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.
Jeffrey Hart from the Earthen Floor Company gives us the lowdown on natural earth floors, explaining what the components are, how they are mixed and the process of installing them. He also outlines the benefits and limitations, and highlights what makes them a great choice for an eco home.
Interview with Jeffrey Hart
Jeffrey Hart got into natural building in Oregon, USA, where he was an apprentice of earthen floors expert Sukita Reay Crimmel. He spent five years constructing various buildings and installing earth floors in each of them, before returning to the UK. Although he started out as a ‘generalist’ natural builder, as demand grew, he found himself focusing exclusively on earth floors through the Earthen Floor Company. He credits Sukita’s influence for both the modern earth floor technique and the resurgence of this historic building method.
Earth floors have been used for centuries
Historically many buildings would have had an earth floor just because it was the ground beneath the building. At some point, people realised that cow dung reacted with the earth to make it a harder, more waterproof surface. It was also noted that when blood fell onto the floor of farm slaughter houses it made the earth rock solid, so over the years different methods have been used to make the floors harder and more durable. Sukita developed a way to use linseed oil to seal and harden the clay, making it a lot more palatable for the modern world and the way we live now.
All earth floors have a binder, an aggregate and fibre
Earth floors – also known as earthen, cob or adobe floors – all have a binder, an aggregate and fibre. In Jeffrey’s case the binder is clay, the aggregate is sand and the fibre is either straw or hemp.
The process of making an earth floor is similar to that of a concrete or limecrete floor, but clay’s ability to hold together is lower than lime or cement, which is why linseed oil is added.
“The linseed oil turns the floor from something that’s relatively soft and quite easily damageable, to this hard-wearing, leathery rock.”
Earth floors can be structural or just the top coat finish
An earth floor can serve as a thin finish over an existing concrete, limecrete or even timber floor, or it can be built up as a full‑thickness slab. The minimal approach involves a 20 mm top coat, while the full build‑up typically incorporates foam‑glass insulation, optional under‑floor heating, a rammed‑earth base and a top coat.
Jeffrey’s preferred full build-up
Moisture must be managed to avoid problems
Moisture is a critical concern for earth floors and Jeffrey will use membranes if damp conditions exist and foam‑glass insulation as it acts as a capillary break, preventing upward moisture migration. It is also important that the floor dries out sufficiently before the linseed oil is applied.
Linseed oil is used to cure and harden the surface
Linseed oil is the “magic” component that transforms a relatively soft, clay‑based mix into a hard‑wearing surface. Once the clay dries, the oil polymerises, linking long‑chain molecules to create a leathery, rock‑like finish. Without sufficient oil penetration, the floor remains soft and prone to damage. The oil also imparts the characteristic warm brown hue that many owners associate with earth floors.
The embodied carbon of earth floors is extremely low
Switching from a conventional concrete floor to an earth floor can reduce embodied carbon by roughly 83 % (according to calculations using the BEAM Estimator). The reduction stems from using locally sourced clay and sand, eliminating the need for high‑energy cement, and the floor’s ability to be broken down and returned to the earth at the end of its life cycle.
“It’s about an 83 % reduction if you were to swap like for like.”
It is possible to use clay from your building plot
If you’re digging the foundations of your house and the spoil is clay, one option is to reuse it in your floor. Jeffrey believes this is the ultimate local and sustainable floor, but there are a few considerations. Most important is to test the soil to confirm that it is clay rather than silt, which lacks the necessary binding properties. Tests assess shrinkage rates, strength, and colour consistency. Variability between layers can lead to inconsistent performance, so careful excavation and sampling are essential. Unfortunately, using local clay isn’t necessarily cheaper because of the required testing and processing, so the Earthen Floor Company offers pre‑bagged mixes with clay sourced from reliable brickworks and pottery suppliers.
A lot of the cost is down to the labour
The current rate for a finished earth floor from the Earthen Floor Company is £160 per square metre for the top‑coat package, which includes materials, labour, buffing, and waxing. Prices vary with location because of the extra travel but if money is tight, self-builders can do the final oiling and waxing themselves.
You can’t walk on the floor for a month while it’s drying
Although an installer might be able to cover 10 m² per day the whole floor must be completed in a single day. This means multiple installers coming to site, the number depending on the size of the floor. After the mix is laid, the floor must dry out before the linseed oil is applied. The drying time depends on ambient temperature, humidity, and air flow; heaters and fans can help accelerate the process, but Jeffrey recommends not trying to speed things up too much as there can be unintended consequences. Once dry, the floor is oiled and then left for a further 14 days to harden.
“From install to you being able to use the floor it’s three weeks if everything goes well.”
Underfloor heating works well with an earth floor
Earth floors store heat efficiently, making them ideal for radiant heating systems. The heating pipes are usually positioned between the insulation layer and the rammed‑earth base, though some projects place them higher in the slab for a faster response in properties that may not be used all the time (such as holiday lets). The thermal mass of the earth floor prolongs warmth after the system cycles off, reducing temperature swings and improving comfort.
Repairing minor damage to the floor is quite easy
A well‑installed earth floor would be expected to last at least 30 years, becoming more beautiful as it ages. If you damage the floor, making a dent or chip, it’s actually not too difficult to remedy. By crushing leftover “biscuits” (small pieces of the original mix), mixing them with oil, you can fill the crack. While repairs are relatively seamless, they may be visible in certain light conditions. To protect your floor it’s a good idea to oil and wax it as part of the maintenance cycle; the oil’s polymerisation continues slowly over the years, gradually increasing hardness.
“We make little biscuits from the mix leftovers; they’re used to patch dents.”
It is possible to choose the colour of the floor
The natural colour of an earth floor ranges from earthy browns to greys, dictated by the clay’s mineral content and the colour of the linseed oil. To achieve brighter hues, pigments can be blended into the mix, producing uniform colour throughout the slab. Alternatively, a coloured hard wax applied as a surface finish can modify the appearance without altering the underlying material, though this layer may need to be reapplied every couple of years. Most self-builders prefer the authentic, warm tones, but designers increasingly want something bespoke.
“People are becoming more aware of this material now; it’s no longer just a niche.”
There are lots of reasons to love earth floors!
As natural materials are much more accepted these days, earth floors are seeing a revival. Jeffrey has also been doing his bit to train the next generation of installers. He is trying to make earth floors as accessible as possible as he really believes in them. They look beautiful, they feel incredible under your feet, they soften sounds and are good in terms of carbon emissions.
“And at the end of the product’s lifespan, you can break it all up, chuck it in your garden, and it will break down to be just earth again.”
Stephanie Kyle from Floyd Slaski Architects explains how we can design for disability, gender, religion, and anything that’s considered a protected characteristic under the Equality Act. She also highlights the biggest challenge of inclusive design which is people’s differing needs, and suggests how we best go about designing spaces.
Interview with Stephanie Kyle
Stephanie Kyle is a Senior Architect and Inclusive Design Consultant at Floyd Slaski Architects, who specialises in design for neurodiversity.
Stephanie was diagnosed with Auditory Processing Disorder (APD) when she was a child, but it wasn’t until her 20s that she found out she was autistic. APD is a neurodivergent condition and because this was identified early she didn’t have to grow up masking her behaviour to fit in, and got the support she needed at college and university.
Her inspiration for entering the world of architecture came early on during a workshop at her school. An architect wanted to hear their ideas about an aquarium that was being proposed in the town. When it was built, she went on a school trip to see it, thought it was atrocious and that she could do a better job herself!
Throughout her education and architecture training she was drawn to inclusive design, which includes designing for disability, gender and religion, everything that’s considered a protected characteristic under the Equality Act. She now specialises in neurodiverse, inclusive design and nonvisible disabilities; focusing on how we can design better for dementia, autism, ADHD and all the nonvisible conditions, like epilepsy or chronic pain conditions.
All architects and designers have a duty of care to the end users
Under the ARB Code of Conduct all architects and designers have a duty of care to the end users, no matter what their religion, gender or disability. Knowing the needs of the people who will use a building is the most important thing. It’s an opportunity to address varying needs and tailor the space in better way.
There are three neurocognitive profiles that each have differing sensory processing
The three neurocognitive profiles are neurotypical, neurodivergent and neurodegenerative. All these profiles describe the way that the brain is set up, its instruction manual.
The majority of people are neurotypical, but neurodivergent and neurodegenerative brains receive, process and label information in a different way.
Our senses help us navigate our environments
In addition to sight, hearing, smell, taste and touch, we have three extra senses that help us relate to the built environment.
Proprioception – this is our sense of hand eye coordination, essentially where our body is in relation to itself.
