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.
Mike Eliason talks about his book, Building for People, and the massive opportunity we have to create better places through being more intentional and thoughtful.
A year working in Germany laid a foundation for Mike’s career
Based in Freiburg, Mike was part of a wide variety of projects: detached houses, multi-family housing, some public work, some laboratory work. He lived in a suburb that was heavily pedestrianised, and which he describes as, “the quietest place I’ve ever lived.” And he got to know the districts of Vauban and Rieselfeld, where self-build, multi-family housing, Passivhaus and mass timber construction were all present.
The concept of Baugruppen (“group build”; involving residents in decisions to foster community) was also well underway. Even though Mike was not absorbing these ideas fully, he felt a desire to take them back to the USA. Many of those memories have come to the forefront for him in the years since – and the ideas are finally starting to become more mainstream, two decades after he was first exposed to them.
New development needs a rethink to shift its priorities
Mike’s work started by advocating for better multi-family housing, similar to what he found in Germany. That connected him with a broad network of advocates and politicians who want to achieve better housing and public developments. But they don’t have resources they can show to elected officials and say, “This is how things can be different.”
The book aims to ‘formalise’ what good looks like, and support advocacy work by adding to the broader discussion of how development in the USA needs a fundamental rethink to prioritise public health, community, affordability and sustainability.
He sees the problem playing out in Seattle, where transit infrastructure is being redeveloped without open space, without affordable housing, and without features to mitigate the urban heat island effect or deal with storm deluges.
Housing in the USA is not fit for purpose
There is little variation in housing, with no real breadth of options between townhouses and large multi-family apartment buildings. Compared to the rest of the world, Mike describes the USA and Canada as “an anomaly” in this regard.
He believes that often it’s like living in a hotel: corridors down the middle of large buildings, with units either side. The units are really deep with a window at only one end (“like living in a bowling alley”), unless you’re fortunate and live on a corner. The buildings are not climate adaptive – there’s no opportunity for cross-ventilation, and solar protection is not a common feature.
The units tend to be large, which makes them unaffordable, but with only enough space to fit two bedrooms. If the designs tried to accommodate a third bedroom, it would have no window. “Really, they’re designed for roommates rather than families,” says Mike.
Floor plan for Larix, a proposed six story Point Access Block, allowing for family-sized homes, units that cross ventilate, and bedrooms positioned on the quiet side of the building (Credit: Michael Eliason/Larch Lab)
Achieving better outcomes starts with a better vocabulary
Mike describes the lexicon that people have for talking about housing and buildings in the USA as “stunted.” Feedback about his book often centres on how it has opened the reader’s eyes to certain concepts, which he attributes to expanding the vocabulary people can draw on in those conversations.
In structuring the book, Mike pulled together concepts he was already researching and writing about, in a way that tried to make sense of them all. That led him to including topics like low carbon housing, eco district design, human centred places, and nature and open space.
Proving concepts can start with a single home
While the aspiration is to apply the concepts to large developments and entire districts, they can be just as readily pulled together in a single development – even just one house.
Development in the USA is antithetical to outcomes like being community-oriented, being adaptable and climate resilient, and providing comfort and protection. While that remains the case, it’s important to highlight the differences compared to European housing as a way to explain why the outcomes are so different.
Passivhaus and mass timber have demonstrated that change can happen
People in North America talked about Passivhaus for years. But until there was a tangible project to use as an example for politicians, architects and developers, it was hard to show why it was better than the status quo. Mike has experienced the same with mass timber, for which he is a big advocate. Now mass timber projects have been constructed, others can see and feel the difference.
Freiburg’s car-light Vauban ecodistrict is filled with numerous Baugruppen (photo credit: Payton Chung)
Ecology, affordability and community are at the heart of eco districts
The concept of an eco district is about developing places where people can live a low carbon lifestyle and thrive. Often, they are developed on brownfield sites (Vauban was a former military base, for example).
At its simplest, an eco district is a place where you don’t need to drive to accomplish daily tasks – they are walkable and bikeable, with low-traffic streets. They prioritise green and open space, there is more opportunity for community, and they are low stress. “Imagine an entire neighbourhood that isn’t prioritising the car?” says Mike. “It doesn’t really exist in much of the USA.”
Another common feature is a higher level of affordability, to create a good social and economic mix. In the USA, there are token affordable housing projects but it is mostly market-rate housing.
US arterials and highways are the types of streets where dense affordable housing is legal (photo credit: Michael Eliason)
Planning around cars is not conducive to people-friendly places
Often, developers in North American cities will just build parking because they think it’s what the market requires. Even transit-oriented development contributes to the problem. Districts then become very car-centric, and public health, open space, nature and community are not priorities.
There is some connection between reducing the number of cars and enabling places to be a little better, but it’s quite a ‘chicken and egg’ scenario. Mike feels it needs a developer to say they want to do a district with no cars, then prove that the model for a car-light place is possible.
One developer in the USA, Culdesac, is building multi-family developments that don’t require parking. Instead, they provide spaces for the community to walk in – pedestrianised streets or alleys, places where cafes can spill out, where community events can be held, or you can just run into your neighbours. It’s harkening back to a way of life before cars became the overwhelming mode of transportation.
Creativity should be at the heart of regulations
Regulations can either be written more creatively, so they permit or incentivise new ideas rather than block them. Or they can be written in a way that encourages people to respond to them more creatively. Mike sees this creativity as essential.
“If we’re just pumping out the same thing over and over again … okay, we know how to do it, and we can maybe do it well, but it might not be the right thing for somebody else. We need places that offer more variability.”
In the USA, for example, most cities have residential zoning that only allows detached houses. Multi-family housing is impossible, because it’s illegal! By contrast, Brussels has a regulation requiring Passivhaus, and provided incentives and support before the requirement became effective. And France has a 50% bio materials mandate for new construction, which is driving more straw panel and mass timber buildings.
There are so many solutions to improving housing affordability
The Netherlands does small districts of self-build housing with around 15 to 30 lots. The cost of infrastructure and management is lower because they’re paying the city rather than a developer, and the city is not seeking a profit. The houses are all designed and built by different people and, in Mike’s words, “the neighbourhoods are amazing. They’re incredible. We should be doing more of that in the USA.”
The Baugruppen model is a hybrid between market-rate development and cooperatives or even social housing.
Mike is a fan of cooperatives, especially the Swiss model for them. It uses a cost-based rent that has created some of “the most fascinating and innovative housing” that he has ever seen.
The Mietshäuser Syndikat – the rental house syndicate – came out of Freiburg while Mike was living there. An umbrella organisation effectively co-buys multi-family property with the tenants and owns it in common. The building then can’t be sold without everyone coming to an agreement, because it’s a 51/49 ownership split. Everything is managed by the residents, who contribute to a solidarity fund to help grow the organisation and help other entities develop projects.
However, the lack of variability in the USA – with very little public housing, cohousing or cooperatives – means it’s going to take a lot of support to grow that ecosystem.
Operable exterior shutters prevent unwanted solar gain in summer, and provide additional privacy year round (photo credit: Michael Eliason)
Housing that responds to climate change is essential
Understanding the impacts of a changing climate is essential. How do we deal with the sun and overheating? Wildfires and smoke? Rain and floods. For this reason, Passivhaus is the starting point for any project that Mike works on. He loves Passivhaus because it’s comfortable and balances high tech and low tech. If you need heating or cooling, it’s the smallest amount possible.
Gaskets and tape help to keep out cold drafts, moisture, and wildfire smoke. (Photo credit: 475 High Performance Building Supply)
More rain will lead to more mould in properties, and Passivhaus de-risks mould to a greater extent. In extremes of heat and cold when you lose power and can’t run cooling or heating systems, Passivhaus increases survivability. Mike cites studies in the USA where buildings designed to the minimum standard of regulations were only habitable in a deep freeze situation for half a day at most. After that, pipes started to burst. Whereas a Passivhaus was relatively warm and habitable for several days.
