Contact →

Tag: insulation

  • HPH397: Sheep’s wool insulation and other natural fibre options – with Mark Lynn

    HPH397: Sheep’s wool insulation and other natural fibre options – with Mark Lynn

    Mark Lynn from Eden Renewable Innovations explains how sheep’s wool insulation is made, outlines the pros and cons, and suggests how it is best specified and installed. He also shares some common traits of natural fibre insulation as a category.

    Interview with Mark Lynn

    In this episode Ben Adam‑Smith sits down with Mark Lynn, Managing Director of Eden Renewable Innovations and Chair of the Alliance for Sustainable Building Products (ASBP). Together they unpack what natural‑fibre insulation really means, why sheep’s wool insulation is gaining traction, and what homeowners and builders need to keep in mind when specifying and installing products such as Thermafleece.

    Natural fibre insulation is any building insulation made from renewable plant or animal fibres

    Mark defines natural‑fibre insulation as any product whose primary component comes from a biological source – sheep’s wool, wood fibre, hemp, jute, cotton, flax and cellulose are just some examples. These materials can be used alone or blended, and they are often processed into batts, rolls, rigid boards, or loose‑fill. Because the raw element is renewable, the embodied carbon of the product is typically far lower than that of conventional mineral or synthetic insulation.

    “Natural fibre insulation is any building insulation that’s made from or using natural fibres.”

    The variety of fibres gives designers flexibility: wood fibre offers rigidity, hemp provides high tensile strength, while wool excels at moisture regulation. Understanding the source material helps you match the product to the building’s performance goals.

    Moisture‑buffering is a unique strength of natural fibres

    At the molecular level, natural fibres carry electrical charges that attract water molecules. Rather than allowing water to pool as a liquid, the fibres hold it in a solid‑state “bound” condition. This limits the risk of mould and rot, because the water cannot act as a universal solvent that accelerates decay.

    Sheep’s wool, composed of the protein keratin, is especially adept at this exchange, absorbing humidity when the indoor air is damp and releasing it when conditions dry out. The result is a more stable indoor environment, particularly in climates where indoor humidity fluctuates dramatically.

    “When the water molecules adhere to the natural fibre the way they do, they can’t behave like a liquid.”

    Breathability is not a substitute for ventilation

    Mark cautions that a breathable fabric does not eliminate the need for a proper ventilation strategy. Inside our homes we generate moisture through our activities (showering, cooking, doing laundry, etc.) so there needs to be a constant exchange of stale air being replaced with fresh air. In Passivhaus homes, for example, mechanical ventilation with heat recovery (MVHR) fulfils this role. The insulation’s ability to buffer humidity is therefore an additional benefit rather than an excuse to forget about ventilation.

    Good design requires adequate ventilation, sufficient vapour openness (the ability of water vapour to pass through the material), and the inherent moisture‑buffering capacity of the fibre. When these work together, the insulation remains effective without becoming saturated.

    Condensation risks can be modelled

    Tools such as WUFI can help model moisture, taking into account climate data, wall build-ups, and internal conditions. This will then identify potential condensation risks and allow them to be addressed at the design stage. Ignoring this step can lead to interstitial condensation and the knock-on effects of mould and damp, which in severe cases could even cause structural damage.

    Three main forms of natural‑fibre insulation: flexible, rigid, and loose‑fill

    1. Flexible insulation – often supplied in slabs, batts or rolls that can be cut to size.
    2. Rigid wood‑fibre boards – medium‑density panels that can be fixed to walls or roofs, offering structural support.
    3. Loose‑fill – shredded fibres (typically recycled newspaper or fine wood) blown into cavities, ideal for irregular spaces.

    Sheep’s wool is available both as flexible batts and as rolls, giving installers the convenience of a rockwool‑style product while retaining the natural advantages of wool.

    Sheep’s wool insulation is easy to install in a loft

    We should be taking advantage of all natural fibre insulations

    When asked about how we choose a natural fibre insulation, Mark suggests that it’s actually better to support the whole category. All natural fibre insulations will have their strengths. For example, when insulating a loft a roll of sheep’s wool may be the simplest and quickest to install.

    “We’ve got to use the right type of the right resource in the right way, and that really involves a whole mix of materials.”

    The ASBP’s Natural Fibre Insulation Group publishes a comparative guide that helps architects weigh factors such as thermal performance, acoustic qualities, fire resistance, and cost. Using that data ensures the selected material aligns with the building’s functional and regulatory needs.

    The market for natural‑fibre insulation is growing

    Historically, natural fibres accounted for roughly 1 % of the UK insulation market, compared with 10–15 % in France and Germany. Since the pandemic, consumer research into health‑focused homes has accelerated adoption, and manufacturers report strong year‑on‑year growth.

    Mark predicts that reaching the 10–15 % threshold in the UK would make natural fibres a credible mainstream option, offering homeowners greater choice without sacrificing performance.

    “These aren’t quirky eco products, they are part of the insulation mix.”

    Shearing a sheep for its wool

    Manufacturing sheep’s wool insulation

    Sheep’s wool delivers acoustic performance comparable to high‑grade rockwool

    Thermafleece UltraWool, a flagship wool product, achieves the same sound‑absorption ratings as a 45 kg/m³ rockwool product, despite being only 32 kg/m³. The lower density reduces dead‑load on the structure while still dampening noise, making it a compelling option for residential lofts and office partitions where acoustic comfort is a priority.

    Fire safety is addressed through mineral fire retardants, not by claiming non‑combustibility

    All natural‑fibre products, including wool, incorporate a mineral fire retardant that encourages charring rather than rapid flame spread. While they are not classified as “non‑combustible,” they meet Part B of the Building Regulations for the intended applications.

    For projects that require a non‑combustible rating—such as certain high‑rise or public‑access buildings—additional layers or alternative materials may still be necessary.

    Insulating a barn with sheep’s wool insulation

    Cost is competitive when viewed against performance and lifespan

    Mark notes that comparing wool to a cheap fiberglass roll can be misleading. When matched against high‑performance mineral products, the price differential narrows, especially when accounting for its long life (60 + years) and the reduced need for replacement.

    A typical loft installation with Thermafleece can be completed for under £1,000, and the energy savings often recoup the investment within five years.

    A thin layer of insulation can make a big impact

    When dealing with existing buildings, for example a period property with a solid wall, a thin layer of internal insulation can make a big impact to comfort and keep costs down. It must however be a continuous layer, eliminate thermal bridges and be installed well. One advantage of this thin layer is that you’re far less likely to have moisture build-up in the fabric, but you’ll feel a noticeable benefit to the comfort of the property.

    Environmental benefits extend beyond the insulation itself

    Sheep’s wool used in insulation is often sourced from the coarse, dark fleece that has limited textile applications, turning an agricultural waste stream into a high‑value building product. The polyester binder incorporated into the rolls is made from recycled plastic bottles, further closing the material loop.

    By sequestering carbon in the keratin fibres and reducing the demand for petrochemical‑based insulation, wool contributes to lower embodied emissions and supports rural economies.

    “We’re buying a reasonable proportion of the UK wool clip… adding value to the rural economy.”

    Find out more

    Other resources mentioned

    What is a healthy building product?

    Should you specify uPVC windows?

    Introducing the circular economy to housing

    What is the problem with plastic?

    How are building regulations made?

    How natureplus helps you identify sustainable building products

    What is wood fibre insulation?

    How easy is it to insure a natural building?

    Transcript

    Download a transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Follow Ben Adam-Smith on LinkedIn

    Follow Ben Adam-Smith on Bluesky

  • HPH389: Air-to-air mini split heat pumps – with Es Tresidder

    HPH389: Air-to-air mini split heat pumps – with Es Tresidder

    Es Tresidder from Highland Passive explains what an air-to-air mini split heat pump is, why he believes it’s a good choice for heating a high performance home and the various pros and cons of going down this route. He also reflects on one of the toughest stages of his retrofit when they took the roof off the existing dwelling and then faced torrential rain.