Vestibular sense – this is where our body is in relation to the space around us, so being able to sense movement, maybe in a lift moving up or down, or in a car speeding up or slowing down. It’s also the sense that causes car sickness.
Interoception – this is the sense of what’s going on internally in our own body. So being able to sense if you’re tired, if you’re hungry, if you need to go to the toilet.
We have probably experienced a temporary sensory processing difference
If we are drunk, we perceive our environment differently. The speed at which we process is different, the way we speak, how we move, and think is different. Another example is a migraine. Lights may be really bright and sounds really loud, which is our brains processing that sensory information differently.
Stephanie explains that some people with sensory processing differences may experience those things all the time, but it will vary from person to person. If somebody is autistic, they might be hypersensitive to sound, which is why something as simple as a hand dryer going off might cause distress. Visual processing is often different; colours might be perceived as significantly more intense or any high contrast patterns might look like they’re moving so for some people it might look like an optical illusion all the time.
There is no such thing as one design solution fits all
Stephanie says we have a stereotype of autism based on films that show a nine-year-old boy rocking in the corner, who screams if you touch him. Although there will be some people that match that description, autism presents itself differently in each person, with individual sensory needs. This makes designing spaces for the public difficult as it becomes impossible to cater for everyone’s individual needs, so instead we design for the majority of neurodivergent people.
Fixed elements should be muted, natural and calming
By using lower chroma colour palettes we can create lower sensory environments for the primary surfaces. Things that you can’t change easily, like walls and floors, should be as muted and as natural and as calming as possible. You can then add in boldness, in removable features, things that can be changed easily, like a multi-coloured zigzag rug. You can still have feature colours and design elements if you keep them at a lower chroma intensity.
Needs can even change during the day
Stephanie points out that an individual’s needs may also change during the day, with more energising spaces perhaps needed in the morning and then a more calming space in the evening.
Two people sharing one space may have conflicting needs
When designing spaces another consideration is hypersensitivity and hyposensitivity. For some people an environment can be over-stimulating, whilst for others they may require more stimulation.
“As an autistic person, I need complete silence to work, but my brother has ADHD and he is the exact opposite. He can’t concentrate if a room is silent, so if he goes to a cafe where there’s background noise.”
Similarly, some people may require absolute silence to sleep, whereas others need to play music or have some background noise to help them sleep.
We can design for most senses
After our visual sense, smell – or our olfactory sense – is the most powerful in terms of way-finding and navigation. It is possible to design for this sense too. For example by planting scented flowers at different ends of a building, the prevailing winds will carry those scents through.
It is much harder to design for taste. Some autistic children or people with dementia may want to explore their sensory environment by putting things in their mouths. By using low VOC paints and non-chemical materials we can make sure they come to no harm. Similarly with landscape planting, avoid anything that is toxic to humans or animals.
Your home is one space that can be designed to your individual needs
The one space you can control is your home environment. Stephanie shares her preferences, although she stresses that someone else with autism might want something completely different.
When working she cannot stand any noise whatsoever, so her office is soundproofed. She controls the light levels and glare from intense light with light filtration blinds as well as blackout blinds. She has colour-changing lights and individual thermostats in each room to control the temperature depending on her needs.
All the colours she uses are low chroma, with a lower intensity than ‘brilliant white’. Each of her rooms has a different approach depending on the type of energy she needs for that space. When she’s cooking, she needs high energy so having a more energised space helps her.
Sometimes simple measures can improve soundproofing
Stephanie’s own house was built in the 1960s and needed updating. She started by insulating the ground floor, using mineral wool in the sub-floor. Her office has a separate acoustic lining that she put in using acoustic insulation boards.
There are, however, a few simple solutions that can transform the acoustics of a room. Stephanie suggests changing the floor finishes and putting up acoustic noticeboards. Rubber underlay, for example, is more soundproof than other types of underlay. Check out the noise reduction rating of each product. Typically, anything that reduces the sound by 14 decibels or more is going to be a significant improvement. You can also add acoustic absorption through soft furnishings and floor-to-ceiling thick curtains with linings. If you want to go further you can add another wall lining to the existing wall with a small stud frame that you fill with acoustic insulation.
Consulting people with ‘lived experience’ is really useful
It’s important to understand how many different conditions exist and that it’s impossible to know them all. Therefore in Stephanie’s role as a Inclusive Designer, whenever she meets somebody with a disability that she’s not encountered before, she asks them about what would make the environment better for them.
Asking the right questions is important
Meeting people with lived experience of having a specific disability or characteristic is always the best way of learning. Find out about their day-to-day needs, what they find challenging, what they would like to be improved, and so on. Then it is up to the architect to work out how to design the space to suit that client.
Building regulations don’t go into much detail to allow things to get built
Stephanie says that the building regulations are broad and general, because if they were too onerous, it would be difficult to get things built. The main criterion is that all people should be able to use all parts of a building. Everyone should be able to access it and operate everything within it in the same way. That means disabled entrances shouldn’t be put round the back of the building or windows have controls that require two hands to operate them. Touch screens and app-controlled devices for lighting controls are all beneficial.
Part M of the Building Regulations provides a guide on how to achieve this accessibility but it’s limited. Guidance BS 8300 is significantly better as it provides more detail, including the difficulties people have with certain things. For example, rather than it just telling you put an oven at 900 to 1000 mm off the floor, it tells you why you need to do that.
PAS 6463 is a guidance document specifically about neurodiversity and designing for neurocognitive and sensory processing differences. It provides a lot of detail on the issues for people but doesn’t tell you how to fix them. It’s then left to the designer to come up with a solution.
Social media can help you connect to people with lived experience
Stephanie’s top tip is to speak to people with lived experience, because that will be so much more enriching and insightful than consulting guidance documents. Social media is a great tool to help connect with people who have specific conditions and are willing to share their experience. Search using different hash tags.
We could all do better in our approach and the language we use around this topic
Disabilities can be dynamic so on some days a person might need a walking aid, or a wheelchair and then on a different day, they might not be using anything. It doesn’t mean they were faking their condition on the other days. This also applies to neurodiversity, where people can have really good days and really bad days.
Stephanie says that ‘disability’ and ‘disabled’ are not bad words, and we don’t need to avoid saying them. We need to acknowledge that disabled people exist, that they are living in a world that is not designed for them. Typically, disabled people are disabled by the environment, because if the world and all the buildings were set up to be inclusive for everybody, there wouldn’t be as many problems with using the built environment.
Finally Stephanie asks people not to say ‘people are suffering with an illness or condition’. Stephanie definitely doesn’t feel she is suffering; she’s having a great time!
Chris Brookman from Back to Earth explains what wood fibre insulation is, how it could be used on a project and why careful specification is required.
Interview with Chris Brookman
Chris Brookman, founder and owner of Back to Earth explains how his chemistry degree has been put to good use within the construction industry. His experience ranges from working with natural cob to examining the properties of different building materials to create specifications for particular needs. He has built his own Passivhaus and here shares his technical understanding of wood fibre and the many properties it offers for buildings.
Chris working on a cob building
Traditional cob building is strenuous
Straight from university Chris worked as a cob builder. He explains that traditionally cob was a combination of clay, sub soil and straw mixed together by cattle treading over it to make a plasticine kind of mix, that was stacked on top of a low stone wall. These days sands, grits or aggregates might be added to adjust the properties of the mixture. One of the reasons Chris eventually moved on from cob building was because the nature of the work was extremely physical.
Traditional materials can play a part in modern construction
Chris then came across wood fibre, which worked well with cob and that got him interested in learning more about different materials. He was particularly interested in finding materials which have the properties of traditional materials, but are in a modern format, so are easy to use by a modern builder. He eventually moved away from the building business to create Back to Earth, which deals with the specification and supply of materials.
Wood fibre is not just about thermal insulation
For Chris, thermal insulation is only one of the reasons for using wood fibre products. Alongside this it offers acoustic insulation, thermal mass to help reduce summer overheating, and good fire resistance. It is also locking up carbon for the duration of its lifetime, which is really important.
Wood fibre products start with waste timber
As a by-product of the timber industry, the production process for wood fibre starts by grinding up the waste timber to fiberise it, which is then treated in one of two ways.
The wet process uses the natural lignin to bond the product
The more traditional process is to mix it with water and detergents to create a slurry, which is then put on a conveyer belt to strain all the water out, before it is compressed and steamed. Through steaming, the natural lignin glues the fibres together, producing a board around 20mm thick.
The dry process uses a small about of glue
The more modern way is the dry process, which uses a polyurethane-based glue to stick the fibres together. You blow the fiberised wood with the glue, compress it to the right thickness and density before curing it with warm humid air. This creates an homogeneous product, from 20mm up to 200 mm thick.