The climate is an issue whether you live in a bespoke, detached house, or a multi-family building. All of these things are going to affect people, so understanding the most optimal ways to adapt or mitigate the effects is really crucial.
A people-first street in Vienna’s Seestadt (photo credit: Lukasz Karnas)
Better housing can also help to address social isolation
The IPCC has previously talked about the benefits of cohousing and other forms of community-oriented housing. It’s not just that you know everybody in your building, though that day-to-day social connection is important. If you’re also designing a building together then you have similar values and things that you’re prioritising.
There’s a fundamental difference between developing huge, anonymous buildings with 200 or 300 units and smaller buildings. It’s easier to know people and easier to ensure that people are okay if there’s a climate event. Many people who died in the heat dome event in the Pacific Northwest were elderly residents who didn’t have a social network, who didn’t have people who could check on them.
We don’t need to reinvent the future
We already have what we need to create better places. Active solar protection, Passivhaus buildings, low carbon construction all exist in the world. Mike’s message is that, “we can use our imagination to reconfigure them to the condition, spaces or places that we would like, but we don’t have to reinvent the wheel. Everything that we need to build low carbon places already exists. We just have to really prioritise them.”
There’s a huge network of people who already know how to do so many of these things, who talk about different ways of building and living. Finding ways to tap into each other’s knowledge and experience is crucial. Then, we can start to change the status quo bias, and the attitude of, ‘things have been this way forever, so why change it?’ By spreading the knowledge about what is possible, we can provide shelter that is moderately affordable, so that, as a society, we can stay connected and stay in the community.
Tilmann Kramolisch from natureplus explains why their eco label was established, how materials and products are assessed, and what it means to use a natureplus certified product on your project.
Interview with Tilmann Kramolisch
Tilmann Kramolisch is the Managing Director at natureplus, a non profit eco label that aims to provide transparency and clarity to the consumer within the construction sector. The natureplus accreditation measures the impact of different building products on the environment and human health, to ensure that any product with a natureplus label is certified as healthy and sustainable. In this chat, Tilmann talks us through the natureplus accreditation process as well as highlighting some key differences to be aware of in other eco labels.
Healthy building products don’t harm the natural world or human health
The natureplus eco label certifies that building products are not harmful to the environment or human health. The World Health Organisation (WTO) has classified a condition called sick building syndrome, which refers to the negative impacts that a building can have on an occupant’s health. Leading causes of sick building syndrome are damp/mould issues, poor ventilation and toxic emissions from materials or the environment. Many natural building materials are proven to tackle these issues and by reducing the use of harmful chemicals/pollutants, the environmental and human health risks are significantly lower.
Materials are not the same as building products
Tilmann makes a key distinction between building materials and building products. Materials refer to a substance that can be made into many different things depending on how it is treated or used, whereas a building product refers to one of the outputs. Tilmann uses clay as an example of a building material, that can be used to make the building products of plaster or bricks. Natureplus measure the sustainability of building products on the market.
The natureplus eco label takes a holistic approach
Tilmann explains that the natureplus certification rests on three core pillars:
Health
Climate protection
Sustainable resourcing
For a product to be classed as a healthy product and receive natureplus accreditation, it must consider all three of these in all aspects of its usage and existence.
Asbestos is a good example of a product that would have failed the natureplus accreditation. It was originally considered a great material with many positive attributes. However, we now know how harmful it is to our health and when a building is deconstructed this material must be carefully removed and disposed of. This therefore negates the previous intention of saving resources as it cannot be reused. So if you begin with the three pillars approach when creating a new building product, you are mitigating any of these risks before it is widely available for use.
“When you develop a material or plant material, it’s very important that you apply all three. So healthy accommodation, climate protection and sustainable resourcing.”
A supply of cork
Golden rule: When it comes to fossil fuels, leave it in the ground
The natureplus label requires a product to be composed of at least 85% bio-based mineral materials or recycled materials. This is to exclude products that are primarily petrochemical based and ensures that the products aren’t damaging the environment or human health.
The process utilises independent testing to ensure transparency and quality
The Nature Plus Association (NPA) is the non-profit responsible for issuing the eco label. However, the assessment of the building product is carried out by a cooperative called the Nature Plus Institute (NPI). So the NPA sets the criteria and the actual testing is undertaken by the NPI.
Tilmann recommends taking a closer look at which companies are issuing eco labels and check the transparency of their process. In the case of natureplus, the assessment is carried out by an independent body to ensure transparency and quality assurance.
To test the climate impact of a product, a lifecycle assessment is performed. This looks at the A1, A2 and A3 stages of the building product, which refers to the upfront carbon emissions: from cradle to gate.
When it comes to assessing the health impacts of a building product, there are two areas that need to be assessed: what material does the product contain and what comes out of the product? For example, the Eco Institute in Cologne will test the product for substances such as formaldehyde or Volatile Organic Compounds (VOCs). They will then put a sample into an airtight chamber and measure the emissions from the product over a 28 day period. In order to meet the natureplus standards, the product must not exceed very strict thresholds.
Quality control is assured through the natureplus guidelines
natureplus have strict testing standards which are replicated in a variety of different laboratories and testing sites. By having set standards and a precise criteria, the results can be guaranteed to be accurate and consistent.
An Environmental Product Declaration (EPD) does not necessarily mean it is sustainable
Unlike the natureplus eco label, an Environmental Product Declaration (EPD) just quantifies the environmental impact of a product and does not indicate whether these are positive or negative. The label in itself is therefore not a signifier of quality or sustainability and instead offers transparency. This is very much needed in the construction industry but does require further research to determine if the product is good or bad. The natureplus eco label instead tries to communicate quickly and clearly that this is a product you can trust to have a focus on health, climate protection and sustainable resourcing.
“Communication is key and what we try to do is do it as simple as possible. So this is why we do this very, very big testing that we then put into one simple statement: this product is natureplus. So it’s really to make the complex communication as simple as possible.”
The natureplus eco label is a good indicator that a company has strong core values
Manufacturers must collaborate in the accreditation process by providing key information about performance, composition, etc. It also costs around 8000 euros to receive the label as well as an annual licence fee. The natureplus eco label is therefore a really good indicator of a sustainable product as in addition to the quality assurance, you also know the company has put in time and resources to achieve it.
There are three primary types of labels out there and it is important to understand them
Eco labels like natureplus, assess a product on the level of sustainability and should provide some tangible information about its impact and composition. The second type of labels are labels run by the manufacturers themselves. These labels will highlight some information about the product sustainability but they do the criteria development and assessment internally, which reduces transparency and lessens accountability. The third type of label refers to labels such as EPDs. As mentioned earlier, these are merely a declaration and it doesn’t say that this product really is environmental friendly or not. It is key to understand what each label means as each process has a different implication on the meaning of the label.
“A very harmful product actually could get an EPD. It’s good that they do because at least they are transparent with the information, but yeah, it’s not an eco friendly product necessarily.”
The Natureplus eco label is primarily based in Central Europe
Tilmann explains that natureplus is an international label and certified products are widely available, but the majority of the products are produced within Centural European countries. Sadly, there are no UK manufacturers with a natureplus eco label yet but there is hope for the future.
Exchanging ideas is crucial in the sustainable building sector
natureplus is a European network and in the face of the climate crisis, it is crucial that we are taking inspiration from countries with innovative ideas. Tilmann explains that we can turn to the architecture of Turkey to understand how to using shading to combat overheating or to the Netherlands where an innovative, pre-produced facade that can be assembled within days has proven to be popular. By tuning into the different solutions from European countries we can pool our collective knowledge to tackle many of the challenges that face us.
“Think global, act local”
The ultimate goal is to have enough natureplus products that you could build an entire house out of them
Tilmann explains that at present natureplus has certified approximately 600 different building products, from insulation to CLT timber.
There is a list on the website of all of these products. However, if you need to gather some more information about performance, some useful databases to use along side the natureplus product list are 2050s Materials, First Planit Materials and Powerbook.
Linda Farrow from Agile Homes explains how their prefabricated panelised system can deliver high quality and truly affordable homes that are good for the planet.