    Interview with Es Tresidder

    Es Tresidder is a certified Passivhaus Designer with over a decade of experience in low energy buildings. His consultancy Highland Passive helps self-builders and retrofitters create better homes, that are healthy, comfortable and energy efficient. He’s also been working on various projects for John Gilbert Architects over the years, and he’s a regular at House Planning Help as part of our ‘ask the expert‘ team in The Hub.

    Es has been on the podcast before, explaining how he upskilled in DIY during his retrofit project. In this session he’s reflecting on the whole process, including a key challenge he faced with water damage, and he’s going to go into detail about how he heats his home with an air-to-air mini split heat pump.

    Es is a regular in The Hub where he helps answer questions on building physics and retrofit

    Vehicle-to-load allows you to use an electric car’s battery to power external devices

    This podcast was recorded during a power cut and was only possible because Es has an electric car capable of vehicle-to-load, which means that you can plug an adapter in to where you normally plug it in to charge, and then plug a three pin, normal domestic plug into that, and run that into your house. He explains that you can’t power your whole house, but you can take three kilowatts from it, which he was using with three or four extension cables strewn around the house, to power the fridge freezer, the dishwasher, the Wi-Fi, to charge computers and even to make a loaf of bread overnight!

    “…logically, you know that electricity is very, very useful in life, but life just becomes much harder as soon as you don’t have electricity.”

    When Es put the services into the house, he created a service void, which is effectively a pipe that goes through the external wall with an airtight membrane on one side and a windtight membrane on the other. This means he can add new cables into the house and make them airtight easily. He did this when adding solar PV to the roof and now he’s done it again, putting in a permanent extension cable that can connect to the car, ready for the next power cut.

    Home battery systems with ‘island mode’ help you operate independently from the grid during a power cut

    Es explains that domestic inverters shut down when the grid fails, preventing the house from drawing power from solar PV panels during an outage. However, if you have a home battery system you can pay extra so that you can island from the electricity grid, which would happen automatically during a power cut. However, domestic batteries are only around seven to 12 kilowatt hours, so if it was January or February, with little solar power generation, you’d quite quickly go through your battery’s power, even in a Passivhaus. A car battery is much bigger, around 77 kilowatt hours, which would last several days during mid-winter, running heating as well as everything else. Another advantage is that if the power cut lasted much longer, he could just drive into town to a public rapid charger and top the car back up.

    Getting the MVHR back on was a priority because it immediately improves the health and comfort of the home

    Es says the MVHR has a really small energy requirement and is beneficial in lots of ways, so it was the first thing they plugged in. Until that point they had been keeping windows open for ventilation and, with an outdoor temperature of 12-13 degrees, the temperature inside had dropped down to around 17 degrees.

    The existing dwelling before any alterations

    The completed project

    Photography by Alex Trowski, commissioned for a case study in Passive House Plus Issue 50

    The retrofit, extension and remodel has made the whole house work better as a home

    Es’s house was a 1975 timber-frame build of one and a half storeys, where the first floor rooms felt quite pokey. So the strategy was to take the whole first floor off and rebuild it as a one and three-quarter storey house. This may not sound like a big increase, but Es says it gave a lot of extra floor space on the top floor, with enough for an extra bedroom, and an increase in size for the other bedrooms. The floor plan just worked much better.

    The upper floor is a new build Passivhaus, with an I joist timber frame sitting on top of the existing structure, which was quite complicated to do. Downstairs is a retrofit of a 100mm timber frame house, where the plasterboard was taken off and insulation put between the studs. He then added another 40 mm of wood fibre insulation board, an airtightness membrane, and then outside of that is white rendered blockwork. There’s a cavity between the two. As a Passivhaus Designer, Es did all the energy side of things and a lot of the retrofit work himself. The new build was carried out by a local contractor.

    The project involved removing the pitched roof and extending upwards

    Keeping a flat roof dry is incredibly difficult

    This project required the first floor and roof to be removed, which is slightly unusual. When they were looking at the options, one way to keep everything dry was to put up a massive tent over the whole structure, but this would set them back £30,000. The builders, however, were confident that they could keep the water out because they had done this many times before. There was also the fact they would be doing this in May which is statistically the driest time of the year in Fort William. Unfortunately the weather did not play ball and it was an unusually wet month. Es also points out that although the builders take off lots of roofs they probably don’t remove the whole structure leaving effectively a flat roof to keep dry.

    So it just became impossible to protect the structure from the torrential rain. Es had already insulated the ground floor and achieved good airtightness but the rain soaked the floorboards and insulation, forcing him to strip them out and replace everything.

    “You don’t want to install any insulation until the building is watertight.”

    A lot of insulation got waterlogged and had to be replaced

    Sequencing the work differently would have avoided damaging the insulation

    If doing the project again Es would not necessarily pay for the giant waterproof tent but he would sequence things differently. The work downstairs had been done first to ensure structural stability for the new first floor and roof. However once rain had compromised the work, they had to go ahead without the extra racking boards on the walls anyway or the racking strength from the floor. He would therefore consult a structural engineer to look at any structural elements that could be done without involving the insulation.

    The unit inside the house

    An air‑to‑air mini split heat pump is a cost effective way to heat a low energy home

    For Es, a heat pump is an obvious choice over direct electric resistance heating. However, instead of a conventional air‑to‑water heat pump system, Es chose an air‑to‑air mini‑split system. He explains that this is like an air conditioner, which usually pumps heat from inside to outside a building, but can also be used to pump heat from outside to inside a building. They have a similar efficiency to an air-to-water heat pump, but are much cheaper to install, because there’s no need for radiators or a wet system. The mini split has an outdoor unit and an indoor unit, with refrigerant lines between the two. The unit and installation cost was around £1,500 compared to £12 000 for the air‑to‑water system. Es is clear that this system is great for a Passivhaus but wouldn’t work for a normal new build house as it only delivers heat into one room and relies on heat spreading to other rooms.

    The unit outside the house

    Reversible operation provides useful cooling in heatwaves

    Mini‑splits can run in reverse to deliver modest cooling, which has proved handy for Es during a heatwave which coincided with the midge season (when they don’t really want to open any windows) and a large group of friends staying over and thus raising the indoor temperature.

    Sizing the mini split above peak load ensures comfort in cold snaps

    The house’s peak heating demand is around 1.3 kW and by selecting a 2.7 kW mini‑split Es has provided a comfortable margin, which allows the system to cope with occasional freezing cold days without needing supplementary electric heaters. In cold weather he will run the system overnight when electricity is cheaper, so increasing the temperature in the main parts of the house, whilst the bedrooms stay cooler. Once the doors are open the heat can spread through the house. He admits that having his office in his bedroom means occasionally it can be cooler than he would like and so a small electric heater would probably be a good addition.

    Photography by Alex Trowski, commissioned for a case study in Passive House Plus Issue 50

    Locate an air-to-air mini split system in a large open area

    Es explains that the mini split system needs to be in a space big enough to deliver a lot of heat into it, before warming that space to above the set point temperature. A small room would reach that temperature quickly then the system would shut off and so not provide enough heat for the rest of the house. The indoor fan also produces a low hum comparable to a refrigerator, louder than the house’s MVHR, so you need to place it where the noise won’t matter too much. Es stresses that whilst the MVHR supplies fresh air, and recovers heat it only moves a small amount of warm air between rooms. Keeping interior doors open lets the warm air from the mini‑split circulate more effectively.

    Grants favour air-to-water systems, but air-to-air systems may still be cheaper

    Even though Scottish renewable‑heat grants are available for air‑to‑water heat pumps and not for air‑to‑air units, Es feels the air‑to‑air solution may still be cheaper. The grant system also involves a lot of paperwork and restricts you to using MCS certified contractors, who are not necessarily the best. For a Passivhaus going down the air-to-air route also means you keep things simple.