The dry process makes a lower density product, which is a bit more rigid and has a lower thermal conductivity. However, it massively reduces the amount of energy used to make the product and is slightly cheaper to make. As it only uses a small amount of glue, maybe 3-4%, it has a minimal effect on moisture retention. Most boards are made in this way now and whilst it can be better to use wet processed boards for internal wall insulation they can generally be used interchangeably.
The density of wood fibre can be a benefit over other natural products
Chris explains that he chooses materials based on their properties but, in most scenarios, natural fibre products tend to work better than synthetic materials. Common uses include insulating timber frames, roofs or internal walls.
The density of wood fibre is also a useful characteristic when it comes to adding thermal mass to a building, which in turn absorbs the heat more slowly and can make a big difference to summer comfort. This is one key difference to most other natural fibres.
Building new made it possible to create an accessible home
Chris’ first son was born disabled and it quickly became apparent that the small rooms of their old cob house were not going to work. The house was over three floors with no circulation space for a wheelchair, so they started thinking about building a new house.
A Passivhaus would provide a good environment for his disabled son to stay warm
Chris recalls that John Williamson, in Wales, had just built one of the early Passivhaus projects. He was also aware that when you’re sitting in a wheelchair, your environment needs to be warm.
Bricks from the bungalow are reused as hardcore for the new house
A specialist architect provided input on the designs
In 2011 they found a suitable site, with a 1950s bungalow they planned to demolish and use as hardcore for the new build. Chris explains that they hired a specialist architect to look at their designs and make suggestions about circulation space, door widths and accessibility over the whole site. The whole plot was levelled as a consequence, with just a slight fall to help water drain away, all the thresholds are level.
The office was built before the main house
The office was built first to test their approach
Chris worked on the detailing for the build, but it was a friend who carried out the construction. The office was their test case, and they made a few minor mistakes which meant they were just over the 0.6 air changes per hour at 50 Pascals required to meet the Passivhaus standard. This meant that when it came to the main house they really focused on airtightness.
They used a timber frame filled with wood fibre insulation, which was relatively quick way to build. An airtight OSB was used internally as the airtight layer.
Clay boards were added to the internal walls to improve the acoustics
In a Passivhaus you need to have a little gap under the internal doors to help the air flow, but that can cause issues with sound transfer. So Chris used clay boards on all the internal partitions to improve the acoustics.
Where structural, the internal partitions have Fermacell on one side and clay board on the other. The non-structural partitions have clay board on both sides with flexible wood fibre in between.
The clay boards have given the added benefit of increasing the thermal mass of the building, so help to reduce summertime overheating.
All new builds have a few niggles
Chris and his family are really happy with their home but there were few things aspects they were keen to address. The biggest mistake they made was with the front door, where they cut a metre wide opening into the frame, but hadn’t realised the thickness of an external Passivhaus door. So they ended up with an opening width of 740mm which made it difficult to get in and out with a wheelchair. This was, however, changed a few years ago so now they have a 1300mm wide opening.
They also swapped two of their clerestory windows to ones with electric openers to make it easier to purge ventilate in the summer. Chris had initially thought the MVHR system would be able to deal with this but it wasn’t enough on its own.
Something that couldn’t be changed without substantial work was the liquid screed floor finish. They had intended to use underfloor heating tiles, but they were too expensive, so they used liquid screed instead. Chris regrets this choice as this floor transmits sound right across the house.
One other regret was connecting the house to the gas main. Not only was it expensive to install but at the time grid electricity was about 500 grams of CO2 per kilowatt while gas was 180 grams of CO2 per kilowatt, so using gas to heat the home seemed like a good option. Chris may well switch his heating source in the coming years.
Back to Earth’s specifications ensure their materials will give the right results
Chris sees the primary role of Back to Earth as creating specifications for materials to ensure they achieve the best results on each construction project. Most of their work is on retrofit projects and they use WUFI to model the specifications they are producing.
A WUFI analysis of a specification
Chris sees them as problem solvers, looking at specifications to provide the right material for a particular function. His own construction experience also means they can add in practical details alongside the specifications.
The Fibres Academy training platform
Chris believes a lot more people would use natural materials if they understood them better. To that end, Back to Earth have just revised and relaunched their Fibres Academy training platform. This is free to use and gives you access to courses, 3D model and installation guides to help you use the materials with confidence.
Chris tells us that Europe is a long way ahead in the amount of natural fibre materials that they use. Figures from a few years ago showed Europe’s use of natural fibres at around 10%, whereas in the UK we’re struggling to reach 1% of the market share. There is a fundamental difference in perception and accessibility between the UK and Europe. Back to Earth’s training platform is trying to improve people’s understanding of the products to increase use and push forward this agenda.
Generally as a share of the market, Europe is using about 10 times more natural fibre than we are.
Natural fibres are generally a bit more expensive but worth it
Natural fibre products may be slightly more expensive, but for Chris it is like comparing apples with rotten eggs. People might say why use wood fibre instead of PIR? But often the installation of PIR isn’t good. It may just be wedged between timbers, resulting in air gaps opening up later and reducing the performance.
So often the perception is that modern materials are cheap, but this can be because the time is not taken to install them correctly. Back to Earth give detailed guides, going through all the airtightness layers and the whole build up. This ensures correct installation so the product works.
It’s also important to recognise the value and added benefits that you get with these materials. It’s not just about cost, there’s the environmental impact, the health of the installers and the health of the occupants years down the line, along with the longevity of the building and the finishes.
A change in attitude and better regulation is needed in the UK
Chris feels we have a different attitude to our housing than the rest of Europe. We’ve commodified housing, so we buy and sell with the expectation that we will make money from our properties. If people actually proiritised comfort and health, they would probably steer clear of major developers and make different choices.
The building regulations also have a role to play in increasing the use of natural materials and better legislation from the Government would have a big impact. Government should not be a passive overseer, but be there to guide people’s activities, which could make a big difference in the emissions from the construction industry. This could include an assessment of the embodied carbon of products and the biogenic stored carbon. The locked-up carbon in wood fibre, may only be for the lifetime of the product, but surely that’s better than it not being locked up now.
Toby Diggens explains what it takes to meet the requirements of the Living Building Challenge, and working to the standard when renovating an existing building.
The Living Building Challenge is a holistic framework
It aims to create a building which is as closely tied to its ecosystem and surroundings as possible. It’s not about delivering a ‘slightly more sustainable’ building than standard building techniques. It considers how a building exists in its ecosystem, and how it can be made positive to that ecosystem, rather than neutral or negative. While the framework includes things like a ‘red list’ of materials that you can’t use, it’s about far more than the science and technology of the building construction.
Another aspect to the framework is its ‘offsetting’ concept. Because Toby wanted to develop an existing building, that reduced the offset required. But the concept also factors in the type of land being developed, and the rural farmland ‘zone’ where the barn stood meant some dedicated ecological restoration was also required.
The barn before the conversion
The standard is challenging, but offers flexibility
Renovating an existing building does add some complexity to the Living Building Challenge. The superstructure of Toby’s barn required breathable building fabric solutions, so effectively pushed him towards a more ecological approach anyway.
Another reason that Toby chose the standard over Passivhaus or BREEAM accreditation is that it gives you the opportunity to argue your case for decisions made. You have to meet the general principles of a modern ecological building, but can also justify why you’ve chosen a particular detail or bought a particular product.
The balance between traditional construction and modern building regulations is interesting
While there are few buildings accredited to the standard, humans have a long history of dwelling on the land and developing traditional building techniques to create shelter. The complexity of the Living Building Challenge comes from ‘fast forwarding’ those traditional techniques to make a modern building. Toby found he was able to hold to traditional principles throughout his project, and it really spurred him to think about details – even down to recycling the materials that came out of the building.
Sometimes compromise is necessary
Only one material choice prevented Toby’s project from using all ecological materials. Expanded polystyrene (EPS) insulation was required under the concrete raft floor slab, because a suspended timber floor with natural insulation would have impacted on the overall volume of the space and reduced the upstairs floor heights too much. The mitigation for the insulation choice was that the raft slab itself used recycled fly ash concrete rather than virgin concrete.
The Living Building Challenge was a positive towards achieving planning permission
Several factors helped Toby to achieve planning permission. An application had previously been refused to turn the barn into holiday lets, so it was good that Toby could show the conversion would be a place for him to live and work. In an area where many people commute to Exeter, it was a significant positive to be applying for something that would create community and support local farming activities.
A ‘living building’ includes aspects of biophilic design
The Living Building Challenge references biophilia throughout its literature. For Toby, biophilia was an integral part of the design process. He had always dreamt about having somewhere in a house with a big-enough glazed area to grow plants, and the barn’s structure allowed him to create a double-height atrium.