Interview with Linda Farrow
Linda Farrow and her partner Craig White set up Agile Homes in 2019 to address the need for better housing in the UK. They aim to deliver low-cost homes without sacrificing on quality, and each of their buildings is low carbon, energy efficient and has the ability to be disassembled easily (at the end of its life cycle).
Timber panels with straw in-fill are made off site
Linda explains that at the core of an Agile Home is their Modern Methods of Construction (MMC) panelised system. These panels are prefabricated in a factory and then assembled quickly on site, giving you a watertight structure within a day or two. The use of natural materials like timber and straw ensures that the homes have an extremely low embodied carbon and the panelised nature of the system mean it can be easily customised to meet the client’s needs. This makes it incredibly versatile and can be used for a variety of projects, from a block of flats to a one bedroom bungalow.
Their housing model aims to overcome common challenges
Linda explains that as part of their mission to make good quality and affordable housing accessible in the UK, they needed to identify the current barriers in the construction industry and come up with creative solutions to overcome them.
There is a cultural wariness of adopting renewable materials
England has a romance with brick and block construction that is proving tricky to shift. Even our children’s stories have perpetuated this message by telling us that a house made out of brick will be sturdy whereas a house built from straw and sticks will leave us vulnerable to attack.
This cultural mindset shift will take time to change but as more projects are completed it will keep demonstrating how well natural materials can work.
There is a lack of affordable land to develop
The price of land is currently a major barrier for affordable housing projects and often takes up a large proportion of the budget.
By collaborating with councils, housing associations and charities, Agile Homes works to unlock land at low or no cost for social value. This can quickly reduce the delivery cost by around a third.
It needs to be easier to finance and insure sustainable projects
It can still be a challenge to finance or insure ecological projects because they are deemed higher risk.
So Agile Homes has invested time in developing relationships with companies such as the Ecology Building Society and they are now an approved supplier.
They also gained BOPAS (Build Off-site Property Assurance Scheme) accreditation which is recognised by mortgage lenders as providing the necessary assurance that properties that use modern methods of construction (MMC) will be readily mortgageable for a minimum of 60 years.
Gaining planning consent is not always straightforward
Getting planning permission for a project can be quite involved and take time, which is why Agile Homes have developed a modular solution called TAM which complies with the Caravan Act. This generally means planning permission will not be required because they are moveable rather than permanent structures.
TAM (Transportable Accommodation Module) is a rapid response housing solution
TAM is a prefabricated, rapid-response housing solution.
The modules can be transported ‘flatpack’ to site and assembled quickly, leaving you with a watertight shell in a day or two and operational within a few weeks. Depending on the site and the needs of the client, TAM can also be umbilical to an existing building, using the same power, water and drainage systems without the need for planning permission.
“We’re not quite there yet, but one of our aims is to make it as easy for individuals and community led organisations to buy into our system as if they were going to a car showroom, and they can sign the finance agreement and drive away in their car. So in the same vein, they could sign a finance agreement and have their TAM delivered to their site”
Delivering a ‘turnkey’ solution helps to maintain quality
The larger the development the more likely it is that different companies and sub-contractors will be delivering different aspects. Inevitably this can lead to mistakes or inconsistencies. So at Agile Homes, where possible, they like to control the whole process.
“In essence it’s about control, and making sure that we can deliver the quality of product to the client. If you use a conventional procurement method where you’ve got the design and then you transfer over to a main contractor, the main contractor is incentivised to find all manner of ways to reduce their costs and increase their margin. And that’s not a criticism, that’s just the way the system is set up. We are a values led organisation and our board scrutinises everything that we do carefully. So I think it is about aligning everything that we do with our core value of respect for people and planet. It’s about control throughout the process to make sure that we can deliver to that time after time for our clients.”
Prefabrication can take place at a ‘pop-up’ factory
The panelised system has been designed so that it can be put together with high end power tools. In certain circumstances – such as at the request of a community led project – they can bring the manufacturing closer to site and create a pop-up factory in empty barns or industrial units. This has the added benefit of upskilling communities who are interested in sustainable building.
The Agile team
The best collaborators have respect for people and planet
“The ideal client would be someone whose values align with ours, so respect for people and planet, someone who has access to substantial amounts of patient capital, who is like us, genuinely interested in providing as many people as possible with homes that are affordable in perpetuity. Because having an affordable home, a safe civil space to be in is the foundation stone, in our view, for sustainable regenerative communities. And climate change is quite rapidly going to be a question of water and food crisis. So there are many, many immense challenges on the horizon for society. We want someone who, like us is very focused on helping society to put in place the foundation stone for us to then have the capacity to deal constructively with all the challenges that are yet to come.”
Inter-governmental policy is needed to be able to deliver widespread affordable housing
Linda explains that the biggest challenge for Agile Homes is access to patient capital and limitations caused by a lack of inter-governmental collaboration on housing policy.
“Governments have a duty in between terms and outside of party political allegiances to look after human beings and the planet. There are some policies that should be negotiated and agreed as being inter governmental.”
The natural materials contribute to a calm environment
Agile Homes has carried out work for local authorities, housing associations and charities, and quite a lot of their residents are vulnerable. This can range from physical disabilities, mental health issues to learning disabilities. So some key feedback they have received is that the natural materials and quality design have created a calm atmosphere which can be of great comfort to anyone but particularly to those with special needs or mental health challenges.
Agile Homes are committed to sustainability from their build system to their business model
Linda explains that Agile Homes aims to create a business model for affordable housing by looking at a wide range of resources which promote sustainability and social value:
The Agile Homes team is also in the process of finalising their Carbon and Social Value Tokens, which will allow people to offset their carbon emissions in local, sustainable, social developments.
“We’ve been thinking a lot about how to we evidence and generate revenue from the carbon storage that we’re achieving in our buildings and also in the social value that we’re creating. So we’ve been doing work behind the scenes to build calculators and we’re just about to go live with what we call carbon and social value tokens that can potentially be traded. What that means is that we have found clients who are interested in actually buying and paying for the stored carbon and the generated social value as part of their ESG governance systems and processes. So rather than offsetting their carbon footprint by paying for X 1000 trees, in a plantation 1000s of miles away, they’re choosing to buy the carbon that we can evidence is being stored for a minimum 60 year design life in our buildings and I think that’s very exciting. We have plans to use that methodology to generate revenue that can then further reduce the costs of some of our schemes for our most vulnerable clients. We’re really excited about that extension to the model and that rethinking of how do we generate value and revenue in a truly regenerative economy?”
Meredith Bowles from Mole Architects shares his experience working with timber as a construction material and explains the benefits and drawbacks of the different build approaches.
Interview with Meredith Bowles
Meredith Bowles, Founder and Director of Mole Architects, shares the pros and cons of different timber construction methods. Initially working on additions and conversions of Victorian building stock in London he found the masonry cavity wall approach unsatisfying, messy and difficult. So shifting towards timber construction was transformational. Meredith undertook his own self build project in 2002 and created a sustainable timber home that is still ahead of the government green guidance 20 years later. In this chat, Meredith sheds some light on timber build approaches including stick build, oak frame, CLT (Cross Laminated Timber), SIPs (Structural Insulated Panels), prefabrication and more.
Stackyard in Suffolk
Back to basics – What is timber?
Timber is wood that is prepared for use in building and carpentry, and if you visit a builders’ merchant in Britain this usually refers to white wood which is most likely to be Scandinavian, Lithuanian, or Russian softwood. In timber construction, this is most commonly assembled into stud walls which are sheathed and filled with insulation.
Although the UK has a medieval history of timber construction using large oak framing, the North American approach of using timber stud walls is still not as common as brick and block.
Over the last 20 years, engineered timber has been rising in popularity and involves binding or fixing fibres, strands, veneers, etc. into composite products to increase the strength and efficiency. Plywood is the simplest version of this, but CLT, LVL and glulam are also common.
