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Tag: airtightness

  • HPH394: Could you automate air sealing on a house build?  – with Hugh Franklin

    HPH394: Could you automate air sealing on a house build?  – with Hugh Franklin

    Hugh Franklin from Aeroseal UK explains how the airtightness of a building can be improved using a water-based, low VOC atomised polymer which is delivered when the building is pressurised. This simpler approach speeds up the process of air sealing and gives real-time feedback on the airtightness score.

    Interview with Hugh Franklin

    Hugh Franklin is the Head of Operations at Aeroseal UK, where he leads the development and deployment of the AeroBarrier airtightness system. His career began in archaeology, spending years de‑constructing historic buildings and extracting lessons about passive cooling, solar shading and other age-old strategies. Those insights sparked a shift toward eco‑construction, where he focused on scaling sustainable building practices before narrowing his expertise to airtightness over the past eight years. Today, Hugh combines his deep appreciation for traditional building wisdom with the latest technology to help builders achieve high performance homes.

    The ‘mist’ sealant automatically hones in on the leaks

    Airtightness is a key characteristic of a high performance home, but airtightness strategies can be labour‑intensive using boards, membranes, tapes, liquid paints and so on. Hugh describes how a mist of low‑VOC polymer sealant, delivered under pressure, automatically seeks out leaks and creates a uniform seal. This reduces material waste, shortens installation time, and delivers measurable improvements in the building’s air‑leakage score.

    “We create a fog, a mist of a water-based low-VOC sealant… the sealant is drawn towards those leaks by the escaping air.”

    It is possible to dial‑in the airtightness you want

    AeroBarrier is introduced into a building during a standard blower‑door test. When the building is pressurised the mist travels through any gap or crack, collides with itself and solidifies around the leak. Because the product is an acrylic polymer that is 60–80 % water, only a few litres are needed for a typical 200 m² home. The sealant does not expand; it accumulates only where airflow exists, allowing the airtightness score to be dialled down to the exact target.

    The building is carefully controlled during misting

    Everyone steps outside while the mist is applied and it doesn’t take long. Workers inside wear appropriate respiratory protection, but the low‑VOC formulation produces minimal fumes. After sealing, the space can be re‑entered within 30–60 minutes once the mist has dried, making the process practical for busy construction sites.

    “We control the space during the install, much like if you’re doing an airtightness test.”

    Long‑term durability is proven in the lab and the field

    AeroBarrier has undergone lab testing up to 5 000 Pascals (hurricane‑level pressure) and shows no degradation after 50 years of simulated ageing. Field studies report only a 1–2 % loss of airtightness over 25 years, confirming that the polymer remains flexible and effective long after installation.

    Automation works best when paired with manual detailing

    The system can seal gaps up to 10 mm. Larger openings generate a visible “white halo” during misting, signalling that manual patching is required. This hybrid approach lets builders concentrate on the biggest defects while AeroBarrier handles the multitude of smaller, hard‑to‑detect leaks.

    “AeroBarrier will try and seal that, but it will start to form a white halo around a hole that’s quite large… you can walk around the building… and find those gaps and then fill them manually.”

    Real‑time feedback turns airtightness into a visible metric

    A key obstacle in airtightness is the lack of instant performance data. AeroBarrier integrates with the blower‑door test, displaying the current ACH (air changes per hour) score on a screen as the mist seals each leak. This immediate feedback lets site teams see which details are performing well and which need attention, fostering ongoing learning and improvement.

    There is an optimal moment to apply the sealant

    For new builds, the best time to apply the mist is post‑first‑fix, after windows, glazing and major services are installed but before interior finishes. In retrofits, the building must be sufficiently sealed to become a “pressurisable box”; otherwise, the mist will escape and the process loses efficiency. Coordinating with the contractor to schedule the test at the right stage is essential for success.

    “We want the building to look as much like a porcupine as possible. Post first fix is really when we want to come in.”

    A draught-free home will deliver savings

    AeroBarrier is priced at roughly £12.50 per square metre of floor area. For a 200 m² home, material costs are about £2 500, plus labour. Hugh notes that the return on investment typically appears within three to five years through reduced heating and cooling demand, especially when moving from a standard Building Regulations home to the Passivhaus standard.