But biophilia is more than just plants in the home. It also means designing as if your environment is your outdoor environment. The ‘flow’ of a place creates a calming environment as much as function does. When it is done right, it’s very aesthetic because it makes you feel right about your surroundings.
Trying to do the project quickly could have led to bad decisions
Toby avoided aggressive timescales, which helped in terms of managing costs. A faster timescale would have needed more people or more materials on the job, and costs would have gone up. He also feels it was important to see the design emerging and then decide what next, rather than forcing solutions onto an old building.
Extra time also allowed the opportunity to analyse the project’s finances and see where any design decisions might need to be changed. A key learning point for Toby is that there is never one way to finish a project. There are lots of ways around challenges, if you have the headspace to think things through and design a solution.
Setting your stall out is essential for creating an ecological building
Toby was clear with everyone involved on the project what he wanted to achieved, and that there could be no corner cutting. For example, a stone wall fell down and Toby insisted that it be rebuilt in the way it was originally built. His builder was incredulous, but days later was photographing it as something he was really proud of.
The logic of sourcing materials locally simplified things, in some ways. The barn features a lot of ash, because local woodland was being cut down to try and get ahead of ash dieback. Toby has friends with a company that uses native hardwoods, and they helped him to get the ash milled up. It really contributed to the feeling of the house being tied to its local landscape.
Managing waste led to interesting design solutions
As part of briefing the team clearly, Toby asked that larger offcuts and scraps of materials be saved rather than disposed of. Most people would see such collections of material as waste, but they were a resource for the project team. Design details emerged from having this collection of materials, and there were occasions when the team could marvel at what had been achieved out of a pile of ‘waste’. It took a lot of work to keep people focused on this, but it led to a lot of satisfaction with the finished result. And during the project, Toby never had to hire a skip.
Being a working farm also helped in terms of managing waste. Pallets are now used for storing hay on, and there is always a use for offcuts of timber. Local farming department stores have schemes for recycling silage wrap, so Toby was able to give them the plastic wrap from insulation and other materials.
Keeping momentum is essential – and can require some ruthlessness
One of the main things Toby has learnt is that momentum is everything. If you lose it, regaining it is very difficult. As part of project managing his build, he found he had to be ruthless in keeping stuff arriving to site and keeping people engaged with jobs that moved the project on. He worked hard to make sure people were well-briefed, had the right drawings in front of them, and that he able to answer any questions about any details.
The water requirements for full Living Building certification are demanding
Toby hasn’t achieved the drinking water requirements that need to be met for full accreditation. He would have to spend £20,000 or more on a tank to collect rainwater, and a UV filter. He would like to use his own water rather than the mains, but a mains connection will always be required to provide a top-up if required. If money was no object then he would install the system to get full ‘Living’ certification, but the project can still achieve ‘Petal’ certification.
A log burner is allowed by the Living Building Challenge
In his rural location, Toby has a sustainable source of wood to fuel a log burner. The Living Building Challenge views this an acceptable ecological approach, as it ties in to management of the land. Also, compared to a densely populated urban scenario, a log burner is not very damaging from the perspective of particulate pollution.
As well as the log burner, Toby has electric underfloor heating, but it hardly ever comes on because of how well insulated the house is.
Living Building certification is awarded only after as-built checks
Design details have to be submitted, showing things like the thickness of insulation, and an airtightness test is required. Energy use over a year is also submitted.
The version of the standard that Toby worked to required the house to be able to produce 105% of its energy, for which he has a solar system and a Tesla battery, as well as solar hot water.
Retaining character in old building means looking at features you’ve already got
It can require some foresight, but developing a design around existing features really helps with keeping character. For example, Toby had a strange opening in an existing wall that had a lintel about 12 feet off the ground. He was looking for ways to form a doorway without causing the wall to collapse, and suddenly looked at the opening and thought about making that the door. So now he has a 12-foot-high door with an original oak lintel.
Creating a ‘living building’ is a massive undertaking
Toby can’t see the Living Building Challenge exploding in popularity in the self-build community. While it is a wonderful concept, he sees it as something better suited to bigger projects where there is more resource available for project management and dealing with accreditation. Many self-builders already make such a lot of sacrifice, perhaps living in a caravan on site while a project progresses. It’s very self-willed to achieve the most important things of getting the project finished and getting into the house. You have to be exceptionally committed to also achieve all the targets of the Living Building Challenge.
Janice Gardiner, an ecologist and the client of last week’s interviewee Josh Wood at Green Trace Architect, is here to tell us what it is like to be the client on a Passivhaus project and share what she has learnt from the experience.
Interview with Janice Gardiner
Janice Gardiner is a nature conservationist and alongside her husband Colin has created the beautiful Hazel Tree House. After having their youngest child leave for university, Janice and Colin decided that they wanted to downsize from their 4 bedroom, victorian terrace house in North Somerset and embarked on the adventure to build an eco home in the Herefordshire countryside. After moving in just over a year ago, the house is living up to all of their expectations and even surpassing them, after recently winning the Best Eco House at the Build It 2023 awards.
In this chat, Janice talks about what it’s like to be the client in a Passivhaus build and shares with us all of the lessons she has learnt along the way.
Finding the site
Janice and Colin had been looking to downsize and originally their search had included houses or renovation projects in the area close to Ross on Wye. But when they discovered a former pub garden with outline planning permission, they began on the new-build journey instead.
“We’d done up a victorian terrace for 20 years, so we were constantly looking after the house and making improvements. So we actually want a house that will look after us.”
The site is just under an acre in size and includes the house plot, overlooking an orchard and also a field behind, that Janice is using her knowledge of wildflower meadows to manage.
“We’d always looked at Grand Designs and we’d always thought we’ll never do anything like that. And I think it was just seeing it in a place that we were considering we just thought well, let’s have a look and see what’s possible!”
Start with clear intentions
As an environmental conservationist and ecologist, Janice states that it was always going to be an eco-house; in the materials that it used and level of energy efficiency. Although initially they thought that they wouldn’t be able to stretch the budget to meet Passivhaus standard, there was an ethos of sustainability from the start. Having this clear intention allows you to create a team that possess the knowledge and skills that are in line with these values and will provide a strong structure for your build before you even broken ground.
“We wanted it to be eco so that was one of our criteria to start with. My backgrounds in nature conservation, so the environmental side and the ecology side was very much there. Then because we knew we wanted an eco build, we started looking for architects that had those credentials.”
It is crucial to find the right team
Because Janice and Colin began the process with clear intentions, they were able to assemble a team that had the same shared values and the qualifications to put them into practice. Being from around the Bristol area, Josh was recommended to them by another firm and they began the talks with him.
When it came to finding a crew for the actual build, Janice was able to draw on the large community of eco builders in Herefordshire and as a result found Dai Rees, a local Passivhaus builder. He was the project manager and the main contractor, and having his expertise working alongside Josh’s designs helped the build run smoothly. The team he put together was also quite special as they were all builders who had an interest in Passivhaus and eco builds, so were eager to learn and put their own special touches into the house.
This strong team shows that the overarching ethos of a build will help you find people who share those interests, and through their passion for their work you will together create something really special!
“I think you should try and enjoy the whole process and I think there’s something about working with people that you have a good relationship with. What I found lovely about doing an eco build is that because people are doing what they’re interested in, you’re all trying to achieve the same thing. There’s a bit more of a meaning behind it for all concerned.”
The planning stage is not to be rushed
At the beginning of the build, they didn’t think they had the budget to build to Passivhaus standard. Josh then came on board and was able to not only provide the design and technical drawings, but also present the different build methods and materials that could get the house close to that standard. An architect acts to guide clients through the sea of information that can be overwhelming if you haven’t done this before.
Josh provided Janice and Colin with an excellent feasibility study that helped them see the larger picture in relation to their site, planning and construction methods. They also sat down and identified what characteristics they were looking for in their house; how they wanted to live within it and how it would make them feel. The exercise highlighted that Janice and Colin wanted a modern but modest eco home which promoted simple living with a sense of joy and calmness.
“I think he was then our guide as to the method of construction and all of the design of the house. But he did a really good feasibility study with us in terms of what it is we wanted and how we wanted to live”
Planning restrictions can be a license for creativity
Within the planning permission for Hazel Tree House there was a restriction that it couldn’t be larger than 100 metres squared internal floor space and limited the house to two bedrooms. This meant there was a need to creatively design the space to get the most out of the size restrictions. Josh was able to work within these limitations by including a void area over the open plan living space that allowed for the house to feel bigger without going over the floorspace restriction. In addition, the upstairs of the house is situated under a pitched roof, and within planning regulations anything that is under eaves that are lower than around 1.5m is not included in the floor space calculation. This restriction ultimately led to space being used as efficiently as possible and added features that maybe wouldn’t have been considered without it there.