With the wide range of timber products and construction methods available, timber is a fast growing sector of the construction industry in the UK and an obvious choice as we look to build more sustainably.
Alde Valley Barn ‘stick build’
Qualities of timber
Timber is a sustainable material with low embodied carbon impact
Timber is a renewable resource with low embodied carbon that can be engineered in a wide variety of ways to produce different results. Although timber in itself is sustainable, Meredith stresses that we must try to reduce our consumption of it and use it as efficiently as possible.
“Some advocates of timber make a claim that the growth of timber absorbs CO₂, and therefore, using more timber is a good thing. It’s a perverse kind of argument. If we are going to scale up timber construction throughout the world in order to try and minimise the use of more carbon intensive construction methods, then there’s going to be such an enormous demand on the available construction timbers. Surely it’s better to make it more widespread but to engineer the use of it, so that you are using less of it. I can’t square myself the argument that using more of anything is a good thing.”
Timber frames are better suited to accommodate insulation
Not only is timber a regenerative resource which during its lifetime will help with carbon capture and biodiversity, it also offers a logical way to better insulate our homes. Meredith explains how:
“There are a number aspects of sustainability, the primary one is cutting down our fossil fuel use and carbon emissions, which is what has been fuelling climate change. To do that, we need more insulation and if you’ve got a timber frame building, you’ve got a lot of space in it that you can fill up with insulation. It’s a really easy way of making a really well insulated building, because you’re building it out of stuff with a lot of space. The alternative masonry construction requires you to build two leaves with a really big gap in between to fit the right amount of insulation in, which becomes quite cumbersome and complicated.”
Timber can be utilised as a design feature or entirely hidden
Timber construction allows for more versatility and freedom with your design. Depending on how it is used, timber stud walls can be hidden, as it is sheathed on both sides, or incorporated into the design of the house through exposed beams or entire walls.
Timber is a warm material
Wood offers both an emotional and physical warmth that people respond to. The visual honey tones create a warm and soft interior but there is also a literal warmth in the sense that it has insulative properties. When you feel a masonry surface it absorbs the heat from your skin quickly and feels cold to the touch, whereas, timber doesn’t transfer the heat as well and feels warm.
Securing finance and insurance for a timber build can still be a challenge
Insurance companies and lenders still seem to view timber as non-traditional and therefore as a higher risk. Meredith highlights that these types of entrenched views are rarely as a result of statistical analysis and instead are built on a societal conception. As mentioned before on the podcast, the fairy tale of the little pigs has ingrained a sense of safety in brick-built housing and a sense of insecurity in one made of sticks, despite all of the evidence that suggests otherwise. As a result of this, there are more obstacles to overcome during timber construction which is stopping it being embraced by the mainstream.
“People say, ‘Well, I can’t get a mortgage for timber frame building’. Of course you can, but it’s not the norm, and therefore it’s slightly harder. Plus, I suppose if you go to any old builder down the road, and say, can you build a house, then they say ‘Oh, yes, we can build out a brick and block’ and they wouldn’t know where they’re going with timber. So it’s a whole industry which needs to change or is changing.”
Fire testing timber products
Fire risks are a common concern, but often exaggerated
The GLC (Greater London Council) has banned the use of timber in any external walls, because of the fallout from the Grenfell tragedy. Grenfell had no timber in the construction, and that was not the cause of the fire, but there’s been increased concern and cautiousness over anything that may be a problem in terms of fire as a consequence.
Timber needs to approached in a similar way to steel in order to resist fire damage
We all know that wood burns, but the reality of timber construction is that the timber frame is covered up, usually with plasterboard. Similar to our understanding of steel in construction, plasterboard is one of the best ways to stop fire reaching the material behind it and by encasing the structure, the heat is not going to reach the timber for some time. Incidentally, Meredith highlights that testing has shown timber to out-perform steel in the case that fire breaks through this barrier. As a result steel actually deforms, bends and can lead to structural failure much quicker than timber does.
Meredith recognises that much more research needs to be carried out in relation to fires, but does highlight that the government could be taking similar steps as Germany and Scandinavia by bringing timber into the same legislative framework that steel currently is in.
Knowing the charring factor of your timber can reduce the chance of structural damage during a fire
The charring factor in timber is another important consideration when it comes to the fire safety of timber framed houses. This refers to the amount of time it takes for the surface of the timber to char and lose its structural properties and how much of the surface is affected. As a result of this testing, timber used in construction has been oversized in order to compensate for the timber that would be lost during a fire so that it remains structurally safe.
The Black House
Meredith’s House
Meredith built his house in 2002 and got inspiration from projects in North America and Scandinavia, which had to deal with the harsher climate. The house consists of a prefabricated timber frame which was insulated using recycled newsprint/cellulose. Meredith’s home is in The Fens and it is common for building foundations to be piled with a concrete ring beam and a beam and block floor. However, to reduce the embodied carbon of his home, Meredith chose to use glulam timbers to create a ring beam above the ground, avoiding contact with water, keeping the structure well ventilated and dry. The finished house was even fitted with an air source heat pump, MVHR and solar canopies to help mitigate overheating.
The glulam timber ring beam
Construction of The Black House
When the Future Home legislation comes into force, the government guidance will have finally caught up with Meredith and his millennium home… just 20 odd years later.
Stick build is the most straightforward method for timber construction.
Stick build is when individual timber elements are cut and combined on site to form the structure. It is often sheathed by plywood or OSB to create a cavity for insulation.
‘Stick building’ at Riverview
Completed home – Riverview
Join The Hub to access the in-depth video case study of this timber build in Buckinghamshire
Moisture must be carefully managed in a timber structure
Materials like rockwool or glass fibre insulations are water resistant, which means any build-up of condensation in the wall cavity won’t be absorbed by the insulating material. This means that any moisture will run down the material and begin to pool at the bottom, slowly rotting the plate at the base and causing unseen damage that you won’t discover until it is too late. Meredith highlights that natural insulating materials such as cellulose, recycled newspaper, wood fibre or wool all have the ability to absorb moisture and then pass it out again. This means they take it in during the winter months and release it in the summer, helping to keep the timber structure itself dry and in good condition.
“Building physics has finally been properly understood and we put the layers with a greater resistance to moisture on the inside, and layers with a less resistance on the outside.”
Natural insulations are often not as effective as petrochemical insulations
When comparing the insulative properties of natural and petrochemical insulations, natural materials often don’t perform as well and therefore more is needed to reach the required insulation value. In projects where space and budgets are tight, this can be challenging.
“PIR foam is about twice as effective as any of the natural insulants, so you only need half the space and often when you’re trying to figure out how to fit everything in, that feels like it’s a much better solution. But of course, those insulants don’t absorb any moisture, so the way in which the building needs to be detailed suddenly has to change. We tend to use both forms of insulation in different circumstances because there are benefits sometimes of using a PIR that can get wet without losing its insulation capacity. The building physics of it are quite complicated, and it is necessary to get to grips with that to know how to use one insulation over another.”
Cross Laminated Timber (CLT) is generally used for larger projects
CLT is a form of engineered timber which is created by gluing together at least three layers of solid lumber. The layers are oriented perpendicular to the last, helping to increase the structural rigidity. The configuration of CLT differs from glulam beams in which the laminations are all orientated the same way.
Cavendish Avenue CLT construction
Completed home – Cavendish Avenue
CLT allows you to create a really strong structure whilst retaining the sustainability credentials of standard timber. However, Meredith says that for small scale, self-build projects, this building material is often not needed and would result in using more timber than necessary. There are cases where Meredith has used this material in private residences, but it was often to support the complex geometry of a design, so it is best to assess on a case by case basis. CLT is often best suited for large projects, such as public spaces, schools, etc and is a great alternative for steel beams.
Dune House – CLT
Structural Insulated Panels (SIPs) offer many structural benefits but tend to rely on petrochemical insulation
SIPs are quite broadly defined but Meredith describes them as “a sandwich construction of plywood or OSB on the outside faces, which are glued together with a polyurethane foam insulation, a bit like those ice cream with a wafer on each side.”
