work team that she could bring into the project. The hardest thing was setting aside enough time, because she was having to do all this in her own time. At least she was passionate about it, but remembers finishing some drawings whilst on holiday with friends!
Be prepared for a lot of digging out on a steeply sloping site
The groundworks phase started with digging out a lot of material from the site due to the steep slope. There was also a 2.5m high wall along the street edge that had to be taken down and soil removed to make it level with the street to create the parking area and the site for the new office. Kirsty was able to reuse the wall to create the gabions needed on site and collected more stone from other building projects around the village. And her dad even carved her house number onto a piece of stone, which was built into the new wall.
The house is on an Isoquick raft foundation, with the area around it built up with a concrete block retaining wall, which is insulated on the outside with XPS insulation. There is also a tanking layer to keep the water out, which so far has been working well. Around a third of the building sits below ground. The timber frame is filled with wood fibre insulation with a wood fibre “tea cosy” all the way around the outside including the roof to avoid thermal bridges. Kirsty often uses this technique, particularly when doing a stick build on site. She explains that there used to be few timber kits of Passivhaus quality that were manufactured off-site but now there are some good ones, including Eden Insulation that was used at The Seed.
Find out more about Eden Insulation in our training session with Stephen Gurney in The Hub.
The steep slope also meant it was harder to bring materials to site
Everything had to be carried up the steep slope, most of it by hand. Only the large windows and ridge beam were brought in by mechanical means. Kirsty says it’s also worth checking the largest size of window that can be carried on a normal truck, so you don’t have to cover the cost of non-standard transport.
It’s about choosing where you spend your money to make the best impact
Upstairs, there is lots of volume due the cathedral ceiling and this gives it a light and airy feel. There is oak flooring throughout the house with quite simple detailing and lots of plants adding interest. A local craftsman, Imric made some beautiful shelving and built in cupboards, with bespoke worktops coming from another craftsman in Edinburgh. However these items sit alongside an IKEA kitchen, Howdens flooring and bog-standard skirtings, architraves and doors.
Kirsty tells us that people often comment on a yellow globe light that can be seen from the street, which cost £20, whereas other handmade more expensive light fittings go unnoticed. She also made light fittings herself using coloured cable and used a number of long drop cables to separate spaces. It’s not just about putting up walls up to separate spaces, there are more subtle ways of dividing spaces that create layering and different views.
If you have a dream explore it with an architect
Rather than always wondering “what if”, Kirsty’s advice is to find an architect to help you to explore your dream building. It doesn’t mean you are committed to the project at that stage, but it’s good to put all your ideas on the table, sift through them and see where it takes you. You’ll probably end up prioritising them, but later you might find a way to return to these ideas that were less of a priority at the start. Kirsty loves going through this process with clients, even when they don’t know how to articulate what they want, because there are so many opportunities. She finds getting to know her clients and creating that relationship with people a really special part of being an architect. She sees private clients as really invested in the process, with many of them bringing so much of their own creativity to the conversation.
Passivhaus delivers a healthy and comfortable internal space
Kirsty sells this level of comfort to her clients and visits them in their houses but still thinks it’s difficult to understand how great it is until you’ve lived in it yourself. She was living in a small, 200 year old flat before building this house, which had all the pros and cons of an old building, but is mostly cold and slightly draughty! Much as she liked being there, she can’t really express how comfortable she is now and how nice it is to have constant fresh air.
When designing the building, Kirsty layered up so many interactions between the spaces, some subtle and some not, to capture different views. She finds it hard to pick out one thing as a favourite, but it’s probably the views through the building, being able to sit in the living room and look out all the way across the Tay Estuary to the mountains.
Sally Godber, a Director at WARM consultancy explains why reducing the risks on her own Passivhaus project was so important, what that entailed and how it enabled her to deliver a healthy, comfortable and energy-efficient home on budget.
Interview with Sally Godber
Sally is a Chartered Mechanical Engineer and Passivhaus certifier who co-founded WARM consultancy with her father Peter Warm. She grew up with her dad building different houses, always experimenting with designs and construction systems to improve energy efficiency. It was never her intention to work in this field but somehow it had seeped in by osmosis, and after university and her growing awareness of the climate crisis she wanted to work in sustainability. With her engineering background she had gone into building service design, but it wasn’t rounded enough for her as it only dealt with a small part of the building process. Combining her experience from the commercial sector with her dad’s hands on practical experience and knowledge of domestic builds resulted in WARM energy consultancy. Their services include Passivhaus consultancy and certification, focusing mainly on commercial building projects. They also offer training through their sister organisation, Coaction.
The juxtaposition of her work and her home situation became too much
The driver for taking on a project came after living in a large, damp, Victorian house, whilst working on Passivhaus projects for other people. Initially Sally and her husband Mikey had started looking for a new home, but they found themselves wanting to change everything other people had done, which felt pointless. Either they needed to find somewhere that required a lot of renovation or to start from scratch.
Managing risk became an integral part of taking on a project
For Sally the prospect of taking on a new build or retrofit was exciting, but her husband Mikey was not so sure. So when they sat down at the beginning to discuss their priorities, risk came up. For Mikey, above anything else he did not want to be crippled financially by chasing the self build dream. Luckily a large part of Sally’s professional life is spent de-risking projects and also having had ‘the big house’ experience she was after the polar opposite.
Scaling down a project scales down costs
With a tight budget one of the most important decisions you’ll ever make is setting the size of the project. If you make it too big then it will be impossible to get the quality you desire. Sally and Mikey wanted to build to Passivhaus standard, but beyond that they just wanted a modest sized, warm and comfortable family home.
“We had a young family, I had my business going on, and my husband was not totally sold into this. We really needed something that was going to be low risk. So all of the design work that we did was about being able to manage the budget.”
Risks can often be identified
Sally outlines multiple risks and how many of them can be reduced through good design. She explains that some risks start with our expectation about how a project is going to go and then the reality of what actually happens. We might be faced with cost increases or there might be a failure during construction, for example, through something not being protected on site, which results in water damage. In terms of the energy performance, the airtightness, the insulation continuity and the build quality are key. Sally sees projects go wrong when the contractor is not clear about the expectation for the build, or the design contains many complex details, which have been hard to price in advance. Although it’s a quantity surveyor’s job to cost up projects, when the design is complicated it’s much harder to work out accurately the time and effort needed to complete the build to a decent quality. So, the difference between the client’s expectation and reality could be quite significant.
Reducing the number of ‘unknowns’ reduces the overall risk
Sally will always look to pay a fair price for building work which has got the least of number of unknowns within it. She explains that it is impossible to take some guesswork out of retrofit projects because you can’t know what you are going to find. Likewise, there are always some unknowns around groundworks, but for a new build, once you are out the ground, the risks come from the things that you’ve added into the design.
Complexity increases risk
This means that the amount of risk you have on your project is down to how complex you’ve made the design. These risks can come from the geometry of the building or the construction choices. Sally explains that making good decisions during the design process may not save you money on paper, but reduce the risks of you having to build to a poorer quality and it not being what you wanted.
“The amount of risk that you have on your project is about how complex you’ve made the design.”
Know your absolute price when buying at auction
Sally and Mikey considered a few plots and existing dwellings, before spotting a dilapidated pub at auction. Key opportunities included it being in a great location in Plymouth, which was at the entrance to the historic naval victualling yard and near to the WARM office, and having a sizeable garden with a beautiful old Holm oak tree in it. So they decided to bid for it.
A top tip that Sally received from a friend is to work out your absolute maximum offer in advance of attending the auction and then not to go above it! While this may seem basic advice, as a novice it’s easy to get swept along in the moment.
Sally also gets the feeling that most people at auctions are professionals, who are representing investors, so you will be competing in this arena. However, overall she thought it was a great way to buy a building, particularly because it’s so quick. Their last bid was their absolute maximum, so the adrenaline levels were high but they secured the property.