Outline planning permission can offer a lot of freedom
At outline planning the previous owner had not submitted a detailed plan for the build and as result there was a very standard outline of a two-bedroom house with 100 metre square internal floor space but no other details that were specified. This meant that they had quite a lot of freedom in terms of design and style as long as their new plan met these guidelines. This included moving the overall position of the house further back in the plot, in order to save a large Hazel Tree from being removed, which later became the design inspiration for the house, a crucial factor in keeping the house cool in the summer and the house’s namesake.
The build system
Hazel Tree House is constructed on an Isoquick raft with a poured concrete slab. It is a timber frame structure using I-joists with walls made from blown cellulose insulation sandwiched between wood fibre boards. The roof and half of the external walls are clad with black corrugated metal with integrated gutters and the other half with cedar panels. The windows and doors are all triple glazed from the Green Building Store and the internal walls are finished with clay plaster. Due to the very efficient way that materials are used, the house has a negative embodied carbon score.
Due to delays in planning as a result of the Covid-19 pandemic, the whole process took a total of 2 years, from buying the land to moving in, but the build itself only took 9 months of that time.
Where to save and where to spend – bespoke vs standard features
Janice talks about how you may start with the simplest design intentions but when you are given other options that are maybe a bit more interesting but add to the cost it is difficult to not be tempted. The pay off is in what they offer you or the joy they give you.
“A straight A frame shape would have been your simplest form and your cheapest form. Josh came up with the idea of lifting part of it to create this opening and this veranda. Once you’ve seen that, it’s very hard to just look back. So I think that is the thing that happens. You’re on a creative journey with your architect, and then with your builder. Some of the joy of the build is in doing those things, rather than sticking with just what you’ve said and just what the budget is maybe dictating. So I think your personality comes through in the decisions you make there.”
Janice shares that Hazel Tree House’s signature round window added expense to the project and caused a few headaches when it came to installation and the creation of an external window sill. When building a Passivhaus, airtightness is crucial and unusual shaped windows can be areas where gaps can be created. There are ways to avoid this and with some bespoke and creative carpentry, solutions were found. Janice says that despite the added challenges that the round window created, she is very glad they decided to do it as it is very worth it for the character it gives.
The tin cladding is actually an example where Janice and Colin decided to save money. They had originally looked at dark grey cladding panels which were significantly more expensive than the black corrugated metal they ended up choosing. But in fact, the cladding that they decided to go with adds a beautiful structure to the back of the house and hints to the agricultural buildings that it shares the landscape with. This is an example of where the more expensive option may not be the best for you, and it is aways good to refer back to your intentions for the build: does the material or feature align with them?
“We did stretch ourselves because the things that we said we can’t afford, like the solar panels and Passivhaus certification, were things that we really did want to do and we really did want that quality of finish. So, I think you can say to yourself, I’m not going to do it. But actually, once you’re doing the build, and really involved in that process, you’ve got to be very strong to not go with what your heart actually wants.”
Is Passivhaus certification worth it?
In the case of Hazel Tree House, the aim had always been to get it to the highest standard of energy efficiency that they could, including an MVHR, triple glazed windows and a very high standard of blown cellulose insulation. It was only during the build that Janice and Colin decided to go the whole way and get the passivhaus certification as well. This is not an essential extra step and in essence whether you have the certification or not, your home’s performance will be the same. But for Janice this final step felt like the perfect end point: once you have gone so far, why not go the whole way. It is also good to be able to actually monitor the performance of your house for resale purposes and because it is nice to know that extra effort in construction has been worth it. In this case, Josh was able to use Hazel Tree House as the basis to get his Passivhaus designer qualification as well.
Not everything will go to plan
Janice and Colin encountered their biggest challenge of the build whilst laying the concrete for their foundations. The site access already limited the size of the vehicle that could deliver the concrete and although two trucks had been arranged to deliver the concrete in rely, only one had been sent. To add further insult to injury, when the truck returned, the plant had broken down and they had to go to one further away. When working with concrete, time is of the essence, and the way it is laid can impact the finished outcome. As this concrete slab was also going to be polished and become the floor for the whole of the downstairs, it was even more important that it was done properly and due to the delay, the team stayed late into the night to work on it. This issue did ultimately impact the finish of the floor and there are areas with imperfections, but as Janice points out, these things are quite quickly forgotten about or overlooked once the build is over and you move into the house.
The client experience during the build
Janice lived in a bungalow close to the site during the build so was able to be present on site pretty much every day. She describes this as a great experience as you get to see all of the stages of the process and really feel a part of the journey. She also highlights an interesting flip that you see as the client. For the first half of the build you are watching; because the builders are following the architects plans, you have very few questions you need to answer. But as soon as the internal finishes begin, you start to be asked questions that you haven’t even considered yet. So as a client, the internal structure and design of things such as lights, sockets, stairs, doors, kitchens, bathrooms etc is the area where you will be most in demand.
“You sort of get used to not really having very many questions, or just having a look at things, maybe you’re looking at the windows and stuff. Then suddenly it comes to the internal and ‘Oh, where your stairs going? What stairs do you want? What’s your electric? Where do you want your sockets? Where’s your lights?’ and suddenly, you really are in demand and having to make decisions. You know, really thinking about the internal layout and structure, when you haven’t even got walls necessarily.”
Visiting another house can be an amazing way to understand what you want for your home
All of Hazel Tree House’s internal walls are finished with clay plaster which creates a beautiful and warm textured surface. Janice says that during the planning stage they were able to visit another passivhaus in the area (Old Holloway) who had chosen the clay plaster finish and fell in love with it. Not only does clay plaster create a beautiful effect, it also good for the overall health of the building as it is a natural breathable material which will take in moisture when there is an excess and release it again when needed. The clay plaster can be a good choice too if you are looking to reduce the upkeep needs of a house, as once it is sealed, it is a finished surface that won’t need to be repainted every few years like other wall surfaces.
Being able to see the finish in person really helped them feel confident in their choices and now that the house is completed, Janice and Colin have participated in the Passivhaus open day for visitors who are beginning their journey, to share what they have learnt and help them with those decisions.
“It’s a big part of the finishes getting the clay plastering done. But then it’s done. You know, you don’t have to paint unless you choose to. So basically, once all the plastering is done, that’s it, your house is decorated.”
Adaptability and problem solving is crucial
Having a good builder is very important, as their ability to alter plans and adapt to certain situations is crucial. There were a few occasions where Dai was able to highlight a potential problem and come up with an alternative option or an added precaution that helped to avoid big disasters. One example of this was with the Air Source Heat Pump that was fitted. Because of the size restrictions from planning, Hazel Tree House has what Janice calls a “mini plant room” which is essentially just enough space to fit everything in it. When Dai and his team were constructing the walls Dai pointed out that once the Heat pump was in place it would be very difficult to get out again so he decided to create a removable panel instead of a wall, which would be there in case it broke down. As luck would have it, the heat pump was delivered faulty but this fault was only discovered after it had been installed and turned on for the first time, and Dai had to use his removable panel to get it back out again.
“I think that was the lovely thing about the design process, your builder is solving problems and coming up with solutions all of the time. We have a strange shaped downstairs shower to fit in a very compact space, which caused a bit of headache: how am I going to make a shower tray here because I can’t buy one (unless you want to spend a lot of money). So it’s those things that you’re solving as you go with the help of very, very good builder.”
Open plan living
Hazel Tree House is designed to cater for open plan living and the main social space of the house contains the kitchen, living room and dining room all as one. Janice describes it as a lovely space where you can all feel connected, even if you are doing different things, with also the option for private spaces in the bedrooms and office area.
“It was lovely last Christmas, we had all the family here. You could be cooking and still part of everything that’s going on and that felt exactly what we wanted. Then if you want private space that’s either coming to bedrooms, as a separate space, so we do have a chair in our bedroom. And then an office space that is more functional and actually can be more messy. You can keep the mess out of that sort of central social space and I think it very much functions like that.”
Performance – “You have no concept of what it is like to live in a Passivhaus until you have lived in one”
Janice talks about how she knew that a passivhaus was going to feel very different from a standard house, but was unable to comprehend the realities of that until after they had moved in. The key thing she highlights is that in a standard house, you have warm rooms and cold rooms, so to move within your house you are constantly changing from one to another. In a passivhaus the temperature is constant throughout the whole building, which make the entire house feel more liveable at all times of day and all points in the year. On the day of recording in December the house was 19 degrees centigrade in the morning (after a night which dropped to below 0).