SIPs have amazing structural properties and it can be very easy to produce a highly insulated, airtight building using them. SIPs are incredibly lightweight so are easily transported, can be put together quickly, and will reduce your foundation costs.
However, Meredith has concerns about using SIPs in his projects as they require the use of fossil fuels to create and have a potential to release harmful gas from the insulation material and formaldehyde in the glues on either side of the sandwich.
Brettstapel solid timber construction avoids use of glues
Perhaps a less common timber build approach is Brettstapel. This is a simple construction method that allows you to create solid timber walls without the use of fixings or glues. Layers of timber are connected with wooden dowels instead of being glued together, which makes it strong. Meredith believes that, similarly to the use of CLTs in self build construction projects, Brettstapel is not the most efficient use of wood on the market, but the prospect of creating a structurally strong material without the use of fixings or glue is interesting.
Timber cassettes arrive on site
Prefabrication can improve quality control, airtightness and speed up on site construction
MMC (Modern Methods of Construction) refer to the prefabrication of buildings off site before on site assembly. This has the potential to greatly improve quality as the work is carried out in a controlled environment with the right tools on hand and properly trained staff which should lead to a more consistent output. Prefabrication also can include integrated services and windows, and much of the airtightness detailing.
As a result, prefabrication can offer a fast assembly on site, as the majority of work has been completed in a factory. This also minimises the chances of any delays due to adverse weather conditions.
“We’ve all heard the stories, my house was built in five days. Of course, we all know that’s not true, the prefabricated timber frame went up in five days, it’s probably been two months of doing the groundwork before, then it’s another nine months to finish the job. But nevertheless, it’s a very quick way of getting a watertight building and stick built but prefabricated cassettes is the next level up.”
Timber panel lifted into position
The benefits of MMC rely on good quality control practices being in place
Meredith highlights that the outcome of your build is heavily reliant on who is building it, and whilst prefabrication has the ability to increase quality control, it still relies on people to be implementing and performing the necessary checks.
“There’s no reason why a really low tech way of constructing something can’t be as effective and give you as good a quality as someone who’s using a much more automated system. I’ve visited various kinds of factories and our clients have received big consignments of prefabricated timber panels that have been simply incorrect because the quality control wasn’t there, irrespective of the fact that they have all of the machinery so they should be able to make it work. And conversely, we’ve worked with small contractors who are building it in a shed using a jig, two blokes and a tape measure, and it’s gone together perfectly. So, I don’t think there’s one way that definitely works and another way that doesn’t. I think different companies have different reputations and that’s how you should determine it. Talk to people who have used their products before, don’t just look at the fancy machinery and think that that’s got to be better.”
Development with TOWN
Solid oak frames might be beautiful but are not the best use of timber
Meredith is measured in his approach to construction, meaning that every project must be considered on an individual basis and no construction method is entirely off the table. However, he does raise some concerns with solid oak frames in modern construction.
Within the self-build world there is an attractiveness of a contemporary oak framed home, as it is what we see in the traditional vernacular of our buildings. However, with the developments in construction and a focus on sustainability and insulation, large oak framing for small projects is a very inefficient and unnecessary construction method. This is because once you have fitted the stud walls between the oak beams for your insulation, the stud walls could actually hold the structure on their own, making the beams a very large, beautiful but unnecessary feature. In larger buildings, the oak beams may be of more use to the structure.
“We talked earlier about the idea of minimising your use of materials and the idea of engineering something which is efficient is part of sustainable design, not overusing things. So there’s a slight illogic of using oak frame in a contemporary domestic building”
Meredith avoids using tropical hardwoods due to their link to deforestation in the rainforests
When buying timber look for FSC (Forest Stewardship Council) or PEFC (Forest Stewardship Council) accreditation which Meredith believes are governed well.
However, some time ago Mole Architects did stop using tropical hardwoods due to the links to deforestation and logging in rainforests.
“I think even though there are supposedly chains of custody and forms of logging that are deemed to be sustainable, it seems like the destruction of rainforests is of a different order or a different scale of environmental problems to the cutting down of forestry land that is grown for timber from softwood. So, you have to make a decision as to what you choose to do in terms of environmental provenance of the product.”
Every project is different, so try and choose the best method for your build
“My ambition as an architect is to explore ideas and every project is different, every client’s different, and I don’t come with a predetermined idea about what I want to do. So for me, the excitement is each time, it’s an exploration of a new project and what’s going to come out of it. I think that’s the same with the structure and the construction. There are so many different ways you can do things, the idea that one is better over another I don’t think it’s true. You have to figure out what is right for your project.”
Architect Kirsty Maguire explains why reusing an existing building is always preferable to demolishing and rebuilding. However, when buildings are in terrible condition or need radical alterations to make them habitable we should be looking to reuse, recycle and reclaim as many materials as possible. Kirsty shows us that with intentional and sustainable design, you can create a new structure with a wealth of history.
Interview with Kirsty Maguire
Kirsty Maguire is an architect and Passivhaus designer who specialises in reclamation practices and sustainable building. Along with her team, Kirsty has been involved a wide range of projects that focus on finding ways to recycle the wealth of resources in existing buildings and reclamation centres, instead of buying new. In this chat, Kirsty explains the steps that are taken throughout a reclamation centred project and describes how preloved items can bring beauty and creativity to your home.
Reusing and reclaiming materials is an essential part of sustainability and the future of construction
A lot of the narratives around Passivhaus certification and sustainable construction have a focus on new builds. Whilst these projects are great, we can’t solely focus on sustainable new builds for the future of housing. Kirsty highlights that we currently have a wealth resources in already existing structures. We don’t have the ability to start from scratch on everything, so reclaiming, renovating, and reusing will be fundamental for a strong circular economy and in creating a sustainable future of housing.
“We’ve done everything from little cottage upgrades to working with the UNDP in Armenia doing big, tower block retrofits. And that’s really, you know, that’s what’s going to change the world in a short time.”
What is the circular economy?
“Circular economy is looking at materials not only in the use that they are now but also beyond that use and into their next life.”
The Seed
The Seed is a new building constructed just outside of Dundee on a woodland plot. It is a home for two families and acts as a small-scale cohousing project, with shared access to living areas. When the project was originally brought to Kirsty and her team, it was intended to be an EnerPHit project on an existing structure, but after reviewing the building health, the team realised that the structure was in a very poor condition with a lot of damp.
“We drew the things that we’re going to have to be taken out in red and the drawings were almost entirely red! There was very little left.”
As a result, the goal shifted from reuse to recycle and the team formulated a plan to demolish the existing structure and reuse as much of the material as possible in the new building. Bricks were used in a range of different ways, creating gabions that formed the foundation of the structure, as aggregate on the site and also in the garden to provide structure for the biodiversity growing that the client is developing.
The client was passionate about sustainability and biodiversity being at the heart of the project, which can be seen in the construction methods, choices of materials and the overall design of the house.
Reusing materials might mean changing their use
Not all reclaimed materials will be able to be used in the exact same way as they were before, so there is an aspect of creativity needed for designers to work out how to use them in new projects.
You don’t need to demolish an existing structure to be able to reclaim materials
There are some great resources out there for sourcing reclaimed materials, whether that be from architectural salvage yards, stone yards, and even online sites such as eBay, Gumtree and Freecycle. A great example, local to Kirsty, is Dundee Scrap Antics, which is a creative recycling and social justice enterprise, that aims to give preloved items another life.
“They might have something that’s been sitting in the back there for years and years or even decades, which is exactly what you need for your project. So there are a lot of places you can go.”
Finishes are the easiest way to reuse in a Passivhaus
Structural components can be a bit harder because there won’t be any manufactures data to prove the efficiency of the product, in particular insulation. But this matters most in Passivhaus structures as you need this data to get the certification. Therefore, using reclaimed materials for your internal finishes can be a great way to improve the sustainability and character of your home.