Living in the pub gave them a better understanding of the work that was needed
The pub had a flat upstairs, so they decided to live in it for a year to help get an idea of the space and make sure they understood what the retrofit required. They quickly realised that the pub was more dilapidated than they had thought, it wasn’t well connected to the garden and the refurbishment would cost a lot more than they were planning to spend. So they explored another option instead, which was to build a new home in the garden and then refurbish the pub at a later date.
Achieving planning permission was an emotional roller coaster
Sally has a lot of empathy for people who have been through the planning process or are going through it, as it was a real headache. It didn’t seem to matter that they wanted to build a good quality, high performance building that would fit into the local environment and last for generations. It felt like a lottery, particularly when they’d had a positive response to their pre-application, only to be turned down on their full application. Luckily their architect Jae Cotterell got involved and was able to present a good case for why it should be granted, and the planning department eventually saw sense and gave it the green light.
Working with one company for the design and build was part of their original de-risking strategy
Sally tells us that part of their de-risking strategy was to get Passivhaus Homes involved. Not only did they supply a kit that was tried and tested, and would easily reach the Passivhaus standard, but at the time they were also doing the construction work. So keeping the design and build with one company was a way to get cost certainty.
With her second child on the way, however, Sally was keen to get moving as soon as possible. Unfortunately the time frame for Passivhaus Homes to carry out construction didn’t work out, so they considered another option.
Their simple design made it easier to engage with another timber framing company
The positive side of all the work they had carried out in the design stage to de-risk the build meant they could approach a more standard timber framing company.
A simple design reduces the risks during construction
The house has a simple rectangular form with a pitched roof. On one side there’s a single storey element with a flat roof to provide a view for their neighbours. This added some complexity to the detailing and being close to their neighbours also meant they had to lower the eaves on one side of the roof.
The floor area internally is 120m² and it was a priority for Sally to make this space work hard. Downstairs is an open plan living room and kitchen, which has been designed so that a wall could be added later if they ever want to separate the rooms. There is also a spare bedroom downstairs, along with a utility room and a downstairs bathroom. Upstairs, there are three bedrooms and one bathroom.
The emphasis was on making the spaces work, with Jae encouraging them not to scrimp everywhere! For example, creating a welcoming and spacious hallway was something they didn’t appreciate at first, it felt like a waste of space, but over time they have realised how valuable this is.
There were challenges using a standard timber frame
Sally explains that Passivhaus Homes use a portal timber frame, which doesn’t require a ridge beam and allows you to create spans without any supporting beams. Unfortunately, standard timber frame manufacturers are not used to doing the lift of the ground floor and first floor in one which is what you do with a portal frame. Separating it into a ground floor timber frame and a first floor timber frame meant that they needed steel beams to provide support. Sally hadn’t wanted to use steel as a material in the build and this then created some difficult detailing for the airtightness. This is where the standard timber frame suppliers really struggled and if it hadn’t been so late in the design process Sally would have changed the design to break up the spans, so they could still have used timber. She feels it’s really important for designers to understand the natural limitations of different materials rather than relying on engineers having to solve problems because you’ve created a span that’s too wide.
Allwood Timber supplied the twin stud frame, which was then filled with Warmcel insulation. They have insulation under the slab and the roof is treated the same way as the walls, with blown-in cellulose. The structure is I beams, with OSB board on the inside.
Another advantage of a simple design is that you can run your eye over everything to see it’s all in order, such as making sure the airtightness line is continuous.
Remedial work enabled them to achieve the airtightness target
They did some of the taping themselves, along with the timber framer and after a poor first air test (1.2 air changes per hour at 50 Pascals) they realised they hadn’t pressed down the tapes enough. As soon as they did this and activated the glues, they saved another 0.2 on their air test. There was also air leakage around the steel beam. If she’d done the project today Sally would have used an airtightness paint to sort this out, but back then she had to spend a late night putting a lot of tape on it. Their final air test achieved 0.56 which meets the Passivhaus standard performance criteria.
Their windows and doors are from Rationel, because Sally had used them before and knew they were relatively cheap in comparison to others. They also designed all the windows so that they could be openable with a single span, with a lot of them being top hung so they could leave them open at nighttime. They’re a simple design with easy detailing, which all helped during construction. Sally feels it was still hard to achieve good airtightness when they didn’t have a lot of time themselves to check things and weren’t working with people with experience of this type of build.
They achieved a better airtightness with the pub retrofit a few years later, working with a local contractor called Greenacre Design and Build who had an amazingly skilled team. They were great problem solvers and fantastic at detailing, so they did exceptionally well even though it was their first time doing a Passivhaus retrofit project. But sometimes you don’t have those teams, and so being able to keep the details simple is really helpful.
Sally took over managing the build as soon as it was watertight
Sally made the decision to take over the project once the building was watertight. This meant they could project manage, be in control of the individual contractors and communicate directly with them. For example they got a contractor in to do the plastering and did all the services themselves, apart from the final electrical bits. They brought in a friend, a carpenter, to do the internal finishes and he refused to use soft wood! This really put quality into the build and is now much appreciated by Sally and her husband. It did take longer to complete the build as they were quite restricted with the time they could make noise in the evenings and at weekends, but it was good to feel more in control.
“We found that once it’s watertight, it feels like you can just breathe a bit, and it’s a bit easier to manage.”
It’s worth taking the time to get things right
It took two years from the point where they bought the pub to them being able to start construction and one year to do the build. The first year was deciding what they wanted, going from the pub renovation to a new build, then another year designing and getting planning permission. At the time all the faffing felt frustrating, but seven years on she can see that it was worthwhile and meant they ended up with a better home that will last them much longer as a family.
Sally had also learnt from her parents’ projects that it’s best not to move in until the house is finished as the work just doesn’t get done after that. One of the things they hadn’t done was tile the kitchen, which was only done six years later!
The house was delivered on budget, but the time put in hasn’t been calculated
It was a real success for them to deliver the project on budget, but with a self-build the amount of time put in is huge and something Sally doesn’t want to calculate.
There were some complications during the build, not necessarily associated with the design and things that they would definitely do better next time. They were very careful and conservative to achieve their budget and there are some things they might want to be different. Luckily noticing the faults wears off with time and over the whole project there is just one window that Sally wishes was larger. She was worried during the build that they were being too careful and maybe the building would feel mean, but it doesn’t.
“If you are on a tight budget, it makes a huge amount of difference feeling in control and that was ultimately why we took on the self-build.”
Managing the contractors themselves meant there was no middleman, they could negotiate individual prices and have conversations about the materials they were using.
Sally describes herself as a Passivhaus geek, but even so there was so much she didn’t know. This has given her a huge appreciation of all the different skills needed in a team to complete a build project.
She tells us how she really enjoyed the whole experience, both stretching her mind and also physically doing stuff. She doesn’t think there’s enough of that crossover, with designers getting practical hands-on experience. With the pub finished three years ago she’s definitely ready for another project but has nothing particular in mind.
Sally got to appreciate Passivhaus certification from a client’s perspective
They had designed the house to Passivhaus standard but hadn’t discussed certification until they were just about to start the build. Sally tells us that at the time she was absolutely exhausted and didn’t think she had the energy for it; it would be just too much hassle. Her dad, who doesn’t often tell her what to do was very clear that not doing it wasn’t an option, particularly considering her job!
They employed Will South of Etude to do the certification so that they had someone independent looking at the project. In the end, the certification process proved incredibly valuable for Sally as she knew there was a second pair of eyes checking on the project details. She was doing her best to check things but was incredibly busy and Will picked up on a few things that were wrong. Will had identified that they’d got their shading wrong, which they were able to correct, but it was too late to change the insulation, which was not the right specification. They had enough margin in the calculations for this not to matter, but by identifying it early they could have made adjustments elsewhere if they’d needed to.
It also gave Sally a real appreciation of just how hard it is as a client getting everything together for certification and the need to find the right level of checking. She is still a massive advocate for certification and as there’s very little quality control it’s good to have someone whose sole job is to check that you’ve built what you said you were going to build.