The house has solar panels installed and uses the electricity to heat the hot water tank and power the lights etc. The house only has two towel rails and finds that most of the heat in the house is generated through sunlight, cooking and just generally moving around. The solar panels feed into the grid and are not connected to a battery as this was an expense that the budget couldn’t stretch to, but Janice hopes to get one installed in the future.
“We are very geeky about it because we do constantly monitor the internal and external temperatures, we have monitors all over the place. And you have to learn to manage it as well, I think, because it is so different and so new. It was 19 when we woke up this morning, and it’s gone up to just about 20, just from us being here and having the oven on a bit… What we’re finding is it drops one or two degrees overnight, because it’s not 100% efficient in keeping the temperature in. And then in the evening, when you’re sitting down more, that’s when you might want to have a bit of heating on just to boost that temperature. And we just use, an electric heater and we have the towel rails, but that is all that we’re pretty much using.”
Is it luck or is it having an open mind?
Janice highlights that it was a relatively smooth build, and they didn’t have any major issues. There were things that went wrong, like the concrete plant breaking down when you are in the middle of laying the base slab or the water heater being delivered faulty and having to be replaced straight away. But the overall feeling is that these things are what you make of them. Janice talks about her build with positivity and an overall sense of enjoyment, so whilst it may feel like luck, your own mindset and flexibility is a crucial factor in any project.
“It has gone really, really well and I think knowing we wanted it to be an eco house helped from the start, because then that’s what we were looking for. And to some extent, you can say we were lucky to come across the right people, but I think it was then just trusting your gut about how you got on with someone because that relationship is something that’s going to go on for nine months. I think it’s probably very important, because it’s a process you’re all going through for that length of time.”
Ludka and Brendan Powell explain the Welsh ‘One Planet Development’ scheme and how it led them to building an off-grid, straw panel Passivhaus.
Interview with Ludka and Brendan Powell
Ludka and Brendan Powell are self-builders with an interest in sustainability. They began to question whether the way they were living was the best way to live, and could they find an alternative way that connected them with their surroundings more.
One Planet Developments (OPDs) are a Welsh Government initiative
By granting planning permission to build on agricultural land, the scheme aims to get people back to living and working in the countryside, growing food locally. A One Planet Development means living a sustainable lifestyle, with the lowest carbon footprint you can manage, producing your own power and dealing with your own waste.
A key goal is to ultimately produce 60% of your own food on site, as part of meeting your ‘basic needs’ within five years. Basic needs include council tax, running a car, phone bills, and the food that can’t be produced on site.
Meeting the five-year goal of an OPD requires a business plan
It’s very difficult to quantify how you’ll be doing after five years, so the scheme requires that you have a business plan and produce an annual progress report. At the end of five years, if you haven’t quite reached your targets but are on the right track then you produce a second business plan to show what will happen next to reach the goal.
At the halfway stage of their own five-year timeframe, Ludka and Brendan have found it to be a big ask but they are on schedule. Anything they overproduce helps with their income. For example, they sell salad to local shops and make sauerkraut from cabbages, alongside producing honey.
One planet thinking is long-term, holistic thinking
An important part of the OPD is that Ludka and Brendan are trying to regenerate the land by transitioning from monoculture. They are trying to bring biodiversity, grow crops alongside keeping animals, and farm organically.
They have planted an orchard and an extra acre of woodland to attract wildlife, and keep bees to help with pollination. It’s about working with nature rather than being geared towards profit, and the real benefits might not be seen for a decade. It is about attaching other values than just a monetary value to things.
The one planet way of life is sustainable
Doing everything in five years is a massive challenge, and Ludka and Brendan acknowledge they might not be doing everything right straight away. However, they are confident that after ten years everything will be perfectly fine.
It is sustainable in the way they are putting a lot of energy into the land, but getting so much back from it in terms of fulfillment. As well as seeing the productivity of the land improve, they are also seeing change in terms of people being willing to go out of their way to buy produce from them rather than from the supermarket.
OPDs attract determined people
Building a house is often the biggest thing anybody undertakes in their life, so doing that alongside regenerating a piece of land and building a sustainable business has been intense for Ludka and Brendan. Taking on a self build is not the only route for those undertaking OPDs and some opt to build tiny houses using the Caravan Act. However, for Brendan and Ludka it was an opportunity to create more space for family life and have a hardy kitchen for processing their crops.
People who do OPDs tend to really care about the planet’s future, and recognise that we can’t carry on living as we are. There has to be different way.
One Planet Development Policy can evolve
OPDs are an experiment to try and take society in a better direction. There are not many of them, but the existing developments have been successful in feeding people locally and improving the ecology of the land.
Not everything in the scheme is perfect but it gets reviewed and recommendations for improvements have been made.
Being off-grid is not mandatory for OPDs
Ludka and Brendan have no utilities coming to site. Their water comes from a borehole, and electricity is generated from solar PV. Waste is dealt with through a composting toilet and reedbed system.
Anyone creating an OPD can choose the most sustainable solutions to suit their site. Using mains water is not really a problem, but one of the principles of the initiative is dealing with your own waste.
Off-grid living is more mindful
The project is labour intensive, even more so because Ludka and Brendan also have three children. But it also makes them more self-reliant and aware of their actions. They can’t just switch on the electric oven at nine o’clock at night in December because they want to heat something up.
Their children are growing up with the same values. For example, if they have a bag of sweets, that creates plastic waste. What will happen with the waste? They don’t have a throwaway culture.
That extends to the household waste and their sophisticated composting system. In a ‘normal’ house it’s really easy to just flush the toilet and not think about where the waste is going. Ludka and Brendan have to constantly think about what they’re doing with their waste and keep an eye on everything.
A Passivhaus was the natural choice – in more ways than one
Having lived in a cold and damp house that was never truly comfortable, Ludka and Brendan knew they wanted a house that was going to cost very little to run and not need lots of heating.
Making it as well-insulated as possible meant they wouldn’t be spending time on the land sourcing firewood to burn. In their temporary accommodation they were burning wood all day and half of the night in winter; now they only need enough to make dinner on the cooker, with enough residual heat to heat water.
One Planet living means using sustainable and natural materials where possible, and minimising your carbon footprint – so a timber-framed Passivhaus with straw bale insulation minimised both operational energy and embodied emissions.
The straw bale system performs as promised
Getting a straw bale house to Passivhaus standard is difficult, but the EcoCocon system has delivered what was promised. The addition of wood fibre insulation around the outside brings the insulation up to the required level. Once the system was in place, it was simply a matter of following all of the normal Passivhaus principles to achieve the necessary airtightness and so on.
The wraparound veranda helps the house stay cool in summer
A veranda provides shading that is at just the right angle to maximise passive heating year-round without summer overheating. The veranda is also somewhere to live outside in the Welsh climate.
In the summer, the windows never need to be opened because Ludka and Brendan never feel they need to do so. And in autumn, they were amazed at how warm the house continued to be when the air temperature outside started to cool.
During winter, the sun shines through the windows and warms the polished concrete floor, which helps to keep the house warm until the following day. And the floor was a practical choice too, because it’s easier to sweep when bringing in mud from the fields.
Making careful material choices throughout
Yet another advantage of the concrete floor is that Ludka and Brendan didn’t have to buy carpets or wood flooring.
Keeping within the One Planet principles, they have used recycled materials wherever possible – including recycled foam glass in the floor, and cellulose (recycled newspaper) in the roof. Sourcing local materials was also important. All of the cladding was made within ten miles of the site, and all of the architraves are made of local ash.
Inside, they’ve used a kitchen recycled from another house, and done similar with bathroom and utility room fittings – all of which helps to save money too.
MVHR can work in off-grid houses
Ludka and Brendan’s MVHR system uses very little power, around 20 to 30 Watts all the time. On a few days in December and January, when there’s little light, they’ll only run the MVHR in the day. There’s been no detrimental effect from that.
They run two inverters, having fitted a smaller one that can cope with demand from the MVHR, lights and laptops. The larger inverter is still needed for appliances, but it was using over two kilowatt hours per day by itself. Using the smaller inverter means they can now more easily survive the winter without getting short on power.
Running businesses together helped with teamwork
Both Ludka and Brendan were very engaged with the project, rather than one of them leading. Both have been involved right from the ground up, but they would feel strongly about different things. The important thing was to ask each other’s opinion.
Through running businesses together they have learned to delegate, so Ludka wouldn’t deal with carpentry but did do a lot of wet processes like clay plastering. Plasterboarding and decorating ceilings were two jobs in particular that provided to be long and laborious!
Creating a One Planet Development requires strong-mindedness
You have to be resourceful and dedicated. Never underestimate how much there is to do, but never give up. There is a solution to everything, and Ludka and Brendan have found they’ve become really good at researching and solving problems.