Our current building industry doesn’t consider the richness of reclaiming materials
The current system is designed to make you go straight to the merchant and buy any materials new, it is considered efficient in both time and cost. But it doesn’t take into consideration the benefits of using reclaimed materials on the environment and the unique quality of the finished product.
“It doesn’t take into account the rich wealth of recycled materials that exists out there.”
Demolition companies are incentivised to separate waste and avoid putting everything into landfill
With the presence of substances like asbestos, demolition has moved past the time of a wrecking ball and a skip. Now, it is a much more measured process, but there are still important considerations to be made and does depend on where the reclaimed material is used afterwards. Often, demolition companies have the materials taken away to be used in other projects, but Kirsty highlights that whilst this is much better than them ending up in landfill, the most sustainable use is in reclaiming materials and reusing them on the same site. In the case of The Seed, the asbestos was professionally removed, and the majority of the timber and plaster was taken to be used on other sites, but pretty much all the rest was reused on site, whether that was in the building itself, landscaping or in garden structures.
Surroundings can be a big influence on the design
In the design of The Seed, the woodland area in which the site is situated, influenced a large amount of the design as well as the environmental performance. Internal layout can be designed to maximise the connection to the outdoor space and the use of two different colour clay plasters inside differentiates between the two families’ zones in a cohousing living space. As a result, you create a warm atmosphere both thermally and emotionally, that sits within the land not on it.
“As the client described it, almost womb like. Very enveloping and warm and cosy. Not only from a thermal performance point of view, but from a sort of emotional point of view.”
You must not only consider how the building will be constructed, but also it’s deconstruction in many years to come
The construction of The Seed focused on installing root protection and avoiding the use of concrete and cement when laying the groundwork. They decided to use steel screw piles for the foundation as they could position them in relation to the tree roots and can be removed with little impact at a later date. Kirsty also pointed out that even if the steel piles can’t be reused in a future project, they can be recycled.
“This comes back down to the thinking about the whole building life. So you in the same way that we were looking at the previous building that was on the site, that was at it’s end of life, and identifying the type of materials that we can reuse within that, despite the fact that when it was built that wasn’t what was being considered. What we’re looking at with a new building is how that building could be taken apart at the end of its life… steel screw piles can be taken out with relatively small impact on the ground, and considering other materials as we go through as to what can be reused and recycled when it does come to that point”
… and it’s embodied carbon impact
Kirsty was yet to receive the data for the embodied carbon of steel screw piles, but did highlight that it is often the renewable energy devices that hold the highest embodied carbon of a project. You can influence this, depending on where you source you Solar PV, for example, can have a big impact on the level of embodied carbon. It is therefore much easier to control the embodied carbon of your above ground materials and it is often about looking at how to balance it all.
Remember to consider your waste management
Kirsty explains that in the construction of The Seed, they highlighted that root protection was an area of potential waste as it requires a large quantity of gravel. To get around this, they were able to use reclaimed materials from the demolition and any left-over material was used in another of their building sites.
Root protection has many benefits
Root protection is often a planning requirement for sites that have trees surrounding the foundation. The Seed was being constructed on a woodland site with many mature trees and root protection was required. The team found that not only did this process protect the trees, but it also protected the soil during construction and helped to avoid the perils of a muddy, winter, construction site!
“the contractor commented that they really loved having the reputation down because it meant that the site was very clean… you’re not wading around in the wintertime, with mud up to your ankles, tracking it through the whole building site.”
Aim to continue the ethos through every stage of your build
It’s not only the shell that must be considered when creating a sustainable home. When you carry a mindset through every step of the process, right down to the internal finishes and furnishings, you achieve a cohesive design with much more intention. Kirsty talks about how Caroline (the client for The Seed) achieved the majority of her internal finishes with furniture she already owned, or second hand finds, rather than buying new and contributing to landfill waste. Each feature tells a story, in particular, the wooden platform made from materials reclaimed from the sailing club in Broughty Ferry that her site manager was involved in constructing all those years ago. This continuation of her overall ethos has created not only a beautiful design but a sense of history within a new structure.
“It’s really interesting. So unexpectedly, these little stories start to come up and get created about the building too”
Remember to consider the biodiversity and ecology of your site
Kirsty also highlights that biodiversity and ecology are at the centre of their practice when renovating, demolishing, and reconstructing buildings. The presence of bats is a common occurrence in reclamation projects as these structures have been standing for a long time and it’s not only the previous owners that will have called them home. It is therefore important that the proper surveys are done, and any findings must be checked by a local ecologist.
“What’s existing there already? It’s not just the humans… who call the houses their home.”
Collaboration and a good team is key
Having a team that all share the same goal for a project is vital and if overlooked you may end up with a different end product than what you had envisioned. Storage in key when reclaiming materials as they will often be sat around for a while before they can be reused and in that time, they need to be stored within the right conditions. This requires an additional level of planning and coordination, so a good team that all understand the ethos of the build is crucial. Without this, things may become very difficult.
“It might be that the architect and the client find some amazing things together in terms of materials to reuse. But if you’ve working with the wrong contractor, then they’re not going to be picking that up or vice versa… But when you get a great contractor to work with, or anybody else from the design team or the or the build team, then everyone putting their heads together to find solutions really can make the reused materials sing.”
Don’t be overwhelmed by the prospect of reusing and recycling in your build
Once you get into the process it can be really fun and exciting! Reclaiming and sourcing second hand materials can be a creative exercise in problem solving. You will likely end up with a range of unique and high-quality features in your home that will each tell their own story.
The industry has come a long way in the past 10 years
10 years ago, it would have been very difficult to find data on embodied carbon and embodied energy but today there is rich data base to help guide you. PHHP is a relatively quick modelling tool which also has a feature to check the embodied carbon and embodied energy of materials, allowing you to begin the process at a relatively low cost.
“if you’re using PHPP… then you can choose whether you think that extra 50 millimetres of insulation is worth the cost or not and… that puts the control for specification and budget firmly in the design team and clients pocket, which is fantastic.”
Copyright – Grant Anderson / www.grantanderson.me / @grantandersondotme
Your project shouldn’t feel like a juggling act of different goals
Building projects should aim to have your goals working together cohesively rather than battling one another. This brings us back to our topic from last week; embodied carbon vs energy efficiency. Kirsty explains that we shouldn’t view them as competing goals, but instead as different factors that need to work together. You don’t need to forgo one to have the other, but you may need to spend a little longer working out how you can get them to work together harmoniously.
“thinking about the impact of the construction, in the same way that we’ve been able to look at the performance is a really powerful tool… For a long time, we were focusing on performance, and the decisions that you might make instinctively are often right, but they’re not always. And it’s exactly the same with embodied carbon and embodied energy.”
Antoine Costantini explains how Kithurst Homes has embraced modern cutting technology to increase efficiency and minimise waste.
Interview with Antoine Costantini
With a background in physics and trouble-shooting in the construction industry, Antoine has always loved working with timber. He explains that engineered timber is a great way of using the material responsibly and with less waste.
There are 4 main types of engineered timber that Kithurst Homes use
These are:
Laminated Veneer Lumber (LVL) – “Like a plywood on steroids”
KVH – Finger-jointed soft wood
Cross Laminated Timber (CLT) – A cross lamination of timber in opposing directions
Glulam – Soft wood glued together
Automating the process is faster and produces less waste
Previously they would use a large chop saw to cut frames by hand, which meant manually changing the direction each time a different angle was needed. This would get repetitive and there was the risk of human error so they looked for a way of automating the process.
The Hundegger machine they now use is a five axis saw which enables them to make cuts at any angle and inclination. It has also reduced the time it takes to cut, mark and pack a 200 square metre frame from two and a half weeks, down to three hours! On top of this there’s now only 3% wastage.
The Hundegger software reads and cuts from various file types
One of Kithurst’s customers is Passivhaus Homes with their PH15 method of construction. They send over their completed BVX file of the timber frame design, which gives the machine all the information it needs.
Get access to our in-depth video case study of Buckinghamshire Passivhaus, a PH15 build, in The Hub
Kithurst Homes also work from DWGs or can convert a hand drawing into a 3D image that the saw will then read.