    A standalone hot water pump works alongside the air-to-air system

    Whilst air-to-water heat pumps can also be used to supply hot water, an air-to-air mini split system is just warming the air in the house. So Es has installed a heat pump water heater, which is a 200 litre insulated hot water tank with a small heat pump on top. They are normally ducted to the outside to bring fresh air into the heat pump, the heat pump takes some heat out of that outdoor air, and then it ducts the exhaust air back out. Es has set his up to take heat from the house, which gives some free cooling in the summer and a much faster reheat time in the winter. It’s also easier from an airtightness point of view as it is not ducted to the outside at all. In the winter, the water heat pump is slightly cooling the house, so the mini split has to work a bit harder, but overall, it is still very efficient.  

    Living in the house has been amazing

    The house before Es started had quite serious mould and damp problems. They were always a bit chilly in winter and couldn’t dry things because there was no reliable ventilation, and the house wasn’t warm enough. Now things are completely different.

    “It’s hard to remember how it was before, because it’s just so nice now.”

    The house is warm and comfortable all the time in every room. Es believes it’s almost more impressive in hot weather than it is in cold weather, when you expect it to be warm. Es says that the first summer they moved in, they had two separate weeks of more than 28 degrees as peak temperatures in the afternoon. And in those conditions, the house was at 23 degrees, and it felt like walking into an air-conditioned space. It has really improved the quality of life. The air is clean and just walking outside the house, Es immediately notices if the neighbours oil boiler is running or there’s a coal or wood fire on locally.  He thinks his sense of smell has improved, because he’s used to clean air and the house smells fresh all the time. The best thing isn’t the bills, but it’s the most quantifiable thing. He’s reduced his heating bill by at least 80% while also massively increasing the average temperature of the house.

    “After one full year of monitoring we have spent £175 on heating and hot water for a family of five, which is remarkable.”

    Find out more

    Highland Passive

    Heat Geek

    OpenEnergyMonitor

    Transcript

    Download a transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Follow Ben Adam-Smith on LinkedIn

    Follow Ben Adam-Smith on Bluesky

  • HPH386: The potential of mycelium-based composites – with Joshua English

    HPH386: The potential of mycelium-based composites – with Joshua English

    Joshua English, co-founder of Okom wrks labs shares his journey into the creation of a mycelium-based composite material, which has structural and load-bearing properties.

    Interview with Joshua English

    Joshua English, co-founder of Okom wrks labs describes himself as a jack of all trades with a lifelong obsession with fungi. Although he did an arts degree, he realised he loved working with numbers and so spent his early professional life in database programming. After 18 years doing data analysis and data visualisations for healthcare he started to miss the physical world. He then took a degree in Interior Architecture and Design, with an emphasis on industrial design which led to a hyper focus on materiality. A long-time carpenter, with a love of metal and concrete and the knowledge that those materials were not great for the environment, he wanted to try to find the most sustainable way to build things. When a friend introduced him to mycelium-based composites about six years ago, he took a deep dive into the subject.

    Could he make a chair using mycelium-based composites that people could sit on?

    In his research he came across pictures of chairs made from mycelium-based composites, but nobody was sitting on them. Could he be the first designer to make a chair that a human could sit upon? He spent six months gathering information on the technology with a plan to spend two years researching how to make mycelium-based composites stronger. He ended up finding a solution much quicker through a random application of materials left over from his first set of experiments. He then had to reverse engineer from this “mistake” to work out what had happened. It took a few years to patent this process and they are now looking to patent the material itself.

    Mycelium are fungi and not to be confused with plants

    Mycelium is fungi, which is in its own kingdom and not to be confused with the plant kingdom. Joshua explains that where animals engulf their food and plants photosynthesize, fungi absorb their food, so their whole lifestyle is centred around surface area. We think of mushrooms as fungi, but they are just the fruiting body, the mycelium is by far the vast majority of the organism. He compares it to an ant colony, where the individual ants are like the hyphal strands of the mycelium. A mycelium will have billions of hyphae that branch out to explore their environment. They provide a large surface area and exude enzymes to absorb their preferred food source. To do this the hyphal strands need to be incredibly strong, durable, and multi-use as well. Joshua is exploiting the capability of the fungus to create an adhesive to use as part of the matrix of a composite material. Not all fungi have the capabilities to create strong mycelium-based composites, and so far, mycologists have found that fungi that grow on trees are particularly well suited for this.

    This technology is still in its infancy

    The technology goes back to the early 2000s, but it has grown and developed in the last 25 years. Philip Ross, an art major at Stanford and a lifelong mycophile started to develop processes to make things out of mycelial colonies about 20 years ago. He then used mycelium blocks to create striking artworks and published his findings, which people started to notice. Some engineering students in New York, then developed a business model to use this technology to make a foam packaging replacement. They tried to commercialise it about 13-15 years ago. When researchers started to look at the key qualities of the mycelium-based materials they were impressed with its fire resistance and sound attenuation, but it was not so good structurally or when it came to water absorption. This led to them being relegated to insulating panels or decorative wall sound mitigation panels.

    “And then, you have a guy like me who makes a mistake in the lab and then finds this way to make what seemed to me to be structurally sound materials.”

    Turning it into a business is a huge challenge

    Joshua believes that a 5 -10 year time frame is needed to go from the research phase to a commercial product. In his experience Venture Capital investors want more of a 2 year turnaround, so there is a mismatch here that needs to be overcome. Because it’s such a new technology there is a lot of siloing happening along with a push to early commercialisation. There is also a big rush to patent the materials, because you don’t want to be overtaken, but this has all led to a stifling of the technology and people making wild claims. Joshua is clear that any claims need to be backed up with data and currently there are no standards for how we measure and create these things. Joshua thinks that for this technology to move forward governments need to subsidise it and universities need to continue the research. It needs targeted attention and standardisation of methods, but none of this is going to happen without funding. Joshua believes the capabilities for mycelium composites are endless, as endless as the kingdom of fungi.

    The mycelium-based composites are grown in the lab

    Joshua explains that you need at least a food grade level of facility to grow the fungal starter culture, very different to a standard sawmill making SIPs. But one of the amazing things about this technology is you can start from a single fungal spore and grow enough material in about 90 days for several houses. During the process, the spore starts in a petri dish, and you grow it, adding a bit of material at a time. You can increase the amount of material you add as it builds up, whilst making sure the fungus isn’t getting too old, because its life cycle can be rapid. Joshua grows the material in the open air and doesn’t use rigid moulds. A remarkable part of the process is that it takes five days to grow, whether it’s one metre or ten metres, it’s the same amount of time. During that time, it fully colonises the substrate and forms a fungal skin around the outside of the material, which is tough and durable. At the end of the process, you dry it, to kill the fungus, as you don’t want the fungus to continue to digest the material. It is the drying process that gives it the rigidity and strength.

    The Hy-Fi tower

    Experimental projects demonstrate potential for the future

    Joshua completed a non-structural project in New York City two years ago using their mycelium-based composites. The second half of that project was to include the manufacturing of chairs, but difficulties in finding the right facilities to dry the material brought things to a halt. The Hy-Fi tower at PS1 in New York City is a well known example of using mycelium bricks in a large structure. However, the tower was built of timber and the bricks are just infill. A man in Ohio has used edible mushroom mycelium blocks, compressed at a 20:1 ratio to make strong materials. Joshua is trying to develop a different process, which tests how far the fungus can go itself, so not using any industrial compression to bring strength. He is also currently limited in the size he can make, at 3m long by 300mm wide.

    Okom wrks labs could also look at creating a two by four wood replacement product but at this stage it would not be as strong as wood. However, they are finding that if they grow several parts together, at the same time and cross layer them, they can build an incredibly strong 2 feet by 2 feet SIP wall section. In their trial seven parts were all adhered together by the mycelium itself. There was no glue involved and although they didn’t get to do a compression test it did seem like there was a synergistic effect by growing them together in this way. There are more collaborations brewing and the potential for space technologies for drying that would make it possible for them to restart building SIP wall sections.

    Working at full scale they could compete with standard SIP wall panels

    Very early on Chris Magwood suggested concentrating on structural insulated panels (SIPs) and Joshua believes that if they could work at full scale, they could produce mycelium-based composite SIPs at a competitive price. Over time, they could make that difference even greater.