    Achieving airtightness this way requires a slightly different plan

    Hugh says that their best clients keep an open mind about the approach to airtightness. It’s much better to have a talk upfront about how to get the most out of the system. For example, setting clear tolerances early on will avoid unnecessary work (e.g., keep penetrations ≤ 5 mm for high‑performance builds). Builders, plumbers, electricians and ventilation suppliers need to understand these limits and coordinate their work to avoid unintentionally creating new leaks. Brief on‑site training and visual guides help keep everyone aligned.

    Once achieved, airtightness must be preserved

    If a great airtightness result is achieved at first fix this is not a cue to rest on your laurels. Throughout the project it’s important that everyone who is working on site understands the airtightness line. Typical mistakes might include cutting through an airtight membrane without making good afterwards. Hugh shares a couple of examples. When electricians are installing recessed lighting they might not quite have enough room so they cut through the membrane. Also when it comes to adding services, like cables, pipes and ducting, a similar problem can occur. Because the airtight layer is often invisible, any breach can dramatically reduce the airtightness of a property. Scheduling blower‑door tests at key points and encouraging a culture that reports issues without blame can help maintain a good airtightness score.

    Scaling airtightness for mass‑market housing

    Hugh believes that making airtightness cheap, fast and easy to verify is the key to bringing low‑energy homes to the broader market. By combining automated sealing with clear performance metrics, builders can deliver consistent results without needing specialist airtightness gurus on every site. The goal is to demystify airtightness, turning it from “black magic” into a routine part of construction.

    Find out more

    Aeroseal UK

    Transcript

    Download a transcript of this episode.

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  • 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)

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  • 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

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  • HPH325 : What reduces the performance of insulation? – with Mark Siddall

    HPH325 : What reduces the performance of insulation? – with Mark Siddall

    Mark Siddall explains how thermal bypass – or air movement around insulation layers – might impact a self-build or retrofit project.

    Interview with Mark Siddall

    Mark is a Passivhaus specialist who has been on the podcast before, talking about avoiding the risks of poor ventilation and his ‘forever home lifestyle’ framework.

    His practice LEAP operates from County Durham and Newcastle. He is also a technical adviser to the Passivhaus Trust and the AECB. He has written a paper on thermal bypass risks for the Passivhaus Trust.

    There are many types of performance gap – but energy is often the focus

    For Passivhaus buildings, the focus tends to be energy performance rather than other factors like air quality. Passivhaus projects actually close gaps in predicted performance, which can’t be said for other approaches. The methodology has got better quality assurance processes, which avoids risks that might otherwise arise.

    Insulation has to be specified correctly for it to deliver energy performance benefits

    Dealing with energy performance often means the thermal performance of the building fabric. Three variables influence whether insulation works or not.

    • The material itself.
    • Whether the material is specified sympathetically for the construction method used.
    • Whether the material is installed properly.

    Get those variables aligned and the evidence shows everything works properly.

    An example of an air gap when using blockwork and rigid PIR insulation

    Choosing insulation for cavity walls

    Cavity wall construction is very common in the UK. A Passivhaus designer will question if the usual foam insulation solution is sympathetic to the method of construction.

    Blockwork features mortar joints, and mortar is squeezed during installation. That creates snots which project into the cavity and stop the insulation sitting against the face of the blockwork. The resulting small air gap is enough to completely undermine the thermal performance of the insulation.

    Mortar snots can be cleaned off, but that might not happen all the time. A mineral wool solution is more flexible and capable of dealing with subtle deviations, so it’s a more appropriate insulation for a cavity wall. It’s also used to the full depth of the cavity, which helps to reduce the risk of air movement.

    Mineral wool fully filled cavity at Steel Farm Passivhaus

    Airtightness is about moisture as well as heat loss

    Part L of the Building Regulations deals with heat loss and prescribes a specific level of airtightness. Part C talks about moisture and only says things should be fairly airtight. There’s no numerical target related to moisture, and that’s a problem.