The machine software creates a picking list
This will tell the operator the amount of I-joists, glulams and LVL that will be needed. These are then manually placed in order of size and fed into the machine.
The machine is clever enough to recognise the material that is being fed in, and will alert the user if the geometry of the material doesn’t match with what it has been asked to cut.
Using I-joists is an efficient way of building
They use less timber than a traditional stick frame approach, and also reduce cold bridges because of their size and geometry. They arrive at the factory in 13 metre lengths, with Antoine estimating that an average frame would use around one kilometre of I-joists.
The combination of the web of the I-joist with incredible shear strength and the lamination of the flange gives the I joist its strength and load bearing capacity. The regularity of the timber makes it predictable, and that is a good thing in engineering. They know how it will react on strength, density, bending, modulus, and shear.
If it’s not compostable or recyclable they won’t use it
Once the timber has been cut, numbered and marked, it is packed together by wall. Steel bands are used to secure them, as these can then be recycled whereas the plastic alternatives can’t. They are then stacked and transported to site by curtain sided trucks. Once on-site there is no need for a skip, as everything fits and there is no wastage. This complies with the company ethos of trying to preserve the environment as much as possible, and not using PU or polystyrene foams for example.
It just takes common sense and DIY skills to put it together!
Kithurst Homes will always provide training, whether that be on site or at their factory, in how to construct the frame. With everything being marked, it’s a case of needing to be bound together, and Kithurst Homes provide all the fixings, the screws, the staples, the membranes, the plywood.
Antoine says that anyone with good DIY skills can put together their flat pack systems. Some of the parts can be heavy so may need extra pairs of hands, but generally because the I-joists use so much less timber they can be quite manageable.
Their full wall systems however require craning in and a team of carpenters to put together.
All their timber is PEFC certified
The timber comes from two or three manufacturers, with Steico in Germany being where they get their wood fibre insulation, LVL and I joists. It is fully certified to European regulations and Kithurst know their suppliers are using the timber properly, with everything on the tree being used and documented.
Mick Woolley explains how the use of timber was a key element of his award-winning Passivhaus bungalow.
Interview with Mick Woolley
For the last two years, Mick Woolley has been living in his Larch Corner Passivhaus which was the Small Projects winner in the 2021 UK Passivhaus Awards.
His self build journey began following the loss of his wife. He had long held an interest in self building and took the attitude “what could possibly go wrong!”
Initially beginning his search in the south east of England to be closer to his two sons in Surrey, Mick found a lovely plot, surrounded by a vineyard, and just 30 miles away from them. But despite the proximity, it had taken an hour and a half to get there and was £450,000 before he’d even knocked the existing bungalow down. It was at that point he decided to abandon his search in the south east and opened up to looking at sites as far afield as North Wales and Cornwall.
They made changes to the planning designs
Mick saw a plot on RightMove, that seemed to be in a pleasant village location at the northern tip of the Cotswolds. Close to a National Trust garden and Stratford upon Avon, he felt he would be able to find enough to do in the area and was surprised when he managed to purchase it for around the guide price at auction. It came with planning permission for a single storey Passivhaus with a design that he admits probably didn’t appeal to everyone, and is why he thinks there wasn’t more competition in the bidding.
Although not put off by the design, he was sceptical of its Passivhaus credentials and enlisted Mark Siddall of LEAP to re-work the plans. He did however want to keep it a bungalow to make it accessible for a family member who uses a wheelchair, but also because it future-proofed it for him too.
The original design had a lot of corners so they removed some of these and also had to raise the roof to ensure there was adequate head height for insulation. They swapped the entrance hall and study around to ensure a better flow into the house, and took out the many corner windows from the plans. Mark instead designed an arrangement of windows that came in 2 sizes: smaller ones for the bathrooms and bedrooms, and larger windows with seating elsewhere.
Timber was an important element of the design
Mick wanted to build using Cross-Laminated Timber (CLT), as much for the visual impact it provided inside as for its structural qualities. The bungalow uses 17 sections of spruce timber, which have 6 layers, are edge-glued, and don’t require an airtight membrane around the outside.
The roof came with a cassette of insulation in it so the structure went up in two days, and had an airtight wrap over the top by the end of the third day. The walls are made of an I-frame structure with blown-in wood fibre, giving a thickness of around 600mm and a U-value of 0.1.
The exterior of the bungalow has larch cladding.
The foundations were pre-cut to size
The building has a Jackon XPS foundation which was pre-cut to the required size and slotted together, with an XPS upstand that locked into the perimeter. This created its own formwork for the concrete pour.
The flat roof has a camber of around 5 degrees for shedding water. On top of the insulation is a cold roof section of ply and bitumen that provides the finishing structure on which to put the green roof. Mick says he checks up there from time to time just to check that seedlings for trees and other unwanted plants haven’t blown in and taken root!
He was keen to be hands-on
With Mick being on-site throughout the build process he was keen to get involved in any way he could, so one task that he took on was the airtightness taping. His top tip for getting it into the corners is to ideally bend the tape in two in order to push it in and get good contact right the way through the junction.
The straight lines of the 17 sections of CLT only took an hour to do, but all the other joints around the doors and windows took a lot longer!
Mick employed Alan Clarke as his M&E engineer and he carefully designed the ventilation system so it could go through cupboards and be kept out of the way, but still accessible if needed. The full design with all of the MVHR kit was supplied as a single delivery, and Mick took on the installation of the pipework himself. Not having any experience of doing something like that, he did find it took him a very long time to put together!
There is around 140 square metres of floating floor, which was designed to be laid to flow through without any junction strips at doors. His builder Andy took time to work out the geometry to ensure that boards were centred and wouldn’t end up with slivers at the edges, which Mick was then able to lay.
Always make space for storage!
Although Mick was adamant that he wanted to use CLT, he now realises that he could have been more efficient with materials and created the timber finish that he was looking for by using large sections of three-ply timber.
If he were to do the build again, he would probably opt for a two-storey building, though still keeping a downstairs bedroom. He says that the UK housing stock is generally fairly deficient in terms of providing for the elderly and those with mobility problems, so designing at least one bedroom downstairs is really important.
Mick says that going for a two-storey design would improve the form factor and use a lot less insulation. It is also more efficient in having less foundations and roof.
Lack of storage space is often a real problem in typical new build homes, but Mick is delighted at the amount of space they designed into his home, including a large storage wall. He also has a double garaged sized shed, although this is currently housing lots of off-cuts of CLT and three-ply materials that are waiting to find a home!
He emphasises why it’s always a good idea to build into the loft as that’s also potential space that can be used for storage.
Neil Sutherland explains how using a design, manufacture and delivery company can give you a better quality of construction.
Interview with Neil Sutherland
Neil didn’t take a conventional route into architecture. After leaving school at 16 he undertook a technical apprenticeship with an engineering company for a few years. It was only after finishing his apprenticeship and going travelling around Europe that the wonders of Florence turned his head to architecture. He returned to Scotland, completed his degree and promptly set up his own practice, MAKAR, an architect-led, ecological design and build company.
Makar House, Kinloss, Morayshire, Scotland.
A unique entity focused on the delivery of great places
Neil summarises MAKAR as not being an architectural practice, builder or manufacturer, but a combination of the three.
His first ten years in business were spent working out how best to develop and design buildings, and was disappointed by the options available to him on the delivery side of things.
When he moved to a live on a farm with his family around 16 years ago, he had land available where he was able to develop and grow his business to include the manufacturing. He now has a couple of large workshops and employs close to 50 people.
Their unique offering means they are currently working at capacity producing homes mostly in the Scottish Highlands, but are also looking to mainstream what they do and make it more widely available.
Certainties can be provided to clients
Neil is able to offer certainties to clients, around design, programme, workmanship and cost. With the alternative being to work with a number of consultants and a builder, he says it can be difficult to find a company who are motivated by ecological progressive areas of working who are able to take on an architect’s idea and make it work.