Projects don’t go the way you want them to, and you have to continuously pick yourself up from failure, but somehow it all makes sense in the end. Creating an OPD has brought a sense of integrity to Ludka and Brendan’s life, as well as a sense of community from within the One Planet movement itself.
Now, he has a new book: Natural Building Techniques – A Guide to Ecological Methods and Materials, and it is topics within that which we have been discussing with him. His book includes sections about renovating and retrofitting, information about suppliers, and different kinds of natural materials that are available. It also looks at some recent case studies, talks about how to tackle projects, and what some of the obstacles might be that you could come up against.
The supply chain of natural materials is becoming far more robust
Tom explains that for a long time people have been given excuses about why natural materials are too expensive or don’t work, which has acted as a barrier to their take-up.
However, in recent years, a lot of work has been done to make the supply chains more robust, with greater availability and, in some cases, cheaper pricing. This in turn has encouraged more people to try them.
Tom also believes that new fire and thermal performance regulations will make it harder for plastic and synthetic insulation companies to fabricate results, and composite materials like hempcrete will be shown to be just as good.
The term that is generally used for natural materials is bio-based materials, which covers anything from timber and straw, to hemp, sheep’s wool, and other natural fibres. Closely linked are also things like earth and lime.
We need to stop using timber carelessly
When it comes to the sustainability of using natural products, Tom addresses the current problems with timber.
“There’s enormous amount of wastage of timber really. Timber is used in many situations, where it probably isn’t needed to the extent that it is, but people just chuck it in as though it’s a cheap material, which it no longer is.”
He also says that there is a lot of misinformation around the flammability of cross-laminated or mass timber construction, which has resulted in people returning to use concrete.
We do though need to be careful and responsible in our use of timber, and Tom explains that there are companies in the UK that are constructing using locally harvested roundwood poles, which is a great way of using timber more responsibly and economically.
Tom also suggests that there are many more resources that remain untapped, for example the biomass waste from palm oil trees could be used for bio-based composite products.
Lime and clay can be great alternatives to cement
Tom has been working with lime for a number of years and says that it is a natural biocide which is very good for healthy buildings. It does however still use energy to produce it, so he is now experimenting with a clay powder that seems to work almost the same as the lime, and which would save a great amount of embodied energy.
Stone and earth are two of the oldest forms of building material
Stone is a natural material that can be re-used and Tom is horrified when he sees sites being bulldozed and the stone being buried, when there are far greater benefits with the many other ways it could be used.
While cob and rammed earth have plenty of advocates, using these materials alone it can be hard to reach modern standards of energy efficiency. However, they are hygroscopic and have health-giving properties that make them a very good material to use.
Tom is a great believer in hybrid construction these days, and building with timber, sheep wool, earth, hemp and all sorts of other things, depending on what’s available and how they can be combined together.
Straw can be tricky if you don’t know what you’re doing!
Tom admits that he’s not the biggest fan of using straw as a construction material, largely because he’s seen so many straw bale disasters!
People often think because straw bales are relatively inexpensive, then it must be cheap to build a straw bale house and anyone can do it. However, there are a number of pitfalls, such as when you have a roof resting on the walls you need to factor in that bales are going to move, their suitability in very wet conditions, and having to be extremely well rendered and plastered to make them safe from fire.
He has however seen some wonderful examples, particularly when the straw bales are used as infill within a timber frame, rather than being load-bearing.
If you are looking to build with straw, Tom recommends getting experience first on another project so that you know what’s involved, and preferably attend a training course run by experts.
Hempcrete is an excellent material for managing moisture in a building
This would always be Tom’s preferred method of building, used as 300-350mm walls within a timber frame construction. It has an impressive thermal performance and also creates a very healthy environment because of its hygroscopic properties.
Over the last year, they have had a study done by the University of Ulster on one of their hempcrete buildings. Despite temperature and humidity levels varying greatly throughout that time, the relative humidity stayed exactly the same.
It is also very versatile in its application. It can be mixed in a mixer and cast in shuttering, it can be sprayed into a building, and it can also come in block form.
Hemp is readily available for use in construction, with more growers jumping on the bandwagon of bio-based materials for company carbon off-setting. It is a useful crop for farmers because it’s used in the annual rotational cycle between cereal crops such as barley and wheat. The fibre is stripped from the hemp and this in itself becomes extremely valuable. The hemp fibre can be used in a variety of insulation products or composites, including car interiors and replacing plastic in aeroplanes.
Emphasising eco-credentials can make mortgaging more challenging
Tom thinks that sometimes approaching insurers, mortgage providers, planners, and building control professing your wacky eco house ideas can be detrimental!
He suggests that by being more tactical and not making a song or dance about it, you’re less likely to have a problem. He gives the example of a small company in Wales who have just sold a trial hempcrete house, which got a mortgage from Nationwide Building Society without them batting an eyelid.
“It’s no good just saying, Let’s insulate it”
With his book, Tom is keen to educate even some of the green movement who emphasise the importance of insulating all the buildings in Britain, while effectively promoting the use of petrochemical insulation materials.
“There must be lots of white van men out there just happy to come and stick any sort of plastic rubbish into buildings. That is not good enough. We have to get people to use the right materials and the right techniques that aren’t going to damage the planet and aren’t going to damage people’s health.”
He accepts that there will always be some things that can’t really be made out of anything other than plastic, and if they’re used in a sparing and limited way then that’s something that shouldn’t be condemned. However, he takes issue with some of the Passivhaus organisations for promoting materials that are plastic and synthetic oil based, which they are claiming will help to save the planet by reducing energy. When 50% of the plastic waste going into the oceans is from the construction industry, Tom questions why they need to be wrapping buildings in plastic membranes, when we can build airtight buildings with hempcrete that are fully breathable and aren’t wrapped in plastic.
Active House provides an alternative to Passivhaus
Tom sees Active House as having a more holistic and sensible approach to these issues, particularly around the design and configuration of buildings, use of daylight, passive solar etc. The Active House Alliance has recently been set up in the UK and certification will be offered in the future.
We don’t have enough building performance data
Tom is keen to see far greater investment in building/material performance data, but says that while organisations such as Innovate UK have thrown money at petrochemical solutions, they haven’t been as supportive of natural and bio-based approaches.
There are however some very good centres of research that are being set up, such as at the University of Suffolk. Tom has also been in discussion with Cardiff University about doing some testing on further hempcrete houses that are being built in Wales.
“We know that they work, but it’s no good having the anecdotal information that we know that they work really well, and even better than synthetic materials. We need to have the hard facts, we need to have the data. And we also need to have more standards.”
Research in the UK and around the world shows that issues around mould are another big challenge that needs to be faced, even for properties that have been renovated. But there are now many in the medical community that are recognising the environmental causes of health problems, such as VOCs, formaldehyde etc. Tom sees natural materials as being the solution to get out of these problems, and this is likely to be one of the main directions of his work in the coming years.
Dr Judith Thornton of Aberystwyth University explores how plant-based materials are being used in the building industry, and why they are so important for our future.
Interview with Judith Thornton
Judith works within the Department of Biological, Environmental and Rural Sciences at Aberystwyth University. She specialises in projects at the interface of plant science and material function, with her main interest being the use of plants as building materials.
It’s about more than just building with straw or hempcrete
Judith says that, historically, because of the finely honed skills required for each approach, there has been a tendency for the natural building industry to divide off into those that build with straw, and those that build with hempcrete. There are of course many other plant types that can be used, depending on the design criteria.
She explains that we shouldn’t assume that we could build the whole project out of plants either, and nor should we assume that only one plant type will be suitable for each of the different building elements.
Judith uses walls as an example, where because they provide the dual functions of structure and insulation, it might make sense to separate those elements out and use different materials. She says that otherwise, wherever you’re trying to get a particular product to perform multiple functions, you may well end up with significant compromises.
Do your research
Even within strawbale building there are different types of straw that can be used, but Judith says people rarely demand a particular variety, and generally just accept what they’re given.
“I have yet to meet a strawbale builder who knew what wheat variety was in their building!”
Historically the tendency is to use wheat straw, within which there are also a number of varieties, but sometimes barley straw is used. Barley straw however is far more prone to rotting than wheat straw, which Judith says should be a bit of a red flag when thinking about building with it.
In Wales they have tested out building with miscanthus straw, which is a grass that can grow to three metres high, so is much tougher than wheat or barley, and presumably should be more resistant to breaking down.
Judith says that there tends to be an assumption that strawbale buildings are inherently low energy, but that’s not necessarily the case. If they’re not built properly they can be leaky and rot, not very airtight and have high energy bills in the same way that any other building can.