    The Passivhaus standard, and research conducted in Canada, both confirm that airtightness of 0.5 or 0.6 air changes per hour at 50 Pascals is needed to avoid damage to timber structures (such as roofs or framed walls). That’s an air permeability of around 0.5, compared to the Part L target of 8.0.

    Good airtightness alone doesn’t guarantee insulation performance

    From the external side of the wall, wind tightness stops the wind blowing through and around the insulation, which wicks away heat. It’s not something that can be tested on site, however. As a rule of thumb, the quality of workmanship needed for a wind tight layer is similar to that needed for the airtight layer.

    Fully encapsulate insulation between the air and wind barriers

    Convective loops can happen around insulation just from the temperature differences between the warm and cold sides of the wall. We can avoid that by properly encapsulating the insulation between a notional air barrier and wind barrier.

    Using the same cavity wall example as before, a good build-up might be brickwork or stonework on the outside face. Then a 300mm cavity full filled with mineral wool insulation that’s built up in two or three layers. The inner leaf is blockwork, which is plastered internally.

    The plaster acts as the air barrier, and the brick or stone is the wind barrier. The cavity is fully filled, so the insulation is encapsulated and has no air gaps around it.

    Rainwater is the dominant moisture problem to tackle

    Cavities were introduced to walls to act as a capillary break and stop water being drawn through from the outside. Any water getting through the outer leaf drained down the inside face of the cavity and out through a weep hole.

    A very narrow cavity fully filled with insulation carries a risk of rainwater bridging across to the inside of the building. That risk reduces with a wider cavity. Passivhaus design requires wide cavities and, with good workmanship and no mortar snots, any risk from driven rainwater is mitigated.

    Installing the cavity insulation in layers means that if any water gets through one layer, it can still be pushed down and back towards the outside.

    Think about how wall ties affect performance too

    Cavity wall ties help to provide structural stability, but are also a repeating thermal bridge through the insulation layer. Mark specifies Teplo wall ties instead of stainless steel ones. Stainless steel ties have a larger physical dimension and a higher conductivity, whereas Teplo ties are thermally broken.

    Design calculations usually assume perfect installation

    On most projects, architects contact insulation manufacturers for U-value calculations. The manufacturer never asks what quality of workmanship is being specified. Instead, they assume perfect installation, which requires certain tolerances on site.

    When those tolerances aren’t achieved and workmanship is less than perfect, which is the case on every building site, then air gaps are the result. Materials haven’t been specified to work sympathetically with one another and the predicted U-value isn’t achieved.

    Timber frame construction can help to address performance gaps

    From inside to outside, a typical timber frame construction capable of producing good results would be:

    • Plasterboard.
    • Service void, which may or may not be insulated (ideally not).
    • Airtight layer.
    • Engineered I-beam filled with cellulose insulation.
    • Wood fibre insulation on the outside.
    • Wind barrier membrane.
    • Drained cavity, acting as a capillary break.
    • Rain screen on the outside face.

    Compared to this build-up, performance gaps can occur because standard industry timber frames don’t have the wood fibre layer, don’t use engineered I-beams, and are less likely to feature a service void. Services penetrating the air barrier will allow moisture from inside the house to get into the timber frame, potentially causing moisture damage.

    One area they tend to do well in is using 150mm thick insulation in the 140mm frame. Because the insulation is that little bit bigger, it’s compressed slightly and ends up being snugly sandwiched between the air barrier and wind barrier. There’s less risk of convective loops.

    Improvements can always be made to reduce performance gaps

    Research from places like Sweden and Canada is showing that, in the construction described above, moving the wind barrier behind the wood fibre (which might be just 20mm thick) could significantly reduce the risk of condensation.

    The climates are different to the UK, so the conclusion might not be the same here, but it shows there are still refinements that can be done in Passivhaus timber construction to make it even more resilient than it already is.

    Air movement is the issue across all build systems

    All construction technologies need to address the key issues of building physics. With straw bale, for example, a lime or clay plaster on the inside can provide the airtight layer. There are other subtleties and complexities, but it’s a case of limiting air movement through, and within, the wall construction so the building performs as predicted.

    An example of a warm roof (Shepherd’s Barn)

    The same principles apply to roofs…

    …although it depends what type of roof it is. A warm roof construction is very similar to the timber frame walls, just at an angle. The tiles or other roof covering replaces the rain screen.