    Mycelium-based composites are already being used outside construction

    Mogu in Italy has been creating decorative sound attenuating wall panels for a long time now, which has kept the material in the zeitgeist. There have been several attempts at creating businesses with foam packaging, but it’s been rather difficult to commercialise the products overall. Le Corbusier regarded chairs as small pieces of architecture and as Joshua is also infatuated with chair design, he thinks a fully mycelium-based composite chair could be the way to show people what is possible. It would show the industry that it can be done commercially, and consumers that you can put these things in your house. They’re not going to grow weird things off the sides, and they will have some heirloom quality to them!

    It is healthy for people with allergies to mushrooms

    In Joshua’s process the fungus is killed at a certain point and never reaches the fruiting body stage, which means spores are not produced. It’s usually the spores that people have sensitivities to, so it’s therefore completely healthy. The other issue is that most mycelium-based composites are incredibly hygroscopic, which means they will take up a lot of water. Other moulds or anything else, could start to colonise the material in a wet state, so you need to be able to stave off that moisture. This would be about protecting it from the elements, like you do with timber, so you would then have a system with longevity. Joshua admits its early days and hypothetical, but from his own research he thinks it is doable, and it is safe.

    He explains that whilst foam-like mycelium-based composites typically have a water uptake of 200 to 300%, their material is far more dense, with a water uptake of around 25 to 45%. That’s a big leap in the right direction with more improvements possible through improving the fungal skin or adding natural products like beeswax. His goal is to avoid any kind of petroleum based products, if possible, but has accepted that using an epoxy resin covering may be a good way to get things started.  

    Hemp is the Joshua’s preferred substrate for growing the mycelium

    Joshua is developing a composite material, which we might compare to the first earth bricks that included straw to add strength to the mud. He is using hemp as the substrate for the mycelium to grow on as it is a strong material and is “tasty” to the fungus they’re using. The fungus serves as an adhesive that binds everything together, so you’re using these two different materials to create something like a brick. He then adds in the textile reinforcement phase that provides even more strength and improves the compressive strength by orders of magnitude over the foam-like materials and other types of mycelium-based composites. That textile reinforcement phase is notoriously difficult as it needs to be clean enough to grow without it getting contaminated before the end of the grow process.

    We need to re-imagine how we use materials

    Even though Joshua’s data is showing increased strength in the material it is still only just over one megapascal in compressive strength. This is not great from an engineer’s perspective, so can we think differently about how we build? He is thinking about modular building rather than lots of concrete and brute strength. Instead use geometry and genius engineering to build lighter, stronger structures. Anything that makes steel lighter and stronger from a geometry standpoint, would also work with their material. There is also work to optimise the way that the fungus grows and possibly some genetic changes to the fungus that would enhance certain qualities. Machine learning can help with this process as there are so many variables to consider. People are now starting of pool resources, with Phil Ross, setting up a nonprofit, called Open Fung. This is to create baselines for researchers, so people are not starting from scratch each time and can hopefully go further and faster on the engineering side.

    The potential applications are as diverse as the kingdom of fungi

    Joshua believes that the potential applications for mycelium-based composites are as diverse as the kingdom of fungi, but the material needs to match the job it’s meant to do whether that’s in industrial design or architecture. It’s also important not to oversell the capabilities. Whilst patenting is important to gain investment, there is a need for more collaboration in the field, and that is Joshua’s request to the mycologists and engineers currently exploring these ideas.

    “I think the future is wide open as we are at the nascent stages of understanding how fungal mycelium-based composites come together.”

    Find out more

    Okom wrks labs

    Follow Joshua English on LinkedIn

    Transcript

    Download a transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Follow Ben Adam-Smith on LinkedIn

    Follow Ben Adam-Smith on Bluesky

  • HPH371: What is wood fibre insulation? – with Chris Brookman

    HPH371: What is wood fibre insulation? – with Chris Brookman

    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.  

    Check out our live training with Chris Brookman on the roles of insulation.

    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.

    Find out more

    Back to Earth

    The Alliance for Sustainable Building Products

    Transcript

    Download a transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Like our Facebook page

    Follow Ben Adam-Smith on Bluesky

  • HPH366: Could a home energy transformation pay for itself?

    HPH366: Could a home energy transformation pay for itself?

    Howard Johns, founder of One Zero, outlines their home energy transformation service which includes topping up insulation and adding solar PV, battery storage and a heat pump.

    Interview with Howard Johns

    Howard shares his extensive knowledge of renewable energy, and how he has moved from managing a large portfolio of solar and wind farms to enabling people to generate their own energy. Over the years it has become apparent to Howard that the real sticking point with the large scale projects is the National Grid, which is currently struggling to take new connections. His new company One Zero energy, is focusing on how we retrofit homes in an efficient and light way that can enable them to become part of a new, flexible, distributed grid.

    The UK grid is no longer fit for purpose

    Electricity companies began as regional entities, with one power station supplying each local area, which worked until there was a problem with that station or too much demand. With no back up in the system, some areas of supply would have to be shut down to enable other areas to keep going. Our current grid system was a national project to join all these power stations together with transmission lines so that it had more inherent flexibility. But essentially, it was built as a one-way system, with power being generated in a small number of locations and then flowing to a large number of supply locations.

    With the advent of renewables, particularly wind and solar, distributed generation emerged. So generation is happening in all sorts of locations and Howard explains how we are rewiring the grid backwards to allow this, which has caused a lot of issues. In fact, in many areas it is just not possible to connect any more large-scale renewable generation because the infrastructure cannot take it. If we can’t do that and need energy transformation now to tackle climate change we need to look at other options.

    The current energy system is extremely inefficient

    Howard explains that for every 100 units of gas used only 40 of those turn into useful units of electricity. During transmission to our homes another 10% is lost and then we might lose more through inefficient appliances. The usable energy you’re getting in your home from that primary energy is around 30%. So if you start to generate energy where you need it you can massively reduce the wastage.

    With heat pumps we can be getting 400% more energy out of it than we put in, compared to maybe 90% efficiency with a gas boiler. It is similar with transport, a standard fossil fuel car is about 30% efficient, whereas you can double or treble the efficiency for an electric vehicle. In other words the new electric based technologies that are emerging are the future.

    A resilient energy system has more back-up options

    Howard outlines how we already have at least five interconnectors into this country to build resilience in the system. A European wide grid allows excess energy, say from Denmark, to be supplied to other European countries.

    Behind the scenes at the National Grid (NESO) people are looking at live demand, and turning on things like peaker plants and gas plants, and using batteries in some cases to meet that demand.

    A resilient system must get past intermittency

    As the amount of renewable generation increases, there’s a new challenge – intermittency. So there will be a correlation between the weather conditions and how much is generated. For example, on a sunny day we might generate 20% of our power from solar, but there will be nothing at night. At times we will get really high levels of grid energy powered by the wind, but on a still day, we may get very little. This is one of the key features of the new system and it is causing problems.

    Better storage capacity will help solve the problem

    As the cost of energy continually changes if we have the access to battery storage then we can benefit. So it makes sense to use energy at key moments, when it’s abundant and cheap, and avoid using it at six o’clock in the evening when the demand is highest and it’s expensive.

    It’s always preferable to use energy as it’s being generated

    Howard tells us that it is preferable to use energy as it’s being generated because there will always be losses associated with storage. With batteries you lose around 10% of the energy you put in, just in charging and discharging. However if you haven’t got demand for that power, it’s still a sensible thing to do.

    Part of One Zero’s strategy is to install a solar PV array in combination with battery storage. This would mean that for eight months of the year you could be virtually self-sufficient for power. With a decent control system you can effectively run your battery as a micro power station profiting from arbitrage and engaging in the flexibility markets.

    Import and export to the grid when it makes financial sense

    With many big batteries being built across the UK there may be times when power is cheap or even free! So, in addition to your own generation, in these moments it may make financial sense to import from the grid to charge your home battery or discharge power back to the grid.

    Innovative companies, like Octopus and Ovo, already have flexible tariffs that will give you different power prices at different times of day.