Sally’s husband is now an advocate of Passivhaus!
Sally says her husband wasn’t totally onboard with MVHR, triple glazing or even achieving the Passivhaus standard, but she was clear that these things would be worth it. They’d moved from a large Victorian house that was uncomfortable and difficult to manage into a tiny pub flat where she was cleaning mould off the walls. The flat was just 60m² and inevitably there were arguments and conflict. So, the experience of moving into somewhere that was a lot bigger was obviously like a revolution for the family. Sally tells us that it was so warm in the house that the kids wouldn’t believe they needed to put on coats to go outside. She had been spouting the theory to everyone, but it was still amazing to experience the comfort and warmth for herself. Her husband was quickly converted to this way of living. They also realised how they’d stopped inviting people round to the pub flat because it was so damp and at the time Sally hadn’t realised just how much inherent stress the mould and the dampness were giving her. She admits to being a total snowflake now, finding it very difficult to stay in other people’s houses.
Try to enjoy the whole house-building journey
In hindsight Sally reflects on the self build journey as a really lovely process, but this is not always how it feels at the time. She gives an analogy of when you have young kids you can feel like your hair is on fire, you’ve got sick down your front, and you’ve just stepped in something you’d rather not have. But when you look back, you think that was an absolutely incredible experience. She says to find ways to bring your family together through the process and the same with your wider building team. The relationship side of a building project is really important. So, as much as possible try to enjoy the sick down the front feeling!
Janice Gardiner reflects on her eco build and shares ten of the most significant lessons from the project.
1. Spend time thinking about how you want to live in your house
We knew from the start that we wanted to build an eco house so contacted architectural practices that specialised in eco builds and soon found Green Trace Architects. Our architect, Joshua Wood, then took us through a process to determine our values, how we wanted to live in the house, how we wanted the spaces to interact with each other and what we wanted it to feel like, before any designs were put on paper. For us sustainable materials, along with a social space for family and friends to gather was important. We also wanted to feel that the house was connected to the land around it. This informed Josh’s designs which included a large open plan living area, a wood panelled ceiling, clay plaster walls and large windows that connect us to the outside. The end result has lived up to our vision.
2. Visit other self-builds of a similar style
Whilst researching different building systems Josh came across EcoCocon and discovered the architect Juraj Mikurcik had built with this system just up the road from our site. Juraj kindly showed us round his house, Old Holloway, which was the first time we experienced what might be possible. It’s all very well talking about and seeing images of Passivhauses, but it’s only when you experience one that it really sinks in. There was a calmness and a feeling of peace that had quite an emotional effect on Colin and that was the moment when we could imagine how fantastic our build could be. Juraj was also able to pass on lots of useful advice and ideas, which we incorporated into our designs. This included getting rid of the wood burning stove and underfloor heating as in his words they operate as very expensive pair of slippers. The reality is that we only need minimal additional heating in the coldest months.
We didn’t go for the EcoCocon straw system, because we were building in the winter and didn’t want to risk the straw panels getting wet. In the end, we had a very dry winter and EcoCocon may have been an easier material to apply the clay plaster to, but that is just how things go.
3. Understand the planning process
We bought the land with outline planning permission, but no design for the new dwelling, which left us free to submit our own designs. Permission had been granted based on replacing an old wooden building, with the condition that the new house could not be more than 100m2 internal floor area. This is relatively small, but by including the double height ceiling over the dining area, Josh was able to increase the house footprint and make the house feel more spacious. Upstairs the roof line slopes to the floor in places, and anywhere where the height is 1.5m or less is not included in the floorspace calculation. Again, this added to the house volume and these areas became useful storage with built in cupboards. These design features have made the house feel bigger without adding to the internal floor area, showing that you can be creative within the planning restrictions.
Whilst we never wanted a large house, in hindsight we could have made an argument to make the building slightly bigger. Areas like the second bedroom and the plant room would have benefitted from a few extra square metres and the site itself could also take a larger property.
4. Do your own research even if you have a project manager
As novice builders we were not sure what we didn’t know and maybe relied too heavily on the professionals around us, who didn’t always realise what we didn’t understand. At times it may feel like you’re speaking different languages! For example, with the cost of the round window we just thought about the actual window, not how it would fit to the external tin and how to produce a curved frame. So even though everyone was saying this will be expensive, we didn’t really get the whole picture. Doing research into the different stages of the build and becoming familiar with the different processes would have helped us to ask better questions and make more informed decisions.
5. Know your own strengths and weaknesses
Personality traits are important, as they will influence your decisions, so really think about what you are good at and when you may need extra help. We knew what we wanted, had dreams of a Passivhaus, had watched Grand Designs avidly for years, but never thought we would be in the position to do it. So, when faced with a simple design or a more architecturally interesting one, we were instantly tempted by the latter, which inevitably led to us spending more money! Our original design also didn’t include solar panels or aim to be Passivhaus certified, although we did ideally want to do both. So, when we found out our builder was also a solar panel engineer, and the designs were actually achieving Passivhaus standards we went for both. Consequently, we really stretched our finances but have achieved a better outcome. In general, we are better at interior design than sticking to budgets!
6. Work with people with similar values and trust them
The desire for an eco-build influenced our choices from the start and what we hadn’t realised is that Herefordshire is a hot spot for Passivhaus builders. Serendipity brought us Dai Rees, The Passive House Builder, who lived just 8 miles away. Dai and his team were brilliant to work with, had wide ranging skills, including carpentry and tiling, and put so much thought into making the house as beautiful as possible. One example is the internal wooden ceiling. Juraj from Old Holloway shared a photograph of his ceiling, where with 3 widths of timber he created a pattern that appeared random. Dai and his team painstakingly replicated this and then added new edging to create a slightly different feel.
Inevitably there is problem solving needed during the build and it probably would have been useful to have had Dai on board before Josh’s designs were complete. This would have allowed them to work through some of the technical aspects together, like how the roof met the main beam, before starting the build. The downstairs shower room was another conundrum, with the design only getting finalised late on in the build.
7. Your builder will follow your architect’s plans
That may sound obvious, but we did forget that the plans contained things we weren’t totally sure about. For example, Josh was aware that we were doubtful about the external low wall around the front of the patio, but Dai was not party to those discussions, so footings for the wall were in place before we realised. In the end we didn’t build the wall, so work had been done unnecessarily.
8. Effective and timely communications are important
We found we were quite redundant in the early stages of the build; Dai was following Josh’s plans and we weren’t really needed. But when it came to the fitting out, we suddenly found we had numerous decisions to make. The first thing was:
“Where would you like all the electrics? The electrician starts next week!”
These weren’t on the plans, so a few late nights were spent working out socket positions, lighting and light switches. We had been a little naïve about this aspect and maybe too laid-back. We then had to look at light fittings, toilets, bath, showers, tiles, kitchen design and fittings, staircase, interior doors, handles – everything that goes inside a house needed to be chosen and sourced. Sometimes these decisions are needed to be made before the structures/walls were even in place, so it was hard to visualise the end result. How do you choose the colour of bathroom tiles when you have no walls or green OSB board as your backdrop? Never mind that every space looks so small before the walls are in place!
Good fun when you get your head around it and you will never have to make this many decisions so quickly ever again in your life… unless you build another house.
9. Look at different financial models
We went for a cost-plus approach, where we had a broad indication of the cost of the build at the start, but were open to any fluctuations in material costs during the build. In effect we held the risk for price increases but potentially could also make savings along the way. Timber prices increased during this period of time, but we also chose a more cost-effective roofing/cladding material. We trusted our builder to get us good prices, and it gave us lots of flexibility during the build, but it was harder for us to keep on top of costs. We would also agree to things without asking for the full costs, often not factoring in the labour costs of a particular item, such as a custom-made sink unit for the main bathroom.
Basically, we were dealing with a changing budget rather than having things agreed up front through a fixed price build. In some ways this flexibility suited us and resulted in better finishes, but it did mean we spent more overall.