“As I’ve learnt over the years, the intention is the first stage but one has to figure out how to get things delivered. The execution of things is perhaps far more challenging than coming up with bright ideas.”
There are three aspects to a successful project outcome
The first is having a thorough understanding of the client’s brief. This involves taking time to sit down with them and really understand their needs.
The second aspect is the site analysis. Every site will have constraints and opportunities, but there’s always context; things to respond to, things you want to exemplify or even perhaps reduce.
The third element is a flexible delivery approach.
Neil believes as long as none of these three aspects are compromised, as he suggests happens in the standard approach to the design and delivery of housing, the customer will end up with a wonderful outcome.
Scotland has an abundance of quality timber
Scotland’s forestry cover has an unusual species mix, dominated by pine, fir, larch and spruce.
Neil’s company is looking to develop progressive ways of utilising that timber, from a structural perspective right through to insulation. They use the common characteristics of those species for different applications and avoid using chemical treatments wherever possible.
Spruce and Scots pine for example can be used for the carcassing of a panel type construction, Douglas Fir for large section exposed beams and posts, and larch is used extensively on the external applications of buildings, such as cladding and decking.
“There’s enough there to do everything we want to do, to do it without chemical treatments, and to work in anticipation of the circular economy, in anticipation of the idea that timber buildings are uniquely adaptable in the sense that they are repairable and you can change them. You can take them apart and put them back together again.”
They work closely with sawmills
In other parts of the world, and particularly in Europe there are many small to medium sized mills, which relate to their local resource and how it’s used. In Scotland, many of the small to medium sized mills haven’t survived so MAKAR tend to use a few large sawmills along with a small number of smaller ones.
Rather than the usual design approach of designing something and then looking for what you’re going to use to build it, in normal situations they would look at the resource available and respond to that, buying the timber directly from the sawmill.
They use a lean process
Lean process improvement is largely used in manufacturing to improve efficiency and reduce waste.
Neil’s interpretation is that it’s about people; what motivates them to do things carefully, and with a lot of attention to detail, getting things right the first time and really enjoying what they’re doing.
“It’s when you go about making things, when you connect the theory and practice of things together, you get a third thing that comes out which is a kind of tangible, pragmatic capability which is not held up as important as it is, in actual fact.”
And Neil believes it is the people who are making things who are the best people to ask about how to improve the process.
An ecological approach to engaging with the world
MAKAR use the term ‘meaningful work’ to explain their working methods. It’s about their work being respectful to everyone involved, and respectful to things beyond themselves.
“Every time we build a house, we know that it’s going to impact on people’s lives in a very profound manner. MAKAR exists because we believe that great buildings and places change people’s lives.”
The aim is for quality, not speed
The main constraint that MAKAR have with building the houses is the transportation. Their standard panel size is around three metres wide so that it can be transported by road relatively easily.
Such off-site construction methods may be more expensive than other alternatives, but they will be better and more consistently made and speed and cost reductions will come about over time.
The pieces of the house are made in sequence: first the floor, wall and roof panels, then the post and beam elements and finally the modular elements which are the parts of the house that have the plumbing, ventilation and electrics in them.
They try and do as much of the servicing within the modules at their workshop as possible as they believe this to have the best outcomes.
“But the future is about having less and less equipment, more and more fabric first, more and more simplicity around buildings really. But use the word optimisations. So, what equipment you do have you have to make sure it is working well and it’s optimised.“
Interior designer Emily Bizley explains how she and her husband, an architect, co-designed their RIBA shortlisted self-build home.
Interview with Emily Bizley
Emily wanted to be an interior designer since she was very small, but ended up studying French and Psychology at university before deciding to go to Chelsea Art College to pursue her childhood dream. After gaining more qualifications, Emily worked for architects to get some experience. From there she went to work for an interior designer in London, and now has her own practice based in Somerset.
The interior shouldn’t be an afterthought
If design decisions aren’t guided by “a bigger idea about what the building is supposed to be”, there’s a risk that the interior and exterior won’t be coherent. Emily explains they wanted to build a timber house that was sympathetic to and connected with the surrounding countryside and nearby agricultural buildings.
She says she’s visited a lot of timber clad houses that look fabulous on the outside but whose interiors are “a crashing disappointment because it’s all white plasterboard with twinkly down lighters and absolutely no atmosphere.” She finds it surprising these houses aren’t made of wood both inside and out, like those she and her husband visited in Switzerland.
Ask yourself how you want each room to feel
Emily and her husband both did a lot of sketching for their self-build. They focused much more on how they wanted a room to feel, rather than how it would look. Sketches of room scenes helped them imagine their lives in the new house and captured the desired atmosphere.
Design the interior and exterior in partnership with one another
Focusing on how they wanted the kitchen to feel took them through a series of questions; the answers defined the design inside and out. For example, thinking about what they wanted to look at while eating breakfast, and where the sun would be coming in, suggested the size and position of the windows. But then they had to consider how this would affect the elevation outside, and the design needed tweaking to get to the point where it worked inside and out.
Emily says they decided to have their sitting room separate to (but adjoining) the open plan kitchen dining area. They designed this room to be a half level up with the ceiling following the roofline down, making it a cosy snug. She explains the materials they used are the same, it’s just that the space has been slightly manipulated to create a different atmosphere.
Think about how natural light will reach all the spaces
Emily’s house has light from all sides. She says it is really important to ensure that the darkest parts of the house still get natural light. They incorporated skylights into the design for their self-build, to avoid any “dark dingy corners”.
Create interesting relationships between spaces, inside and out
The sloping site presented challenges. Emily explains, “A developer house would just be plonked on stilts at the front to make the site flat, but then you lose the relationship to the garden”, adding, “We didn’t want that feeling of being on the upper floor and feeling really disconnected from the garden.” Instead, they dug down to enable the house to sit back in the hillside and decided to go for an upside down layout, taking care to create access to the garden from different places.
Their self-build uses internal glazing to create interesting relationships within the house – the rooms aren’t “a series of boxes with doors”. Emily says that internal glazing was something she and her husband had always liked about French houses and had been on their list of things they’d wanted to incorporate into their designs.
Be generous with some spaces to create the right atmosphere
Sometimes it’s worth sacrificing a bit of space to be generous elsewhere. In the case of Emily’s self-build, the design for the lower floor incorporated a wider hallway. She doesn’t see this as wasted space as it avoids the feeling of going downstairs into a rabbit warren of bedrooms.
Restrict the palette to avoid a “mishmash of everything”
There are a lot of options when it comes to interior finishes. Emily says they were quite disciplined in having just a few ideas for their interior and carrying those through with some rigour. She describes the house as having “two quite distinct overall sorts of atmosphere”. The rooms are either lined with oak or painted plywood; no walls are just plastered. And some of the ceilings are crafted from rough-sawn softwood and painted.
A joiner made their bespoke kitchen and he sourced the wood from the same supplier used for oak lining the walls. Emily comments, “The kitchen is intended to look like the walls, and blend in.”
Think about furniture early on as it impacts the design
Although Emily believes it’s good to let ideas develop and to be able to respond in an organic way, it’s also important to have an overall idea when it comes to furniture. She uses their veranda as an example, explaining that it is pretty much square in plan, but as the house is not a square box the corner of the deck intentionally gets wider to accommodate the table and chairs.
It also helps to know what you’re planning to do furniture-wise to produce electrical plans. For example, do you want to sit in a particular well-lit corner and read? The position of an extractor fan in the kitchen is another important consideration – what type of cooking do you tend to do, and does that require extraction directly above the hob?
Factor in storage during the design stage
Emily comments, “If we did decide to put everything away, there would be a space for everything.” The big store at the back houses the plant, store and utility rooms. They also incorporated really big wardrobes into the kids’ bedrooms and Emily and her husband have a lot of storage space in their dressing room.
Other tips for self-builders
Collate images of anything you really like into a folder
Have some clear ideas and follow them through – don’t get distracted
Think about how materials and texture can achieve the atmosphere you want