    Howard thinks the next step would be managed services that take into account wholesale prices, which change every half an hour. Again these have periods where energy is very cheap or even negative, and other times when it’s expensive. With an agile tariff you could see prices change from -2p to 50p a kilowatt hour over a 24-hour period. Software is needed for this management, however, and this is a service that One Zero are working on.

    “Generating and storing power at your home is probably the most cost effective way of getting power right now. Not many people realise that.”

    Heat pumps will work without a deep retrofit

    Using heat pumps is another part of the One Zero energy transformation strategy. People may be under the impression that a deep retrofit – improving the thermal performance, and the health and comfort of the building – is required to make these systems work but that is not the case. So at One Zero they suggest a light touch retrofit, topping up insulation levels and doing the easy wins.

    Howard points out that putting a heat pump on a really leaky house is going to be inefficient, but heating it with a gas boiler is also inefficient, so on one level there’s no difference. At the same time, if you use a heat pump, you may also knock four or five tons off your CO2 emissions every year.

    However, it still makes sense to do as much as you can to reduce heat loss. When One Zero assess a property, they’ll make recommendations around deeper measures, which could be done first or incrementally over the following years to improve efficiency.

    Considering payback has been a big part of this approach

    One Zero are looking at measures that could start to pay back in 5 years rather than 40 years or more for deeper retrofits. Howard believes there are millions of homes that need to be improved in the next decade or two, so it’s important that this really appeals to people and offers a clear win. By starting with solar PV and a battery people can achieve a cash flow that they then might reinvest in the next steps. One Zero are also looking at finance packages so you don’t need all the capital upfront to get started on this home energy transformation.

    One Zero plan is for people not looking to do a deep retrofit

    Howard explains that One Zero is aiming to reach people that will not undertake a deep retrofit of their property, either for financial reasons or lack of engagement with this approach. Their approach is to provide a top up for cavity wall and loft insulation and then solar PV, a battery and a heat pump all for around £21,000. You could have a home energy transformation that would drop your bills by around 50-60% and your carbon emissions by 70%, all delivered within two weeks with minimum disruption. They think this is achievable for homes built after the 1930s, which already have some cavity wall insulation, double glazing and some loft insulation.

    What is a deep retrofit? Check out the Kinver story in The Hub.

    Every technology has an impact, but this should be weighed up against the alternative

    Howard has put a great deal of research into the One Zero home energy transformation package. He believes that if we reached 100% renewable generation our rates of extraction of raw materials from the earth would drop to about a 30th of current levels. The backdrop is that we live in a highly extractive society, where 40% of global shipping relates to fossil fuels.

    Everything we do has an impact, so with solar panels, there’s polysilicon production and issues around the supply chain, particularly with indentured slavery in some provinces of China, which can be hard to get around. This is also the case with many other products we are using. A solar panel can liberate the energy that went into making it within nine months of it being in use and the panels then have a 25-year warranty and possibly up to a 40-year lifespan. Most modern solar panels don’t contain any rare earths, they are just copper, an aluminium frame, silver for the conductors and glass. Effectively, polysilicon is a form of refined sand, and so all the parts are recyclable. There isn’t a huge recycling market yet, because most of the panels that have been installed are still in use.

    People are also concerned about the huge amount of lithium being produced for home and car batteries. Howard explains that there are two ways in which lithium is produced. One is from mining, generally in Australia, whilst in the rest of the world lithium production is from liquid deposits. These exist as brines under the surface of the earth that can be extracted through a bore hole. The lithium is then taken out and the remaining liquid is pumped back down. So there is an impact but it should be smaller than for mining. Also lithium is a recyclable material, which is abundant in the UK.

    Many manufacturers are now redesigning batteries so that they don’t contain cobalt, so as we move forward there should be fewer issues around rare minerals.

    Heat pumps are generally made from copper and steel, both of which are abundant in a recycled form across the world. There’s a refrigerant involved, with two possible types, one of which has a lot less global warming potential.

    All of these technologies will have a lower impact when compared to the extraction of fossil fuels and the resultant CO2 emissions from using them.

    A repowered house – taken off the gas network

    Your home can help you reduce your carbon footprint

    For a typical dwelling One Zero’s home energy transformation could save between 3-6 tons of carbon over the course of a year, which is equivalent to 20 or 30 flights to Spain. For Howard this is incredibly impactful.

    Your electric car battery could support your home energy use

    It’s still early days but trials in vehicle to grid energy transfer could support our home energy use. An electric car could have a 30-100 kilowatt battery in it, while your home battery may only be 10 kilowatts, so if you could plug your car into your home and use your car battery to support your home that would be valuable.

    It’s also a lot of lithium sitting around that could be used more effectively. Nissan is currently the only car manufacturer that allows this but that could change. The challenge is that most car manufacturers want their batteries used solely for powering their cars and consequently you will invalidate the warranty if it is used for other purposes.

    However, these batteries have huge potential to increase storage capacity and help with the intermittency challenge in power generation. And Howard suggests that even accessing 10% of these batteries could have a meaningful impact.

    One Zero has a community focus to support people on their renewable energy journey

    People can be cautious, so One Zero is working to give people the confidence to act and then supporting them to share their experience with others. Currently they are geographically focused, working in communities where they can sign up more than one house at a time, maybe 5-10 houses across two or three streets. So they are reaching out to people who may not have thought they could be part of this journey into renewables, to help them change the way they think about it.

    One Zero is operating in Sussex at the moment and has plans to launch in more areas over the course of the coming year. The next steps could be looking at managing a micro grid behind a distribution transformer that serves a street, so there would be enough generation and storage to provide the community with power for a large part of the year.  

    “It’s turning it from, that me and my castle thing, into us and our street.”

    Find out more

    Transcript

    Download a transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Like our Facebook page

    Follow Ben Adam-Smith on Bluesky

  • HPH365: Becoming a housing activist – with Cypren Edmunds

    HPH365: Becoming a housing activist – with Cypren Edmunds

    Cypren Edmunds, a housing activist and advocate for bio-based building materials, describes the challenges he has faced living in social housing in London, and the health benefits and energy efficiency that can be achieved through building with straw.

    Interview with Cypren Edmunds

    Cypren is the Chairperson of Strawbale Building UK and the President of the European Strawbuilding Association, and is working to increase the use of straw and other bio-based products within the construction industry.

    Cypren has first-hand experience of living in UK housing that is not fit for purpose and the affect this has on family life and the wider fabric of society. He believes we need much more education within the construction industry and society at large to enable us to build healthier and more energy-efficient homes.

    Activism begins with a burning desire to make a difference

    Cypren describes how living with his family in a property that had damp and condensation became distressing, and drove him to become a housing activist and ultimately to change his career. He started by re-igniting the Residents Association for his housing estate, but quickly realised that collectively they didn’t really have the knowledge of the built environment, planning and housing regulations to get to the core of the problems they were all facing. Cypren, a qualified carpenter, was working in fitness training at the time, but decided to change direction and see what he could do.

    Activism requires upskilling and plenty of time

    Cypren knocked on doors to find out just how bad the situation was for residents. In one of the worst cases, water was dripping from the light bulb above the resident’s head and as you walked through his flat, every single wall was dripping with condensation and mould. The resident had complained to both the Housing Association and Local Authority, but nothing had happened.

    A wall riddled with damp and mould

    The fabric of the buildings is concrete and steel (with fan heating) with no apparent strategy for dealing with ventilation, so moisture becomes trapped. The Housing Association didn’t have any solutions, apart from leaving windows open or putting in noisy dehumidifiers, neither of which worked well for residents.

    Keep communicating and stay engaged with all parties

    Rather than getting aggressive the Residents Association genuinely wanted to stay positive and work with the Housing Association and the Local Authority to identify solutions. As the Housing Association had already carried out surveys of the building, they too realised how bad the situation was and that it needed addressing. However they admitted they didn’t have the money for a full retrofit, so after much consultation tenants voted for regeneration.

    Cypren outlines the role of the Residents Association in explaining the wider picture to residents and wading through the multitude of facts and information provided by the authorities. Many people didn’t understand the bigger picture, only how things related to them, and this is a political problem that needs to be addressed.