10. Don’t aim for perfection
Things will inevitably go wrong, hopefully minor and easily put right, but problem solving is part of building a house. Sometimes potential problems will be spotted early on and so can be avoided. For us, it was Dai realising we needed to make one of the walls in the plant room removable in case the boiler broke down. We were very glad he did this as the boiler was faulty on installation, so had to be taken out and replaced straightaway. Other times you will make decisions you end up having to live with. For us, not putting a hand basin in the downstairs shower room was one of them. Water pipes and wastewater points are put in with the foundations and at that point we hadn’t decided on the layout of the shower room. As it was small, and we didn’t know how the shower doors would open and we decided to do without a handbasin. The room was next to the utility, which has a sink and most of the time this is okay, but it’s not ideal for people staying over. We can now see there actually would have been plenty of space for a hand basin.
Working with a good team certainly made the build an enjoyable process for us. It didn’t necessarily stop us worrying about the decisions we were making, but that’s part of building a house. We now have a beautiful calm home that sits lightly on the land and will look after us for many years to come. We still have lots of external landscaping and gardening to do, but luckily we like doing that!
Mike Whitfield shares his experience of running a local construction company that specialises in Passivhaus. He explains how the business is structured, and what tasks are tackled on a daily and weekly basis.
Interview with Mike Whitfield
Mike Whitfield, the owner of Mike Whitfield Construction, began his career in his early twenties, working in America, Canada, and Australia. He had always wanted to be a carpenter and learnt about timber frame building whilst working abroad. Returning to the UK in the 1990s he got involved in oak frame construction for a while before rekindling his interest in energy-efficient buildings. The AECB was a great source of information to keep at the vanguard of green building, and so Mike was well placed to take on Passivhaus building when it came on the scene.
Once Mike Whitfield began to focus on building high performance homes it naturally led to more of this type of work. So from 2010 onwards nearly all his projects were to Passivhaus or EnerPHit. As these projects require a greater attention to detail and high quality workmanship, over time Mike Whitfield Construction has built up a reputation of being able to deliver.
In fact, as they are seen as the go-to Passivhaus builders in Herefordshire, Mike even believes they may have missed out on jobs!
“If you get a reputation for being too busy, you can miss out on jobs. People say I didn’t bother asking you, because you’re always busy.”
A core team of people is key to his way of working
Mike explains that he has a core team of people employed by his company. This is different to the typical British builder model, which uses self-employed subcontractors on ‘zero hours’ contracts.
Being part of a regular team makes it possible to develop skills and knowledge, which is essential to a Passivhaus project.
One of the advantages of being a well-established company is that Mike has built up a network of additional collaborators, from architects and groundworkers to electricians and consultants. It all helps the operation run smoothly.
A local builder can often end up wearing many hats
Mike is now 67 and trying to step back and hand over the reins to others.
This has been an interesting process because he’s been able to contrast where the business is today, as it moves to become employee owned, versus how he started as a sole trader.
In the early days, as is common with many small builders, the paperwork gets done in evenings or over weekends (which means working long hours each week).
As a more established company of 11 people today, Mike has been clear that there needs to be more than one person stepping up so the load can be shared in a more sustainable way.
There’s now a slightly different structure in place. For example they’ve got two site foremen, with one taking on more responsibility for liaising with the clients, and the other one able to concentrate on the construction. An office manager is also in place to handle the paperwork and order materials.
Maintaining momentum requires good communication and organisation
Mike’s work has changed recently now the foremen are taking on more responsibility. However, even with the new structure the same key tasks need to be completed.
There’s a briefing on site at the beginning of the day so that each team member knows what needs to be achieved and can get to it. There’ll be various aspects for the foreman to oversee, such as the quality of work, the progress, and receiving deliveries.
There’ll be meetings with the client or consultants, always looking ahead to the next steps.
And in the office there’ll be various ordering and invoicing.
“It’s just a question of keeping the materials flowing to it, making sure our office manager knows what’s going on and our office management system is working well. In my previous life I was on site at 7.30am to get people going, then in and out of the site hut organising things. I’d be lucky to do an hour or two of the practical work before leaving at 3.30 to go back to do a couple of hours work in the office.”
Mike prefers a ‘collaborative procurement’ process
Drumming up new business can be a process that takes years. It might start with a phone call from a potential client, who is looking for a plot of land. Mike would normally refer them to the architect he works with most frequently. It might go quiet for a couple of years, and then finally the discussions about the design begin.
Costing a new scheme draws on data from previous projects
Mike has detailed records for the outputs and costs for each stage of a build, so he can input prices at the design stage. He calls it a collaborative procurement, rather than doing a tender or some other method. A lot of architects in the Passivhaus world now accept that it can be good to find a builder you like and trust, and just work up the price with them.
“Working from a basic sketch we can have a good go at pricing the build using our previous experience and our pricing programme. If we know the client’s budget, we can work with that and assess what is possible for the money. Mutual trust is important.”
The team must always be working on a project
One of the trickier elements of being a builder is keeping a steady flow of work for the whole team.
Mike describes the ideal scenario being where their groundworkers have started the next project, whilst his team is on the main project, and maybe one or two people are second-fixing the last project.
Of course life doesn’t unfold perfectly and sometimes they have to do things differently.
Mike shares an example from last year when he had two jobs running in parallel. Luckily, they were only a few miles apart from each other, which helped.
A builder will often have a site on standby for quieter times
When there are gaps in the schedule Mike can move the team onto one of his own projects. He says last year they had three jobs, totalling £1.5 million, in the pipeline but couldn’t start any of them. So having a plot as a fallback option means they can divert resources to do part or all of the build. Again, in a perfect situation the team would be completing the whole project in one go, but they could just do the groundworks and pause, or they could get the shell watertight and then bring things to a halt.
Building to Passivhaus standard demands more from a business
In Mike’s experience, Passivhaus building requires more attention to detail and greater supervision, and the profit margins are tighter.
Although there is a lot of job satisfaction in delivering high quality buildings there is no doubt it is much harder than simply complying with building regulations. For a conventional build it is relatively easy to find a good site supervisor, use a quantity surveyor for pricing or give drawings to a builder’s merchant for them to work out the quantities you need. Mike has always had to do his own pricing and recognises it is harder.
Want to see how a timber frame project comes together? Check out our Buckinghamshire Passivhaus case study in The Hub
Track record is the best way to gauge a builder can deliver a Passivhaus
Mike thinks that clients who commit to building to Passivhaus standard have thought a lot about what they want, and therefore the service needs to reflect this. In the early days people would realise part way through construction that they’d taken on the wrong builder and they weren’t going to get a Passivhaus at the end.
It’s slightly easier now because a builder should be able to show you a portfolio of certified Passivhaus projects. If they’ve only completed one or perhaps just do ‘Passivhaus principles’ then this may be the point to ask a few more questions.
Pricing up retrofit projects is challenging
Although there is demand for retrofit projects Mike says they are certainly trickier. They’ve tackled 4 or 5 so far, and it took until the fourth one for them to make any money. There is an argument for doing them on a ‘cost plus’ basis as you don’t know what you’re going to find before you start.
However Mike generally prefers to work on a fixed cost basis, with everything agreed at the start and then its up to him to bring it in for that price. It can mean tight margins if prices spiral after you’ve quoted, but on the whole it works well.
It’s easier for builders to upskill today
As Mike gradually steps back from the business he reflects on his career in a positive light.
Some aspects of running a building company are tough, especially on your own, but he has always loved the craft of the work.
To others who want to follow in his footsteps and build to Passivhaus standard, Mike says that the good news is that there is a lot more information and training available compared to when he started out. It will demand more from you and your team, but if you’re up for a challenge and committed to this way of working it can be extremely satisfying.
“It is hard to find the right people, but if you can, and you’re all working together, it is so much easier.”
His advice to young people starting a construction company now is to find men and women who share the same goals as you, so you can form a team to share the workload and support each other.