    A cold roof, with insulation at ceiling level and the attic space above is risky to deal with from a moisture perspective. Information Mark has seen suggests one-third of the moisture that transfers into the roof space could condense on the roof structure. It has to be possible to remove that, using a vapour permeable underlay.

    Ventilation can also be used, but there are reasons why that may or may not be preferable or doable. Then it’s necessary to look at the eaves detail and the risk of wind washing. Air comes into the loft at higher speed, so special details are needed to help protect the insulation at the edges.

    The important advice is to keep things simple

    Details have to be simple to make them buildable. Then they can be replicated from person to person, site to site, and house to house.

    Make sure you have an air barrier and a wind barrier, and that you encapsulate the insulation. Do that and you’re on the right path.

    The ‘Thermal Bypass Risks’ paper on the Passivhaus Trust website provides solutions. It includes tips and tricks for designers and architects to help mitigate thermal bypass. Each section features accessible takeaways that could also be used by self-builders.

    Find out more

    Visit the website of LEAP

    Follow Mark Siddall on Twitter

    Read Mark Siddall’s paper on Thermal Bypass Risks

    Watch the documentary case studies at PassivhausSecrets.co.uk

    Transcript

    Transcript-of-House-Planning-Help-podcast-episode-325-Mark-Siddall

    Dear Evil Engineer

    Thank you to Stephen Miller in Oxford for sharing this with us. The Institution of Engineering and Technology has a bit of fun from time to time with their Dear Evil Engineer series. Villians write in for advice on their diabolical plans.

    So how many leopards do I need to heat my home? And they even consider homes that are built to Passivhaus standard!

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  • HPH324 : Why robust planning is vital for a home retrofit in stages – with Alan Budden

    HPH324 : Why robust planning is vital for a home retrofit in stages – with Alan Budden

    Alan Budden explains how a phased retrofit might work and what preparation is required. He also shares how he’s retrofitted his own home, which includes trialling an innovative roof solution.

    The house (after the retrofit)

    Interview with Alan Budden

    Alan has been on the podcast before. Last time he explained how simple design decisions can impact on energy performance and cost.

    In this session he reflects on his own retrofit which is getting towards the final stage.

    Alan’s practice Eco Design Consultants is well versed with deep retrofit and were the architecture firm leading the Kinver project.

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

    If you have the funds, tackle a retrofit in one go

    Nobody ‘chooses’ to do a staged retrofit because it’s a better option to do all the work in one hit.

    Not only will it be cheaper overall (for example tradespeople might have to make a few more visits during a phased retrofit) but the disruption will also be minimised.

    And from a planning perspective it will be simpler too.

    There’s lots of junctions you have to consider in terms of how it’s going to be weathered and work during that stage, as it could be six months, it could be 10 years between stages. That’s one of the issues. So you end up detailing things, then for the final construction detailing it back.

    Retrofitting in stages is a way to progress with the money you have today

    Recently Alan has noticed a lot more enquiries from young families who are keen to upgrade their homes.

    Unfortunately they lack the funds for a comprehensive retrofit so Eco Design Consultants recommend tackling it in stages.

    The most important aspect is to have a whole house plan before you start.

    A staged retrofit could allow you to stay put during building work

    Depending on the size of the house one benefit of a phased approach is that you might be able to move around the house while the work is being done, thus save money on moving out and renting accommodation.

    Retrofit at an appropriate stage in the maintenance cycle

    All houses require maintenance and upgrading so there will naturally come a point where you’ll be spending money on your home anyway.

    The house still had single-glazed windows

    The single-glazed windows were not fit for purpose and had been something Alan had wanted to change ever since he bought the property. While he could have upgraded to double-glazing he bided his time so that it would be a switch straight to triple-glazing. His cladding was also tired and needed replacing so doing all these things together can contribute to the project costs.

    The front of the house (before the retrofit)
    The back of the house (before the retrofit)

    Think of a deep retrofit as creating a house for life

    A deep retrofit is significant work so it’s unlikely that you’d just want to sell the house straightaway afterwards. So you should be trying to make the house work for you now and into the future.