    “We don’t have enough skilled professionals, at all levels, in the construction sector to undertake the kind of retrofit work necessary for these types of properties.”

    Council houses in North Kesteven

    Low carbon bio-based materials have many benefits

    Whilst straw was rejected as a material for the regeneration of Cypren’s housing estate it is being used widely across Europe in the construction of a variety of public and private buildings.

    As President for the European Straw Building Association and chair the Strawbale UK, Cypren is working to get the message across politically and digging into policy and regulations to increase use of bio-based materials in construction.

    A firestation in Colombey Les Belles, France

    Meliana day care centre in Valencia, Spain

    Countries like Lithuania and France are way ahead of the UK in recognising the value of straw and other bio-based materials. The French have entrenched this methodology into their regulations. For example policy RE 2020 is an environmental regulation that came into effect in 2022 with the goal of improving energy efficiency and reducing greenhouse gas emissions. Cypren points out that we just don’t have this in the UK, and whilst groups like ACAN are doing a great job of delivering that message we need much more.

    STBA and SPAB hold a joint conference

    We need more education around the use of straw

    Cypren is clear that in the UK we need a significant drive to enable people to understand the value of using straw and other bio-based materials within the construction industry and that this drive should come from Government. There is a lack of education within the construction industry itself and many myths around straw that make the public wary of its use.

    Get input from experienced natural builders

    As with any material or methodology it’s essential to understand how you work with bio-based materials and how it differs to other approaches so make sure you’re learning or engaging with experienced natural builders. The good news is that straw is not a difficult material with which to work, particularly if you’re already a plasterer or carpenter, etc. The skills necessary are just the same as you would need if you were going to build a timber framed house. And now with prefabricated straw panel systems it is even easier, with construction on site taking just a few weeks.

    Highly engineered straw panels at Old Holloway

    Cypren believes we need to be building more with straw panels and developing factories to produce them. This would be good for the economy and generate jobs. We’re told the construction sector is struggling, so let’s train young people to work with materials that are helping us to move forward in life. It’s up to the government to give the appropriate incentives to those large housing developers to incentivise them to build in that way. We should take inspiration from France. Cypren tells us of a conference last year, where the French were saying they’d just built over 10,000 homes with straw. He couldn’t say how many we have built in this country.

    Intelligent activism could help create better homes and communities

    Cypren feels that if we are not happy with the situation within our community, we need to work together to create change. For him it’s not about going on marches or rallies it’s about engaging with the authorities, commenting on consultations, and making sure your voice is heard. He believes we have a tendency in England to sit back and expect others to sort things out. Instead, he suggests we find like-minded individuals, share ideas, speak to experts to get the information needed and become active with our community.

    For us to have a healthier society, we need to be thinking of everyone. There is a knock-on effect for example for young people living in poor housing, who are ashamed to take friends home, with no youth centre to go to, and so they hang around outside and potentially become involved in anti-social behaviour. If homes are comfortable and inviting people will want to be there instead.

    Keep an open mind to bio-based materials

    Cypren’s overriding message is to keep an open mind to bio-based materials. He says there is massive potential to scale up and that it would enhance all of our lives.

    From all of the data and all of the reports Cypren has seen, people who live in straw buildings or own bio-based buildings tend to be happier and healthier.

    Querbeet Housing Project in Lüneburg, Germany

    Find out more

    Sustainable Traditional Buildings Alliance

    European Straw Building Association

    Straw Bale Building UK

    The Society for the Protection of Ancient Buildings

    Transcript

    Download a transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Like our Facebook page

    Follow Ben Adam-Smith on Bluesky

  • HPH354: How natureplus helps you identify sustainable building products – with Tilmann Kramolisch

    HPH354: How natureplus helps you identify sustainable building products – with Tilmann Kramolisch

    Tilmann Kramolisch from natureplus explains why their eco label was established, how materials and products are assessed, and what it means to use a natureplus certified product on your project.

    Interview with Tilmann Kramolisch

    Tilmann Kramolisch is the Managing Director at natureplus, a non profit eco label that aims to provide transparency and clarity to the consumer within the construction sector. The natureplus accreditation measures the impact of different building products on the environment and human health, to ensure that any product with a natureplus label is certified as healthy and sustainable. In this chat, Tilmann talks us through the natureplus accreditation process as well as highlighting some key differences to be aware of in other eco labels.

    Healthy building products don’t harm the natural world or human health

    The natureplus eco label certifies that building products are not harmful to the environment or human health. The World Health Organisation (WTO) has classified a condition called sick building syndrome, which refers to the negative impacts that a building can have on an occupant’s health. Leading causes of sick building syndrome are damp/mould issues, poor ventilation and toxic emissions from materials or the environment. Many natural building materials are proven to tackle these issues and by reducing the use of harmful chemicals/pollutants, the environmental and human health risks are significantly lower.

    Materials are not the same as building products

    Tilmann makes a key distinction between building materials and building products. Materials refer to a substance that can be made into many different things depending on how it is treated or used, whereas a building product refers to one of the outputs. Tilmann uses clay as an example of a building material, that can be used to make the building products of plaster or bricks. Natureplus measure the sustainability of building products on the market.

    The natureplus eco label takes a holistic approach

    Tilmann explains that the natureplus certification rests on three core pillars:

    • Health
    • Climate protection
    • Sustainable resourcing

    For a product to be classed as a healthy product and receive natureplus accreditation, it must consider all three of these in all aspects of its usage and existence.

    Asbestos is a good example of a product that would have failed the natureplus accreditation. It was originally considered a great material with many positive attributes. However, we now know how harmful it is to our health and when a building is deconstructed this material must be carefully removed and disposed of. This therefore negates the previous intention of saving resources as it cannot be reused. So if you begin with the three pillars approach when creating a new building product, you are mitigating any of these risks before it is widely available for use.

    “When you develop a material or plant material, it’s very important that you apply all three. So healthy accommodation, climate protection and sustainable resourcing.”

    A supply of cork

    Golden rule: When it comes to fossil fuels, leave it in the ground

    The natureplus label requires a product to be composed of at least 85% bio-based mineral materials or recycled materials. This is to exclude products that are primarily petrochemical based and ensures that the products aren’t damaging the environment or human health.

    The process utilises independent testing to ensure transparency and quality

    The Nature Plus Association (NPA) is the non-profit responsible for issuing the eco label. However, the assessment of the building product is carried out by a cooperative called the Nature Plus Institute (NPI). So the NPA sets the criteria and the actual testing is undertaken by the NPI.

    Tilmann recommends taking a closer look at which companies are issuing eco labels and check the transparency of their process. In the case of natureplus, the assessment is carried out by an independent body to ensure transparency and quality assurance.

    To test the climate impact of a product, a lifecycle assessment is performed. This looks at the A1, A2 and A3 stages of the building product, which refers to the upfront carbon emissions: from cradle to gate.

    When it comes to assessing the health impacts of a building product, there are two areas that need to be assessed: what material does the product contain and what comes out of the product? For example, the Eco Institute in Cologne will test the product for substances such as formaldehyde or Volatile Organic Compounds (VOCs). They will then put a sample into an airtight chamber and measure the emissions from the product over a 28 day period. In order to meet the natureplus standards, the product must not exceed very strict thresholds.

    Quality control is assured through the natureplus guidelines

    natureplus have strict testing standards which are replicated in a variety of different laboratories and testing sites. By having set standards and a precise criteria, the results can be guaranteed to be accurate and consistent.

    An Environmental Product Declaration (EPD) does not necessarily mean it is sustainable

    Unlike the natureplus eco label, an Environmental Product Declaration (EPD) just quantifies the environmental impact of a product and does not indicate whether these are positive or negative. The label in itself is therefore not a signifier of quality or sustainability and instead offers transparency. This is very much needed in the construction industry but does require further research to determine if the product is good or bad. The natureplus eco label instead tries to communicate quickly and clearly that this is a product you can trust to have a focus on health, climate protection and sustainable resourcing.