Furniture maker Lucinda Leech shares her story of building a modest, but beautiful eco home.
Interview with Lucinda Leech
As a furniture maker Lucinda Leech has experience of working with many types of wood, has practical skills and attention to detail, all of which she has brought to building her own eco-house. Lucinda was at the forefront of the Forest Stewardship Council (FSC) movement in the 1990s and is aware of the complexity of issues around sustainably sourcing timber. Having “retired” from furniture making she was presented with the opportunity to build her own timber house. Acting as both project manager and worker it has become a labour of love.
We’ve got better at understanding what ‘sustainable timber’ is
In the early days, sustainability wasn’t even spoken about within the timber industry but by the 1990s it became a concern due to significant deforestation, particularly with regard to tropical timber. Lucinda did a lot of research and travelling to understand the reality on the ground. At the time people were saying, “mahogany is murder” and encouraging a boycott of tropical timber, but Lucinda believes that this just made the situation worse because the locals came to view tropical timber as worthless, something to get rid of as fast as possible, so that they could grow cocoa or coffee to make money. Lucinda and several friends worked with individual communities, rather than logging companies, to buy timber from them at a value that was closer to what would be paid for the final product. This cut out the middlemen and gave communities a reason to look after the forest, to treat it as a harvesting operation rather than clear felling like the large companies were doing.
Tropical forests are much more varied than our forests in the UK. To put this into perspective the UK has around 26-28 native species of trees. In Ecuador, Lucinda carried out an inventory on less than a hectare of land and found 136 species. When they repeated the research in a different village they found another 136, but only about 20 of those species were found in both. So Lucinda’s role was to find out how people used the individual timbers, to give an indication of how they could be used in the UK.
FSC and PEFC are two systems that identify sustainable timber
The project continued the conversation around sustainable timber and better sourcing, and eventually led to creating the Forest Stewardship Council (FSC). This certification system and others like the Programme for the Endorsement of Forest Certification (PEFC) provide trusted solutions to help protect the world’s forests and tackle deforestation, climate, and biodiversity challenges. So if you’re looking to use timber on your project, make sure it carries one of these certifications.
Site plan – copyright Architype
There was ‘a potential plot’ in her own garden
Lucinda has just over an acre of land in rural Herefordshire, with her existing house set over in one corner, which left scope to fit in a new house without them being on top of each other. She never thought she would get planning permission, but she tried and was successful! The sloping site has a number of trees on it, and Lucinda was keen to protect as many as possible, so it took two or three years to work through how to do it before starting the build.
A detailed brief is at the heart of the design process
Sustainable architecture firm Architype‘s Herefordshire office is a stone’s throw from Lucinda’s site and although they don’t usually take on one-off dwellings, as neighbours, on this occasion they were able to help. Elly Deacon Smith was appointed for the project.
Lucinda’s plan was always to retire to the new house, so she wanted a property that was small and easy to look after. It had to be big enough for her and occasional visitors, for it to be an eco-build, primarily made of wood, modest but beautiful.
“I wanted it to be an eco-build… primarily wood, modest but beautiful.”
Lucinda wrote a detailed brief before she started, broken down into different sections, what sort of space, the budget, what she wanted it to look and feel like. She believes that clarifying all those things before you begin is really useful.
They also slightly shifted the location of the house further up the slope to give access to more light and better views.
Lucinda says that she really enjoyed the design process, working with Elly, going to and fro with ideas, and refining everything. They were taking a Passivhaus approach which helped fix the orientation, the amount of glazing, the details of the structure and the amount insulation. In the end the house may not meet all of the Passivhaus performance criteria, as there were a few changes along the way, but it will be very close.
Choosing your team is an important part of the process
Lucinda didn’t want to work with a builder who was just going to take the whole thing off her hands, with her just visiting once a month to check on the progress. She admits that the company she used were remarkably long suffering, coping with the amount of time she spent on site and her input. They hadn’t built a Passivhaus before but were really keen to learn. They developed the design from the pictures that were drawn for planning into something that could be built efficiently and in quite an interesting way.
Challenges can always be overcome
Lucinda was in the builder’s office finalising the details, when the COVID lockdown was announced, so that delayed the start date. However, it also meant that her son and daughter came back home and were available to help with the project in their free time. Several of their friends also returned to the area, and whilst they weren’t allowed to meet socially, Lucinda could employ them all to work together on the building site. She feels that she benefited a lot from help during COVID, as well as it causing delays. Brexit was also around this time and the I-beams had been ordered from Germany which caused delays and fear that they may never turn up. By the time they arrived, it was mid-winter, so they couldn’t start work until the following spring. There was a lot of stopping and starting, and then the actual structure went up quite fast. But then there was a lot of waiting around for other things to happen and she hasn’t been pushing it. For Lucinda enjoying the process is key, she likes having builders around and has no particular need for the house to be finished quickly.
Sometimes the most sustainable approach requires a bit more thought and effort
Access was a key constraint when considering how to build the house. Not only do they have the slope to contend with but there isn’t vehicle access to the top of the site where the new house is situated, so the last 20-25 metres is a footpath. Part of this is about preserving the trees on site. This meant that using big machinery, such as a crane, was not going to be possible. Some elements of the house have been pre-fabricated off site, including panels and all components for the roof.
The foundations minimise the use of concrete
Rather than having to excavate and put a concrete slab down for the foundations Lucinda used concrete canvas. It’s a fabric impregnated with cement which is about 8mm thick, and you roll it out like a carpet and spray it with water. It sets hard and then the building is suspended above it. Lucinda tells us there is only a small amount of concrete in the building, about three and a half cubic metres altogether. The building sits on concrete columns, octagonal shaped as that was the easiest thing to build with a shuttering ply. The columns are different depths, according to what they found as they dug the holes. They are reinforced and then there are two steels, after that, everything is timber, at between 200mm and 800mm off the ground, as the sub level follows the slope.
Timber is used in an efficient way
The structure of the house is timber portal frames, with a rigid frame made of timber columns and beams that support the roof and walls. The frame transfers the structure’s weight to the foundations, which allows for large spans without internal ties, giving an open space within. The individual frames are fixed together with plywood gussets which are connected by the racking board, which is OSB on the outside and Smartply on the inside. The Smartply gives it a continuous airtightness layer on the inside, which makes for a simple structure. Lots of taping is needed, but it is a relatively straightforward way of creating robust airtightness layer, rather than a loose membrane which could get damaged.
Check out another timber project in The Hub. This Buckinghamshire Passivhaus, a PH15 build.
Lucinda saved money by doing a lot herself
The builders delivered an airtight shell for Lucinda to fit-out herself. At the point of the handover they had battened externally, ready for the cedar shingles to go on. Lucinda had always envisaged putting on the shingles by herself, but hadn’t thought there would be 10,500 of them and how awkward the job would be. So she got her builders back to help with some sections.
As she didn’t have scaffolding she was extremely fortunate to enlist the help of a relative, who is not only an architect but a rock climber! Lucinda explains how he rigged up ropes and dangled off a harness for a month putting the shingles on the upper rows.
As project manager Lucinda has worked closely with her plumbers and electricians to understand how everything works and to make sure she is doing things in the most logical and efficient way.
The timing of the build didn’t help her budget
Lucinda began with a rough ‘pounds per square metre’ cost and looked at the cost of other people’s builds so she could pitch where she wanted to be. However, she was not fortunate in her timing as timber prices pretty much doubled over the first year of construction. That made a huge difference and required her to make some modifications. For example, the price for standard Canadian tapered shingles was about £60- £65 a bundle when she started. She needed around 120 bundles and by the time she came to the order them, they had gone up to £155 pounds a bundle, so they had nearly tripled. This just wasn’t going to be possible within the budget, so she ended up using UK grown shingles, which in fact were grown a few miles from her site and then processed in Shropshire. She hadn’t even thought of doing it that way but it fitted with the ethos of the build much better. They may not be quite as long lasting and look different to what she had expected, but Lucinda is still pleased with her decision.