    Think carefully about how you want to live in the house. Could you also add a bit of value (by increasing floor area, if needed)?

    Can the house shape be simplified?

    Alan wanted to do the design work himself

    Despite having an architecture practice at his disposal, Alan thought the ethical approach was to do the design work and modelling himself. Consequently progress was slow, being confined to evenings and weekends.

    Modelling the house in PHPP is a key step

    Alan says that after deciding how you want to live in the house and optimising the layout, the next step is to begin modelling it in the Passive House Planning Package. Setting an energy target for the project, such as the Passivhaus retrofit standard EnerPHit, helps inform decisions about insulation, windows, etc.

    The shape (or form factor) of the house was improved

    Where the first floor was slightly smaller than the ground floor Alan decided to square up the building. This increased the floor area, allowing for a new dressing room and increasing the size of the en suite. but also simplified the shape of the building.

    Alan’s knowledge meant he could optimise his approach

    When selecting materials Alan was always looking at a balance between cost, performance and embodied carbon.

    I looked at some interesting things with the external wall upstairs. Timber frame work projects off the wall with GRP brackets with just ordinary cavity wall insulation inside. So I’ve looked at the DriTherm 32, the DriTherm 36 and a couple of others, so it’s different types of mineral wool. And as it was less… the thermal conductivity was worse, the density was less, and the embodied carbon was less and the cost was less. So trying to optimise how thick the insulation was, and which ones I used was quite interesting. And depending on what sort of brackets I could get as well for the timber frame. So it was quite a complex lot of options.

    Think how you can stretch funds

    Alan planned to do parts of the work himself to save money and therefore, hopefully, take the project further.

    He was also planning to test a new roof system which would be manufactured off site and placed onto the existing trusses, but it had a few teething problems. Knowing there would be a delay in the programme there was nothing to be gained by hiring builders to get through the work quickly.

    The builder was happy to step in as required

    Alan describes how he and his family put on the membrane (from the scaffolding). The builders then came and put the brackets on and the timber framework. And then it was back to Alan and family to fill it with insulation. And so on.

    After taking the roof off the utility room and building upwards, they stripped the tiles off the rest of the building and made a few adjustments in preparation for the new roof cassettes.

    A stick-on airtightness membrane, Siga Majpell 500, was installed.

    A multi-purpose roof was manufactured off site

    Alan has always been interested in how retrofit might be tackled at scale and as such he’s been part of a group developing an innovative roof panel system.

    With funding from Innovate UK the project has progressed and he has become the guinea pig for the first full installation.

    The idea was to develop a structural roof panel that includes PV and solar thermal, using that to heat the house.

    Off-site manufacture comes with benefits

    Using a crane the panels were lifted into place in just one day.

    This is a big health and safety benefit because it reduces the amount of time that people are working at height.

    Alan comments that making the roof panels have more than one purpose should bring about some economies of scale.

    Unfortunately some of the technology underneath the panels that was being used to cool them didn’t work as planned, so they are looking at an alternative and hoping to lift off two of the panels off and replace them with new ones. Then they can get them plumbed in and see how much energy they are reaping from the roof and how that’s helping to improve the performance of the PV.

    Project delays meant Alan was without a roof for 6 months!

    With development delays and then the pandemic Alan was caught in a tricky situation. He had taken off his old roof, added a membrane and then discovered the roof panels were not ready!

    The manufacturers of the membrane normally suggest that it can be exposed to the elements for up to a month.

    So Alan had a challenge on his hands, particularly when a big storm came along.

    My roof was left exposed for just over six, including the winter, which is not the best of times, which meant that I was getting condensation forming on the inside because the insulation was planned to be put on the outside and I had some insulation left in the loft to keep us a little bit warm in the winter. So I was having to mop it down, which shows you really, the amount of water I was taking off was quite considerable. At the worst times, I almost had a bucket full of water. I was at the end of it with my mop! And it does show you how much moisture you’re putting out as a family. And if that’s going to condense somewhere that could cause all sorts of problems. Luckily I could see it, I could deal with it. And now obviously that’s gone away.

    The membrane did survive and seems to be doing its job.