    “Communication is key and what we try to do is do it as simple as possible. So this is why we do this very, very big testing that we then put into one simple statement: this product is natureplus. So it’s really to make the complex communication as simple as possible.”

    The natureplus eco label is a good indicator that a company has strong core values

    Manufacturers must collaborate in the accreditation process by providing key information about performance, composition, etc. It also costs around 8000 euros to receive the label as well as an annual licence fee. The natureplus eco label is therefore a really good indicator of a sustainable product as in addition to the quality assurance, you also know the company has put in time and resources to achieve it.

    There are three primary types of labels out there and it is important to understand them

    Eco labels like natureplus, assess a product on the level of sustainability and should provide some tangible information about its impact and composition. The second type of labels are labels run by the manufacturers themselves. These labels will highlight some information about the product sustainability but they do the criteria development and assessment internally, which reduces transparency and lessens accountability. The third type of label refers to labels such as EPDs. As mentioned earlier, these are merely a declaration and it doesn’t say that this product really is environmental friendly or not. It is key to understand what each label means as each process has a different implication on the meaning of the label.

    “A very harmful product actually could get an EPD. It’s good that they do because at least they are transparent with the information, but yeah, it’s not an eco friendly product necessarily.”

    The Natureplus eco label is primarily based in Central Europe

    Tilmann explains that natureplus is an international label and certified products are widely available, but the majority of the products are produced within Centural European countries. Sadly, there are no UK manufacturers with a natureplus eco label yet but there is hope for the future.

    Exchanging ideas is crucial in the sustainable building sector

    natureplus is a European network and in the face of the climate crisis, it is crucial that we are taking inspiration from countries with innovative ideas. Tilmann explains that we can turn to the architecture of Turkey to understand how to using shading to combat overheating or to the Netherlands where an innovative, pre-produced facade that can be assembled within days has proven to be popular. By tuning into the different solutions from European countries we can pool our collective knowledge to tackle many of the challenges that face us.

    “Think global, act local”

    The ultimate goal is to have enough natureplus products that you could build an entire house out of them

    Tilmann explains that at present natureplus has certified approximately 600 different building products, from insulation to CLT timber.

    There is a list on the website of all of these products. However, if you need to gather some more information about performance, some useful databases to use along side the natureplus product list are 2050s Materials, First Planit Materials and Powerbook.

    Find out more

    Visit the website of natureplus

    Alliance for Sustainable Building Products (ASBP)

    Transcript

    Download the transcript of this episode.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Like our Facebook page

    Follow us on X

  • HPH338: How to measure and monitor the performance of a home – with Luke Smith

    HPH338: How to measure and monitor the performance of a home – with Luke Smith

    Luke Smith from Build Test Solutions talks about making building performance measurement more commonplace, and how you can’t manage what you don’t measure.

    Interview with Luke Smith

    Luke Smith trained as an architectural technologist. He is now the Managing Director of Build Test Solutions, making building performance measurement and monitoring more accessible, affordable and mainstream.

    Being able to measure anything doesn’t mean you should measure everything

    The availability of low-cost sensors means there can be a risk of going too far with measurement. For a building that could stand for 50 or 100 years or more, building fabric performance is fundamental.

    Building fabric performance measurement includes the whole building heat loss rate (heat transfer coefficient), airtightness, and U-values of the walls, floors and roofs.

    Performance measurement is suitable for new-build and retrofit

    Non-invasive measurement techniques can be done at any time and with any occupancy, so they are equally suited to retrofit projects and new-builds.

    Checking the performance of new buildings immediately post-completion is ideal, but measurement can also support recommendations for single measures like heat pump installation or relatively modest fabric upgrades.

    Measurement is just one of the three ‘M’s

    Keep in mind the distinction between modelling, measurement and monitoring – the three ‘M’s.

    • Modelling is where you start before building anything. As a lot of it is based on prediction, its outputs will only ever be as good as the inputs.
    • Measurement checks the as-built performance of the new-build, or measures the before and after performance of a retrofitted building.
    • Monitoring is an ongoing process once the building is occupied.

    The three are interlinked. For example, by measuring in situ U-values, you can check that the insulation is doing its intended job. Those measurements can go back into the model and help to calibrate it, so you have a better idea of how the building should perform. The fine-tuned model can then be compared to monitoring data, helping to identify issues and suggest remedies.

    Smart HTC energy inputs and outputs

    Measuring heat transfer coefficient is a good place to start

    Understanding the building’s overall thermal performance won’t tell you specifically where heat is being lost, but it’s a good barometer of how well the fabric retains heat.

    Build Test Solutions uses a technique called Smart HTC, based on inputting internal temperature data and the total energy consumption over a three-week period into an algorithm. Smart HTC can be done without disrupting the day-to-day occupancy of the building.

    SmartHTC IHD

    Smart HTC charts

    Blower door fans aren’t the only way to measure airtightness

    Build Test Solutions uses a technique based on compressed air to measure airtightness. ‘The Pulse’ releases a burst of air and the instrument measures the pressure response – how quickly the background pressure in the building elevates and then recovers back to the original condition. It’s a quick and non-invasive way of measuring air leakage rate. And, because it’s at low pressure, it doesn’t exert high push and pull forces on the building fabric.

    Pulse air permeability testing

    In-situ U-value measurements can help to find specific issues

    To understand specifics, in-situ U-value measurement gives the heat loss through individual building fabric components. This is the next step if the whole building heat loss measurement has identified an issue and you’re trying to find exactly what the problem is. Taking several readings across the area of a floor, wall or roof helps to show if it has been constructed consistently.

    H3DU values

    Ongoing monitoring can be based around energy consumption or air quality

    From an energy consumption perspective, you could be looking at total energy consumption at the meter, or at a sub circuit level – lighting or ventilation systems, for example.

    In terms of health, the main things to monitor are relative humidity, carbon dioxide levels and ambient temperature. But you can also get more in-depth, especially if family members have respiratory illnesses or you’re keen to protect young children. Air quality aspects like particulates, VOCs, radon and carbon monoxide can all be monitored.

    What action will you take based on monitoring data?

    The main thing to ask is: how often will you look at data you collect? What action will you take based on it? The novelty of simply having data can wear off.

    At the same time, devices that can provide warnings – around carbon dioxide or humidity levels, for example – might provide the impetus for behaviour change.

    An example of a basic portable temperature and relative humidity logger

    Monitoring sensors can be portable, semi-permanent or hardwired

    Broadly, three categories of monitoring technologies are available.

    • Portable devices are battery powered or mains powered. They can be placed in a single, central location or you might move it throughout the home and check different rooms over different periods. Combined with an existing smart meter, you could begin to understand both energy consumption and air quality.
    • A semi-permanent installation might come from a company offering a monitoring platform. A central hub has multiple nodes connected to it. The sensors collect data across the home, all presented through a single dashboard.
    • A permanent system is hardwired and can be hugely complex – think a smart energy management system or home energy management platform, verging on home automation. For example, it might track internal humidity and trigger the ventilation system to boost, or open a window.

    Portable devices can be small and unobtrusive. Semi-permanent and permanent sensors can be integrated with the building fabric if they’re planned from the outset.

    A hardwired system is thousands of pounds, compared to a couple of hundred pounds for a portable sensor.

    Consider the Matter protocol if looking at monitoring platforms

    Matter is a universal communications protocol that allows devices to interface together. You could have a Matter-enabled smart thermostat, smart home speaker and EV charger, and they could all talk to one another and present you with information centrally.

    Devices can already give you a lot of energy consumption information

    The general direction of travel is for smart technology to give us a lot of monitoring information. EV chargers are likely to be smart, with an integrated metering capability. Heat pumps typically give the electricity they’ve consumed and the heat output they’ve delivered. Smart light bulbs, and other things like them, will come with a hub to track the energy they’ve consumed. Even without proprietary monitoring equipment it’s possible to get a detailed insight into the energy consumption of the home.

    Luke strongly advocates using a smart meter, to get gas and electricity consumption data broken down into 30-minute intervals. Consumer access devices (CADs) let you go further, even getting as granular as 10-second intervals. Shorter intervals can be useful if you’ve got solar panels generating during the day, or an EV discharging at night. It lets you track and understand what’s happening in more detail.