Don’t be afraid to work in your own way
Asked about what she’s learnt through the process Lucinda confesses that she knew you shouldn’t alter the designs once the build has started. However, as the project progressed she realised she wanted more double height space area internally. Of course there were ramifications but it was still something she wanted to do.
Similarly when project managing, she feels she could have lined up the tradespeople further in advance. For example she tended to wait until she was ready for an electrician before finding one, and then had to wait because they are all booked up. While this would move things along more quickly she feels more in control doing one step at a time rather than trying to manage five trades at once.
Determination will see her complete the project
Whilst the house may look near completion, Lucinda is still working through a list of tasks. Last month it was getting ready for the airtightness test, making sure that the taping was complete and protected where necessary. She’s also been working out details for the staircase and designing the kitchen, which she reckons she is overcomplicating, but she can’t help herself!
On the construction side, she’s putting in extra batons before the plasterboard goes on, ready for fixing things later. She’s also waiting for people to do various tasks, the plumber to move a couple of pipes, the electrician to bring in the last cables, etc. She needs a little bit more wood chip to finish the paths in the garden and for the drainage system. The next big thing is plasterboarding and plastering.
Using an ‘eco plasterboard’ could lower emissions from the fit out
When it comes to the most carbon intense areas internally plasterboard and plastering are significant. Lucinda had hoped to use a low carbon alternative plasterboard from Adaptavate, but it is not yet available commercially. The company already make a lime-based plaster Breathaplasta which can be applied on top in much the same way as a gypsum plaster.
A house build can be a labour of love
Lucinda just does a little bit each day. Perhaps more is achieved on some days than others but it’s an enjoyable process, even if a little exhausting at times.
Ideally, she doesn’t want to move in until it’s completely finished, because she thinks that gives her the drive to keep going. Once you’ve moved in you never finish things!
As for when she might move in, her children think it’s not about living there at all, but about making it and she will keep going for as long as possible.
Clare and Ross Booth from Coldwells Build share details of their prefabricated, turnkey Passivhaus designs that aim to simplify the delivery of high performance homes in Scotland.
Interview with Clare and Ross Booth
Ross and Clare Booth are the founders and directors of Coldwells Build in Aberdeenshire, Scotland. Ross started out as a joiner and construction worker while Clare has a background in journalism and communication. Their construction company has delivered a number of bespoke housing projects and is now launching a range of contemporary, turnkey Passivhaus designs which will be sold at a fixed price and prefabricated off site.
This episode is set against a backdrop of potential change to the building regulations in Scotland.
Help keep the Scottish Passivhaus equivalent on track
Last year the Scottish Government announced plans to introduce new regulations for all new build housing to meet a ‘Scottish equivalent to the Passivhaus standard’.
Whilst this was exciting, the devil is in the detail and this is currently being fleshed out in a consultation about the proposal. Unfortunately there are signs that it may be watered down, which means we need to have our say and get it back on track. So please take the time to respond. The Passivhaus Trust has made it easy to understand what detail is lacking, so check out their guidance to help you play your part in the consultation.
The ‘Passivhaus equivalent’ doesn’t need to reinvent the wheel
The Passivhaus standard works so well because it is a holistic approach which addresses building physics, and there are quality assurance processes built in so that we get the results we anticipate.
Clare says that adopting the Scottish equivalent to the Passivhaus standard could have a profound effect on future homes across Scotland, and help the Government reach its net zero emissions target set for 2045.
Upskilling the workforce is essential
Clare and Ross believe that for Scotland to achieve higher building standards there is a great need to provide additional training for construction workers. Ross shares an example from his own experience as a joiner when he installed an airtightness membrane but didn’t really understand what it was doing or the attention to detail required when carrying out this work.
Clare and Ross have both upskilled as part of their professional development
While networking Clare discovered that some free Passivhaus tradesperson training was available and sent the whole team to Glasgow to attend. Ross admits that he was sceptical at first but was completely converted by the end of the training. This was Government funded and provided by BEST (Built Environment Smarter Transformation) who are working to decarbonise the built environment through upskilling and educating people in the construction industry.
Clare also attended a number of satellite events at the COP26 global climate change summit in 2021. Amongst her findings was that most homes still rely on oil and gas for heating which is contributing to nearly a fifth of the UK’s carbon emissions, the UK has some of the worst insulated housing stock across Europe, and that the performance gap currently sits at a staggering 60% in some cases.
A ‘bespoke’ home project is not a simple process
Having worked with numerous clients on one-off bespoke projects, Clare and Ross have identified key pain-points in the self build journey. For example, it can be difficult to design projects within budget and so clients need to go back and forth between their designer and the construction team until they have refined plans. There’s also fatigue from the estimated 3000 decisions that are needed to realise a new home. Then add in the unpredictability of the build itself, which may be subject to bad weather delays and noise complaints from neighbours.
Building off-site in a workshop is a lot more predictable
In an attempt to address some of the challenges of self build and streamline the process for their clients Clare and Ross decided to create a collection of predesigned homes that they would sell for a fixed price. Not only would these be beautiful contemporary homes but there would be a set number of materials and colour choices, making it easier for clients to choose. Another big change would be taking advantage of modern methods of construction by prefabricating these houses off site in a workshop. This also has the potential to increase quality as everyone can be trained in specific roles.
By increasing the insulation specification, their Passivhaus designs can work anywhere in Scotland
Over the last two and a half years Ross and Clare have been working with John Gilbert Architects to produce six ready-to-go Passivhaus designs.
As Passivhaus is site specific one challenge they faced was how a standard design could work on any site. The solution was to over-egg the insulation slightly so that the solar gains were not as critical.
We’ve got quite a chunky wall and roof system. And we’ve tested the house on PHPP on a coastal exposed site in the North East of Scotland, and we’ve tried it in every orientation, and it’s passed.
A visualisation of one of the ready-to-go Passivhaus designs
A building plot is essential to start the process
Although you might be tempted by the designs you need to have secured a building plot before you can engage with Coldwells Build. After selecting a house design they will check that it works for your budget, before moving on to a concept agreement.
At this point it is possible to make a few internal layout changes, providing that they don’t lead to structural changes. The team will then prepare a site plan and get everything cost checked and prepared for planning permission.
Once planning has been approved, Coldwells Build will create a preliminary building agreement and you can start looking at the internal finishes and kitchen designs. They will get the cost as accurate as possible at this stage and then the architect will submit for a building warrant. Once this has been approved, the client can sign a building contract, and the prefabrication will begin.
Assembly ‘on site’ will take a matter of days
Ross says that prefabricating the home would start within three months of having a building contract signed. Whilst the prefabrication is happening, the groundworks team can be on site, preparing the foundations, substructure and floor slab. Once the timber frame is delivered to site, it can be made wind, water and airtight within days. The cladding will be pre-installed and the wall panels and roof panels pre-insulated. The airtightness membranes will be pre-fitted, and only the joints will need to be taped on site. It is a quick turnaround from arriving on site.
The costs will be fixed and known upfront
Clare says that the average price for their four-bedroom turnkey design will be around £420,000. There is also a ‘You Build’ option, which gives you a completed shell that you would then have to fit out, and this is currently around £220,000. Again this is for a certified Passivhaus, which is core to their offering.
The Passivhaus collection will be launched next month but there is already a lot of interest and they even have a waiting list! So it’s an exciting time for Coldwells Build. They are currently working with their first customer which they will use as a test run and to check all their processes, before taking on more customers. Initially they are going to be limiting themselves to producing six houses per year. Clare explains that the most important thing is not to overload themselves and therefore ensure the quality of their homes.
Architect Josh Wood gives us an insight into his own self build project, where the balance between keeping costs low and creating a sustainable home have pushed him to come up with creative solutions. By undergoing most of the work themselves, Josh and his partner Amy have been able to transform their snug, back garden plot, into a comfortable and energy-efficient home. Josh explains how thinking outside of the box may be an excellent option if you are looking to get on to the property ladder with a smaller budget.