    Get the MVHR online as soon as the house becomes airtight

    In a new build the MVHR might be commissioned towards the end of the process but in a staged retrofit it needs to go on sooner, otherwise moisture and CO₂ will build up.

    The only downside of that is you will probably go through more filters as they get clogged up with the dust and the dirt from both the outside and the inside. Alan has been switching off the unit altogether if there are particularly dirty or dusty jobs going on.

    The insulation will go internally on the ground floor

    Alan wanted to keep some of the brickwork visible externally to match other houses in the estate, which means an internal insulation strategy is required downstairs.

    The windows downstairs will open outwards to maximise insulation on the frames

    All the windows upstairs have been changed because they went within the external insulation so they’re opening inwards. On the ground floor we’re doing internal insulation and those windows can open outward so we can maximise the insulation onto the frames on the insides. So there’s a number of windows downstairs still to be done. I did, we did take a few opportunities to insulate some of the windows on the ground floor, for instance outside our snug and the downstairs toilet because there’s some external cladding there with some vertical battens instead of horizontal just to emphasise… a bit of architecture! And also squeeze in a bit more external insulation.

    There’s added motivation as they near the end of the project

    The final stage of the project will be to insulate internally on the ground floor and replace the windows.

    One of the things that’s happened because of the extended programme is that we’ve been able to keep going. We weren’t necessarily expecting to do the ground floor stuff straightaway but it’s carrying on now! And because upstairs is so much warmer than downstairs, it’s really given us an emphasis to say we need to get this done. You realise the difference. Generally upstairs has been about three to four degrees warmer than downstairs. And that shows all the Passivhaus physics that air moves when there’s three to four degrees difference.

    The builders will come back to replace the windows

    With a house that’s getting warmer as the project progresses, the builders will be coming back to install the windows.

    This will get the changeover done quickly.

    Then it’s back to Alan and family to tackle the internal insulation room by room.

    So we’ll put some studwork up, insulate it, membrane it, re-plasterboard and finish it off. And also on the ground floor, what was going to be phase three that I think might happen at the same time is the floor insulation. The plan is to dig up the screed, put down a phenolic insulation and the board on top.

    A preliminary air test was conducted before the roof went on

    Having installed all the airtightness membranes as a family, Alan wanted an airtightness test before the roof panels went on.

    There were a few reasons for this. While they are always interested in an overall score, it’s more about identifying key leakage hotspots that can then be fixed.

    As with the Kinver project, once the roof is on there will be little hope in fixing leaks in this area.

    That’s why attention to detail is important. The number on this first test was 1.7 air changes per hour at 50 Pascals.

    Biggest risk with retrofit in stages is having to redo work

    Alan says one takeaway from the project is the importance of a well thought out initial plan.

    One thing I’m not enjoying quite so much is in our utility room and kitchen, I had already insulated some of the wall there with 50mm of polystyrene, mainly because at that stage, I was worried about the interstitial condensation. So I was limiting it to what I could do. But because now I’m insulating some on the garage side as well, I can increase the thickness of insulation internally. So I’m having to take out some insulation to put different stuff back in, which is a little bit frustrating to be honest. So get the whole plan done, make sure that works, and then do bits towards it, because that way you’re not going to be replacing those bits.

    Find out more

    Visit the website of Eco Design Consultants

    Follow Alan on Twitter

    Transcript

    Transcript-of-House-Planning-Help-podcast-episode-324-Alan-Budden

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  • HPH314 : Getting a self build over the finish line, despite setbacks – with Mike Coe

    HPH314 : Getting a self build over the finish line, despite setbacks – with Mike Coe

    Mike Coe gives a final update on his now complete Portree Passivhaus, that has seen budgets stretched, contractors disappear for a year, and a Covid lockdown!

    Interview with Mike Coe

    Mike Coe is a returning guest to the podcast. We have been fortunate enough to speak with him about his previous self build, Cropthorne Autonomous House, and have been following his progress since moving to the Isle of Skye to build Portree Passivhaus with his partner Lizzie. Having been in the house for a year now, we pick up where we left off three years ago, in episode 259 when the house was almost watertight, and find out whether Mike has managed to be as hands-off with this project as he had intended!