    Luke shares a few options for monitoring

    Portable monitoring options 

    These simple standalone devices are either battery powered or plug into the mains.

    Aranet4

    Airthings

    Amazon Air Quality Monitor

    Ikea Air Quality Sensor

    All of the above environmental condition sensors can be great alongside data from your smart meter, smart EV charger, and PV monitoring system. 

    Power metering smart plugs would also sit in this category.

    Semi-permanent monitoring options

    These are typically offering the capability to link numerous sensors through a single central hub or gateway

    Open Energy Monitor

    Purrmetrix

    Shelly

    Permanent/fixed monitoring

    These are hard wired solutions where the monitoring layer may form part of a wider smart home management platform.

    Loxone

    Smart thermostats are also examples of basic hardwired solutions that can also typically provide temperature and relative humidity data  – Nest, Hive, Tado, Honeywell, Drayton etc.

    Find out more

    Podcast interview with Tom Fenton (testing the thermal performance of a house)

    Podcast interview with Jonathan Dixon (combining smart home technology with energy efficiency)

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Like our Facebook page

    Follow us on Twitter

  • HPH328 : Insulating internally with a thin layer of wood fibre board – with Martin Twamley from Steico

    HPH328 : Insulating internally with a thin layer of wood fibre board – with Martin Twamley from Steico

    Martin Twamley from Steico explains how to use breathable internal insulation, while avoiding the risks of condensation and mould.

    Interview with Martin Twamley

    Martin Twamley is Technical Director of Steico UK. Steico have been producing timber-based materials, predominantly structural timber and insulation materials, since the 1960s and selling them across Europe. Using only pine and spruce they make a number of different products, and will always provide guidance as to what the correct product would be for the required application.

    “Once people start using timber and understanding it, it’s a sort of material that you fall in love with, and you then change your building process.”

    The products have low embodied energy

    Structural products like I-joists were first used in the USA and the motivation was that it was the most sensible use of the raw material. However, as a natural material and one that goes through little processing it also has a low embodied energy, and will even lock up carbon.

    Laminating the veneers strengthens the product

    The I-joists are created from Laminated Veneer Lumber. They are made by peeling a tree, creating 3mm veneers, and then bonding them back together. This means that individual weaknesses are removed and spread across the whole product. The strength-to-weight ratio on engineered timber is then much greater than it is for solid section timber as you’re getting a much stronger product for less raw material.

    There is very little manufacturing waste

    Martin explains that the good thing about producing both structural and insulation products is that there is very little waste. For the structural timber they use the de-barking and peeling process. For the insulation materials they use chipping and milling. Therefore, what they can’t use for the structural timber they can use for the insulation. What they can’t use for the insulation they can use for producing their own pallets. And if they can’t use it for pallets they have a biomass power station where they can use it for electricity generation.

    UK housing stock has a need for internal insulation

    The UK housing stock is some of the oldest in Europe and is in desperate need of retrofitting. With a reluctance to insulate externally and change the appearance of this historic solid wall housing, internal insulation may be a better solution.

    The traditional way of doing this is with systems that try to block the moisture, rather than being able to control it. When you try to block moisture there can be an issue with getting it trapped inside the building instead. This potentially adds risk to the fabric of the building, because of mould and condensation problems.

    The Steico wood fibre internal insulation system allows water vapour in, controls it, holds it, and then lets it out again.

    Standard insulation installations are vapour closed

    These typically are the foil-backed polyurethane type materials that are either on a frame system or dot and dabbed onto brickwork. In theory they don’t let any moisture in, which is a good thing for the fabric. This can however lead to high moisture levels internally, so you might need to consider an MVHR for example. Mould will happen when warm air gets behind the plaster board and hits the cold wall surface. It might not even be until years later that the mould shows itself on the internal surface.

    “When people think about air quality, they generally think about external air, but we spend 90% of our time indoors. It’s the internal air that we’re breathing. So that’s what’s impacting our health.”

    These are the kinds of systems that tradespeople and DIYers are most likely to use, because they’re readily available. Also, homeowners are primarily just thinking about thermal performance in the winter. But actually, when you consider a holistic approach that takes into account all the possible issues, the material choice is incredibly important.

    Internal insulation doesn’t have to significantly impact on the room size

    Martin talks about applying a thin layer, typically an optimum amount of 40-60mm. Even in relatively small rooms that’s an amount that won’t really be noticed.

    What works for one building, won’t work for every building

    What works for one elevation of a building might not even work for a different elevation of the same building, because of different weathering exposure. This is why it is so important to have an assessment done, particularly if you’re looking for a really low U-value. Martin explains that generally speaking a 40mm or 60mm board on standard brick will work in the majority of situations.

    Take the wall system back to bare brickwork if possible

    The wall system should be as breathable as possible. That means that you don’t want anything on the internal side that hinders water vapour movement, such as impermeable layers, cement-based plasters and renders, and paint layers.

    The external face is also important to consider (such as renders and re-pointing), because this is where the majority of the water is coming from.

    With this natural, breathable approach, there is a full bonding layer (typically a lime based product) between the insulation and the wall. This is in contrast to a traditional approach that would have a cavity. The fact that there is no cavity means that there is no collection of liquid water, which is what leads to mould and condensation issues. Instead, any moisture is either passed onto the brickwork and out the front, or it can go back to the inside.

    Pay particular attention to the critical areas

    Window reveals are particularly important. If you have a warm wall surface, then the window reveal will be the coldest area. If you don’t insulate into that reveal then that is where all your condensation will form. Martin suggests that with a 40mm or 60mm on the wall, a 20mm board on the reveal will be fine.

    Another critical area that could be overlooked if somebody is insulating ground and first floor, is the void where the floor joists connect into the wall. These can be cold spots where condensation will be much more of an issue than it was before. To prevent this, you can tape around the junction of the joists to the existing wall. This stops the route for convected airflow into the wall.

    Where you have internal walls connecting with external walls can also be problem areas. If you’re insulating the external wall, then the corner of that internal junction can be quite cold. Steico make a wedge-type product of thinner insulation that can go into the corner to stop the condensation risk.

    There are useful resources available

    Martin makes reference to The Guide for Sustainable Renovation, by The Pebble Trust, as being a valuable resource for anyone taking on a retrofit project. It gives advice with a holistic approach that considers all of the moisture risks involved.

    The carbon storage element of materials is often overlooked

    A frustration for Martin is that in the UK he thinks we tend to be quite product agnostic. It is very much that if you achieve a certain performance level then it doesn’t matter what you use to to get there. He compares this with Bavaria, Germany, that has a new system brought in by local government. They are offering a 500 Euro grant for every cubic metre of biogenic carbon locked up within the fabric of the building. In the UK we have U-value targets, but nothing that looks at the amount of carbon stored within the fabric, or the type of material that is used.

    Find out more

    Visit the website of Steico

    Follow Steico UK on Twitter

    See Steico wood fibre insulation being used on Buckinghamshire Passivhaus (a PH15 project). Join The Hub to access our in-depth video case study.

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Rate and review the podcast on Stitcher

    Follow us on Facebook

    Follow us on Twitter

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

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

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

    Interview with Es Tresidder

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

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

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

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

    A good location can lead to a more sustainable lifestyle

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

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

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

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

    Never be afraid to get input from people with more experience

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

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

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

    Make sure you have the right tool for the job

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

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

    Be prepared that some things may not go to plan

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

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

    Working alongside a building team presents challenges

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

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

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

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

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

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

    This radical retrofit will lead to a healthier home

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

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

    Removing the roof was radical

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

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

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

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

    DIY is time-consuming and exhausting

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

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

    Top tips

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

    Find out more

    Visit the website of Highland Passive

    Visit the website of John Gilbert Architects

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

    Transcript

    Download a transcript of the interview with Es Tresidder

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

    Please connect with us

    Subscribe, rate and review us on Apple Podcasts

    Rate and review the podcast on Stitcher

    Like our Facebook page

    Follow us on Twitter