Interview with Josh Wood
Bristol based architect and founder of Green Trace Architect, Josh Wood joins us today to explore the topic of low cost sustainable homes. Josh is a qualified Passivhaus designer, with a background in environmental engineering and he specialises in sustainable architecture and creative design. Along with his Partner Amy and a handful of friends, Josh has undertaken quite a feat in building his own sustainable home in Bristol on a modest budget. In this chat, Josh talks us through his experience in working with clients, building his own tiny house and now his own self build, highlighting the key lessons that he has learnt along the way.
Join The Hub to access our in-depth video case study of Buckinghamshire Passivhaus, a PH15 build
Tiny houses can help you identify how you want to live
The tiny house revolution is one we have seen grow over the past few years and in this chat Josh talks of his own experience living in a tiny house he built himself. Tiny houses can be a great option when you have a thirst for building but are on a small budget or wish to escape the expensive private rental market. Tiny houses can offer a wonderful starting point to experiment with different design ideas and learn a range of skills whilst working on a small scale. In limiting yourself to live in such a small space, you can analyse just how you want to interact with your home and identify what you maybe took for granted in the past. Josh talks of how the size restriction challenges you to use space incredibly efficiently and pushes you to live a lot of your life outside. This experience helped Josh make connections through the Bristol Tiny House Community and overall he learnt a lot about how he needed his home to perform for him.
See opportunities where others don’t
Many people view small and oddly shaped plots as too difficult to work with, which means they are often dismissed at the beginning of the search for land. Josh explains that to afford this project in the heart of Bristol, he knew they would need to think creatively when looking for a plot. His search mostly consisted of these often overlooked sites and instead of viewing them as restricting, he saw their limitations as the framework of an exciting design challenge. There is a wealth of quirky plots across the country that many people overlook, but it may just be your ticket onto the property ladder if you are willing to think creatively.
“I’d been searching for land and I was always keen on buying a piece of land that everybody else thought was just useless.”
A failed planning application attached to a site is not always a sign to run the other way
When Josh initially found their site, the vendor had applied for planning permission but had failed to get it approved. Normally, these applications are then withdrawn from the planning website, but in this case they were not. This was very fortunate, and Josh took the comments from this failed application as a checklist that he would need to meet in his design. This is another instance where if you are willing to think creatively, what may originally seem like barriers can become guidelines.
A planning pre-app can help reduce the risk
Josh highlights that a pre-application to the planning authority can be an excellent option when considering an unconventional plot as it allows you assess the likelihood of success before you undergo the full planning process. Pre-applications are also closed to the public, so Josh was able to find out if their planning was likely to be approved before they had finalised the sale and without it affecting the price of the land. Pre-apps can also raise anything you may have missed or any concerns that the planning authority might have, so you can be pretty certain that your official application will be passed when the time comes. As a result of undertaking the pre-app process, Josh was able to submit their planning application within 21 days of the land being theirs and were granted planning not long after.
Small sites can dictate the design and construction methods
The site for Josh’s build had been parcelled off from a back garden and is located away from the road via a public alley. The site is therefore classified as a back land development which posed a few challenges for the build in terms of access and did dictate a few of the decisions surrounding construction methods. For example, Josh knew from the start that a prefabricated shell would be out of the question due to their limited access. In addition, the width of the standard timber they chose, based on price and accessibility, for their framing limited their insulation to 200 mil. Furthermore, the placement of the site meant that the design had to consider privacy and how to avoid overlooking or overshadowing the neighbouring properties. As a result, the best way to achieve all these goals was with a roof pitch of 25 degrees and to construct right up against another building, leaving a very small 400mil gap to work with. This gap was just enough space to fit scaffolding with a one plank width, so quite a squeeze when fitting the weather defence and siniat boards. All of these constraints can seem a bit overwhelming at first, but Josh’s overarching message highlights that by changing your mindset to view theses restrictions as exciting challenges, will lead to a unique and interesting design that you may not have thought up without them there.
Being both architect and builder can give you greater understanding of each role
The architect-builder relationship is a very important aspect in any project, and Josh highlights that after experiencing the role of the builder, he is better equipped as an architect to relay his designs and communicate with builders on future projects. He has even found the perfect balance between too much and too little detail on his drawings, as to provide a solid outline without restricting a builders need to potentially improvise on site.
“As an architect, you often have to go to sites and have conversations with builders and have conversations with clients, and to actually experience what both of those go through is invaluable as an architect.”
“I also think the age old question for architects is how much to draw and how much not to draw… if you try and draw too much, you’re likely to get it wrong, a builder sometimes knows best. So I found I would draw this in the exact detail, I’ll come to site and go nah that’s just not going to work, actually. So you need to draw the intention and give an indication of what’s required… but as soon as I start to put too much detail in there, it actually becomes less useful.”
Cost vs sustainability
This project began with the premise that it needed to be both a low cost, energy efficient and sustainable home, but this is often a tricky thing to balance. Josh has managed to keep the cost down by doing the majority of the construction himself, allowing him to spend the budget on good quality materials rather than labour. Also, by choosing to use a simple timber frame that could be sourced from local building merchants, constructing his own insulated raft and choosing wood fibre insulation meant that the design embraced simplicity in order to maintain sustainability. Windows are usually quite an expensive part of a build and Josh opted for triple glazed UPVC windows with a U value of 0.78 as they were a third of the price of composite windows. These windows are a great option if you are looking to get a good performance for a lower price, but Josh does also acknowledge that it was a difficult decision as the materials are not the most ecologically sound. This circles us back to our common theme of embodied carbon vs energy efficiency and especially in builds with a smaller budget it is sometimes necessary to make these compromises.
Some building regulations may be waived if there is enough reasonable evidence
In some instances you may achieve planning permission but be unable to actually build your project due to conflicting building regulations, in Josh’s case, drainage almost posed this issue. Because the site is small and located in an urban setting there were concerns about surface water drainage; where would the rainwater go? After carrying out an assessment, Josh put in a request to have the drain feed into the main sewer like the other buildings surrounding the site. However, with the current state of sewage and water disposal in this country, the council is very unlikely to let any new build drain surface water into the sewer, so his request was denied. Fortunately, after undergoing testing on the sites soil, it became evident that a soakaway would be a possibility and was recommended by planning and their site engineer. This was an interesting situation as the soakaway would actually be too close to the building to pass building regulations, but as the advice from the authorities had suggested this solution, this detail was waived for the project.
When do you need paid help?
Josh and his partner Amy have undertaken the majority of the construction themselves, but there were a few areas where they needed help. Josh enlisted some friends and some paid labour when it came to laying the groundwork and the concrete slab, as well has some additional help whilst assembling the structure and getting the glulam beams in place. Josh did choose to enlist some professional help for the render, as lime render is not commonly used in this country and it is very important to ensure it is done by someone who really knows how to work with the material. With that being said, the rest of the work has been done by Josh and Amy and shows that it is possible to keep costs down by reducing the need for paid labour.
Of course, there are limits to this and sometimes paying for a professional service also gives you peace of mind. Josh explains that he chose to make the insulation raft for the foundations of the house himself rather than opting to use a system like Isoquick but wouldn’t necessarily recommend this. The risk with a foam raft is that if it breaks whilst the concrete slab is being poured, you end up with a big concrete mess. Fortunately, Josh’s stayed intact and he was able to save £5000 by taking on this challenge, but the stress of the process might make him reconsider the decision in the future. Ultimately, it depends on the risks that you are willing to take and the hands on work you want to put into the build, but Josh provides an excellent example of how these creative risks and out of the box solutions can lead to a wonderful home.
What not to compromise on in a low cost build
Building a sustainable and well insulated home were priorities from the beginning, but Josh has ended up improving the spec on a lot of the materials/insulation and included an MVHR system which was not on the original design. This is quite common in these projects because as it progresses you realise you will only undergo this process once and you want to get things to as high a standard and performance level as you can. Things like airtightness and MVHR systems are not ideal areas to compromise on as they are pivotal factors in the overall performance of the house.