There is a lack of aspirational standards
“We’ve got a regulatory system where we’ve got a fairly ineffectual stick and absolutely no carrot. So, ‘this will comply with building regs’, and people will say that as if that’s a good thing. Well, complying with building regs is as bad as you’re allowed to be before you get prosecuted. That isn’t an aspiration, is it?”
Judith believes that there is a lack of incentive to build to the Passivhaus standard using low impact materials. She sees it is a combination of lacking aspirational standards and not valuing building enough as a trade, when it’s actually a very skilled profession and a challenging undertaking to build to Passivhaus standards.
One of the key challenges with Passivhaus is getting the airtightness, and particularly concentrating on the junctions between different materials. It can be as problematic for man-made materials as it is with plant-based materials though. Particular care needs to be taken when designing details at junctions between timber and straw for example, where you might get some shrinkage in the plaster when it’s butted up against a timber frame.
There would be no sense in trying to build an entirely plant-based building
Judith thinks it would be ludicrous to even try. Using airtightness tapes as an example, she explains it as the law of diminishing returns: where a small amount of a very high tech materials provides a massive benefit. She says there is no point in obsessing about whether your strawbales are tied with polypropylene string or whether your airtightness membrane has got formaldehyde glue in it.
“Partly because it makes almost no difference to the total carbon in the building and partly because it’s based on this completely false premise that natural things are safe and manmade things are dangerous. That simply isn’t true. But it’s a very commonly held environmental world view.
“We do this weird moral balancing in the UK where we say, ‘I’ll fly abroad on holiday, but I did do my plastic recycling’. The whole plastic debate for me is seeking to shift blame to manufacturers as an alternative to examining our own behaviours.
“It’s not rocket science. As individuals, we need to eat virtually no meat, we need to stop flying on holiday, and we need to insulate our houses.”
Establish what the building industry needs
Judith thinks that academics can have a tendency to come up with solutions for problems that don’t necessarily exist. So part of her role is having conversations with the building industry and the plant scientists to work out the areas that need new materials, and how the plant science community can contribute.
One example is of insulating solid wall houses in Wales and doing that with vapour permeable materials. She says that hemp lime or another material mixed with lime is an excellent way of achieving internal wall insulation whilst minimising risks of interstitial condensation. It then becomes a question of analysing what it is that the plant material is doing in that mixture, seeing whether other plant materials are available, and then carrying out testing.
Prevent biodegradable building materials from biodegrading!
There are significant differences between various plant materials in how easily they biodegrade, and this will impact on the longevity of a building. The key thing is to stop moisture from getting in.
Plants contain variable amounts of silicon and lignin in their cell walls which are protective against being broken down by microorganisms. Even different wheat straw varieties will contain different levels of lignin, which would impact on how quickly an individual piece of straw would rot if it were exposed to moisture.
So one of the initial decisions to make when planning your build is as to how you plan to deal with moisture, and whether for example you have a vapour-permeable construction where moisture can diffuse into and out of the wall, or whether it will be a completely sealed envelope that relies on mechanical or window opening systems for moisture management.
We will need to move to a plant-based economy
Before fossil fuels we had a plant-based economy, and going forward this is something that we will need to revert to once again.
Judith is involved in the university’s BEACON project, which looks at plants as products and how biorefining can help us move to a natural feedstock-based economy.
“Everything we use on a day-to-day basis, be it building materials or plastics or everyday items, is going to need to be made out of plants and it’s a question of how we best do that.”
Online Learning Resources
Check out these sites for online resources, including webinars and training:
Olga Turner Baker describes the WELL Building Standard and explains how the principles can be applied to improve health and well-being on individual projects.
Interview with Olga Turner Baker
Olga is a chartered surveyor by training. She first came across the WELL Building Standard back in 2016, and was surprised to find it wasn’t being adopted more widely in the UK. She quickly became passionate about it and started her own business, Ekkist, to specialise in design-led buildings, with a specific focus on health and well-being within.
Ori House
The WELL Building Standard is based on medical research
Launching in the United States in 2014, the WELL Building Standard took all the medical research that had taken place around the world that looked at how buildings impact our health, collated it over a seven year period and turned it into a building code.
Olga explains it as being a review of all the best practice and best guidance, of all the different components of building design. It covers the best guidance on air quality, water filtration, the safe use of building materials, and even through to management of buildings and how to operate them. It also touches on things like mental health and sense of community.
While there are criteria that must be met in order to achieve the minimum certification, there are also optimisations which are points that can be earned to get to a higher level.
Olga describes it as a very technical standard, where you submit documentation and are also tested in practice through performance verification testing. It is a robust procedure which assesses the building in use as well as in design.
There are ten core areas of buildings that the standard covers:
Air
This looks at air filtration and ventilation, keeping the worst of the chemicals and particulate matter and dust out of the buildings, so as not to exacerbate things like allergens or asthma.
Water
In much the same way as air filtration, this is to keep out anything that could be harmful, such as coliforms, public water additives, agricultural contaminants, and by-products of disinfectants. It’s about ensuring that the water has been filtered to a high quality, which can be through a carbon filtration system or reverse osmosis.
Nourishment
Probably more relevant to buildings that have an operator providing food on site, but also adaptable to our own homes, this looks at the kind of food that is provided within a building. It considers portion sizes, allergen labelling, and reduction of added and refined sugars and any kinds of additives. It encourages healthy food messaging by promoting ethical sourcing of products and eating as much fruit and vegetables as possible.
Light
Ensuring we have the right light in buildings helps keep the circadian rhythm and body clock functioning as well as possible. The standard has guidance on sufficient distances from windows, making sure rooms aren’t too deep for the windows provided, and that the right colour quality is being used in relation to the time of day or night.
Movement
This thinks about how we encourage activity in the building to improve health. It can be about connection with the outdoors to make it easy for children to play, or in larger buildings it may be about ways of encouraging staircase use rather than lifts.
Outside of the WELL Standard, but another idea that Olga suggests, is making outdoor space that is usable throughout the seasons, which will naturally encourage more outdoor activity for longer periods of the year.
Thermal comfort
Keeping buildings within comfortable thermal parameters is important for not aggravating conditions like asthma, eczema and stress, and making sure that our skin, eyes and organs function properly. Achieving this might be through shading and natural ventilation or mechanical cooling and ventilation systems.
Sound
Although not a mandatory part of the WELL Standard, acoustics make up an optimisation which far exceed UK building regulations.
It looks at both transference of noise between rooms and also transference within a room. Olga says there are plenty of products on the market which can help absorb noise, and materials she particularly likes using for this are cork and clay plaster.
Materials
Firstly this looks to avoid materials that we know to be toxic, such as asbestos, mercury, lead and PCBs. In the optimisations of the standard it also considers VOCs and how they can be released from furniture, varnishes, paints and glues. When you’re designing a home you should be trying to reduce these levels by looking at natural sealants and products like sheep’s wool as a furnishing fabric and natural oils.
As well as reading the specifications on the products, Olga suggests looking for external accreditation that any product you are using has been tested for a health component. Examples of these include Cradle to Cradle and Oeko-Tex.
Mind
This looks at how buildings impact our mental health, and what can be done to encourage better mental health through building design.
Much of this can be down to access to nature, whether that be views across to green spaces or incorporating greenery in and around your rooms.
Ori House
And even using wood and other natural materials has been found to have calming effects.
Community
The WELL Standard looks at access to community services, community programmes, and how you’re incorporating the wider community as part of your building and initiative.
Olga also recommends looking at the new NHS Social Prescribing Guidelines, which emphasise how our personal health can really gain from spending time with others, whether that be in group activities, gardening, etc.
Innovation
Olga describes innovation as being the most fun part of the WELL Standard. It is where you can be awarded points for coming up with new ideas that help increase health and wellbeing within buildings, that aren’t already covered by the standard. This could be anything like different lighting or having pets on site, as long as there is medical research to support the benefits.
WELL Standard principles can be applied to individual projects
While it is not possible to certify a single building, (there must be a minimum of five units and they have to have a common structural element) the principles and good design practice can be applied to individual projects.
While some designers might be doing these things intuitively anyway as good design practice, for others the standard can just push them a bit further and support them with the scientific research.
Ori House applies the principles
Ekkist have worked on a conceptual standalone dwelling, Ori House, where they have applied the principles and taken on the parts that really resonate to homeowners, such as the daylight, air quality, water filtration, and using space better for social interaction but also to encourage privacy within the home.
“We’ve tried to really think about that and create our own version of what it means to be a community but on an individual building level.”
Ekkist are currently looking for sites to build this on, and are also working on an urban version, which Olga sees as being important as cities become ever more urbanised.
“We want the quality and the health benefits of a rural home delivered in an urban environment. That’s our next big goal.”