“The initial plan was not to have any of that because we thought we wouldn’t have the money. But as we’ve gone on, we actually shoehorned in the MVHR because I thought we can’t not have an airtight home, and if we’ve got an airtight home, we need the MVHR.”
“But with these things, you will keep on working, you’ll get more money, and it will come and then you’ll wish, I wish I put it in. So we’ve kind of gone on that basis.”
How well does the house perform?
After Josh’s calculations using the Passivhaus Planning Package, the house meets the Passivhaus requirements for airtightness, but just slightly falls down on the level of insulation needed to get full passivhaus certification. However, it does meet AECB building standards and has excellent performance, especially considering the limitations that they were faced with. Using sustainable and breathable materials such as the wood fibre insulation also help to maintain the overall health of the structure and will create that overall pleasant environment that Passivhaus is known for.
Internal finishes can be a great place to save money
Josh and Amy are still working on the internal finishes of the house but have already managed to make use of a lot of reclaimed materials. They have created a beautiful balustrade out of old gates and plan to construct their kitchen out of second-hand filing cabinets. Using reclaimed elements, especially in your finishes, not only allows you to save money but also think about materials more creatively and bring some wonderful character to your home. Josh also opted to use a company called Stair Box who provide flat pack staircases. Whilst this was a bit of a puzzle to assemble, it is an interesting solution when trying to work within a low budget.
Slow down and try and enjoy the ride
One of Josh’s pieces of advice was to slow down because things take as long as they take. In trying to rush things, we often make mistakes, do a bad job or end up having to do it all again. It is important to remember to slow down and consider each stage so you can be sure you are doing it the right way, and you might even enjoy the process more too!
“I think I now understand the tale of the hare and the tortoise. Because I never really understood that as a kid, where’s the moral in that? And I think now it makes sense to me as a builder, you’ve really got to plod not run. Architects may be working at such high pace sometimes that can’t be good for either you or the project. I feel that I’ve learned to take things slowly and that’s been actually more beneficial to doing the project efficiently”
Take risks, think creatively, and keep searching for that perfect piece of land!
Overall, Josh’s message is that you can achieve a sustainable and high performing home on a small budget. By seeing potential in the things that others may overlook and taking risks, a self-build project can be an excellent way to get on the housing ladder.
“My advice, I suppose, would be to keep looking for those small bits of land and be very creative about how you might be able to make that into something!”
Martin Twamley from Steico explains how to use breathable internal insulation, while avoiding the risks of condensation and mould.
Interview with Martin Twamley
Martin Twamley is Technical Director of Steico UK. Steico have been producing timber-based materials, predominantly structural timber and insulation materials, since the 1960s and selling them across Europe. Using only pine and spruce they make a number of different products, and will always provide guidance as to what the correct product would be for the required application.
“Once people start using timber and understanding it, it’s a sort of material that you fall in love with, and you then change your building process.”
The products have low embodied energy
Structural products like I-joists were first used in the USA and the motivation was that it was the most sensible use of the raw material. However, as a natural material and one that goes through little processing it also has a low embodied energy, and will even lock up carbon.
Laminating the veneers strengthens the product
The I-joists are created from Laminated Veneer Lumber. They are made by peeling a tree, creating 3mm veneers, and then bonding them back together. This means that individual weaknesses are removed and spread across the whole product. The strength-to-weight ratio on engineered timber is then much greater than it is for solid section timber as you’re getting a much stronger product for less raw material.
There is very little manufacturing waste
Martin explains that the good thing about producing both structural and insulation products is that there is very little waste. For the structural timber they use the de-barking and peeling process. For the insulation materials they use chipping and milling. Therefore, what they can’t use for the structural timber they can use for the insulation. What they can’t use for the insulation they can use for producing their own pallets. And if they can’t use it for pallets they have a biomass power station where they can use it for electricity generation.
UK housing stock has a need for internal insulation
The UK housing stock is some of the oldest in Europe and is in desperate need of retrofitting. With a reluctance to insulate externally and change the appearance of this historic solid wall housing, internal insulation may be a better solution.
The traditional way of doing this is with systems that try to block the moisture, rather than being able to control it. When you try to block moisture there can be an issue with getting it trapped inside the building instead. This potentially adds risk to the fabric of the building, because of mould and condensation problems.
The Steico wood fibre internal insulation system allows water vapour in, controls it, holds it, and then lets it out again.
Standard insulation installations are vapour closed
These typically are the foil-backed polyurethane type materials that are either on a frame system or dot and dabbed onto brickwork. In theory they don’t let any moisture in, which is a good thing for the fabric. This can however lead to high moisture levels internally, so you might need to consider an MVHR for example. Mould will happen when warm air gets behind the plaster board and hits the cold wall surface. It might not even be until years later that the mould shows itself on the internal surface.
“When people think about air quality, they generally think about external air, but we spend 90% of our time indoors. It’s the internal air that we’re breathing. So that’s what’s impacting our health.”
These are the kinds of systems that tradespeople and DIYers are most likely to use, because they’re readily available. Also, homeowners are primarily just thinking about thermal performance in the winter. But actually, when you consider a holistic approach that takes into account all the possible issues, the material choice is incredibly important.
Internal insulation doesn’t have to significantly impact on the room size
Martin talks about applying a thin layer, typically an optimum amount of 40-60mm. Even in relatively small rooms that’s an amount that won’t really be noticed.
What works for one building, won’t work for every building
What works for one elevation of a building might not even work for a different elevation of the same building, because of different weathering exposure. This is why it is so important to have an assessment done, particularly if you’re looking for a really low U-value. Martin explains that generally speaking a 40mm or 60mm board on standard brick will work in the majority of situations.
Take the wall system back to bare brickwork if possible
The wall system should be as breathable as possible. That means that you don’t want anything on the internal side that hinders water vapour movement, such as impermeable layers, cement-based plasters and renders, and paint layers.
The external face is also important to consider (such as renders and re-pointing), because this is where the majority of the water is coming from.
With this natural, breathable approach, there is a full bonding layer (typically a lime based product) between the insulation and the wall. This is in contrast to a traditional approach that would have a cavity. The fact that there is no cavity means that there is no collection of liquid water, which is what leads to mould and condensation issues. Instead, any moisture is either passed onto the brickwork and out the front, or it can go back to the inside.
Pay particular attention to the critical areas
Window reveals are particularly important. If you have a warm wall surface, then the window reveal will be the coldest area. If you don’t insulate into that reveal then that is where all your condensation will form. Martin suggests that with a 40mm or 60mm on the wall, a 20mm board on the reveal will be fine.
Another critical area that could be overlooked if somebody is insulating ground and first floor, is the void where the floor joists connect into the wall. These can be cold spots where condensation will be much more of an issue than it was before. To prevent this, you can tape around the junction of the joists to the existing wall. This stops the route for convected airflow into the wall.
Where you have internal walls connecting with external walls can also be problem areas. If you’re insulating the external wall, then the corner of that internal junction can be quite cold. Steico make a wedge-type product of thinner insulation that can go into the corner to stop the condensation risk.
There are useful resources available
Martin makes reference to The Guide for Sustainable Renovation, by The Pebble Trust, as being a valuable resource for anyone taking on a retrofit project. It gives advice with a holistic approach that considers all of the moisture risks involved.
The carbon storage element of materials is often overlooked
A frustration for Martin is that in the UK he thinks we tend to be quite product agnostic. It is very much that if you achieve a certain performance level then it doesn’t matter what you use to to get there. He compares this with Bavaria, Germany, that has a new system brought in by local government. They are offering a 500 Euro grant for every cubic metre of biogenic carbon locked up within the fabric of the building. In the UK we have U-value targets, but nothing that looks at the amount of carbon stored within the fabric, or the type of material that is used.