    Mike had always intended to do the MVHR installation and electrics himself

    He had started on the MVHR installation as soon as there was enough building there for him to work on. The main ducts that bring the fresh air in and take the exhaust air out, went in almost at the foundation stage, as they were assembled as the wall was being built that the ducts pass through. This way it meant they could be built into the wall, rather than having to cut out a large hole afterwards. He also started channeling out for power points before the concrete blocks were even up to first floor level.

    The specification of the MVHR was important for Mike as he wanted to build this house with no heating system whatsoever. They selected a system made by Nilan, which also contains a micro heat pump. It’s only around 60 or 70 watts, but it effectively aids the heat extraction process and makes it more efficient. It means that in the winter the heat pump comes on when the temperatures dictate it, making the incoming air temperature slightly warmer, and in the summer it provides a very small amount of cooling.

    Their only other source of heating is from a single bar electric fire which they’ve used infrequently, just for the odd hour here and there.

    It maintains a comfortable temperature

    The internal temperature on the night they moved in was just 11 degrees (with a raging storm and a power cut for good measure!) But once Mike got the MVHR up and running a couple of days later, and they had a week or two of sunshine, and with the effect of the two of them living there, it took just a couple of weeks for the temperature to rise to 21 degrees. Since then, they have been pleasantly surprised at how well it keeps a steady and comfortable temperature, even more so than the Cropthorne house, despite its larger form and having been less fastidious in the attention to Passivhaus detail. Mike suspects this is because of using the concrete blocks which, as well as providing the structure of the building, also act as a thermal store. He is conscious that the use of the concrete blocks and steel means it has higher CO2 emissions from the manufacture than that of a lightweight timber structure, but this was primarily dictated by the planning department.

    Mike’s previous Passivhaus experience paid off

    With a contractor and architect that didn’t have experience of building a Passivhaus, Mike found one of his roles on site being that of quality control. When it came to airtightness tape, he was able to show them how the standard builder’s merchant tapes would just tear like paper, yet the Passivhaus airtightness tape was incredibly strong and flexible.

    They didn’t mind and were happy for Mike to take on other pieces of work, such as some of the carpentry, especially as he and Lizzie were on site doing the MVHR and electrics anyway, and it meant the workload for their men was reduced.

    It took twice as long to build as planned

    The original plan was for a 15 month contract build period, but at the 10 month stage the contractor got called away to work on a 25 bedroom hotel extension, leaving just Mike, Lizzie and a freelance bricklayer to carry on with the work. This meant an incredibly frustrating almost year-long wait while the hotel project was finished, which unfortunately then coincided with the first Covid lockdown.

    “So there we were, with another three months added on to the almost year long delay due to the hotel build. The hotel extension was sitting there virtually complete, but they couldn’t open it because of everything was shut down because of Covid, whereas our house was nowhere near complete and nobody could work on it except me.”

    Mike managed to use that time as productively as possible to keep the project moving forward. Without being able to access new building materials as the merchants were closed, he dismantled some of the temporary stairwells that the contractor had put in so he could use the timber for building the stud partition walls. He used all the plasterboard that was laying around that he could, rescued timber that had been thrown out and used that for the stud walls, and also managed to build a new desk. Psychologically he found all this beneficial as it felt like progress was still being made.

    In total, the project took around 30 months to complete.

    Money became very tight

    With the planning department selecting the most expensive option, they always knew that the budget was going to be tight. In addition to the overruns caused by the lockdown, a number of other bills came in that caused them to go over by £34,000. This included £8,000 to install a water pipe from the mains halfway up the hill, rather than being able to connect from the supply of the neighbouring bungalow that they owned and were living in, and £750 for a tree survey to make sure that the pipe wasn’t going to damage any tree roots!

    As they were running out of money and with cash being tied up in the neighbouring bungalow until it was sold, they had to take on more of the work than they had ever intended to do. Mike had been unimpressed with the plumber who had done the first fix, so ended up rectifying some of his work and also did the second fix plumbing. This meant he plumbed the washing machine, kitchen sink, dishwasher, and the fit-out of all the bathrooms.

    With great reluctance, as it is a job he and Lizzie particularly dislike, they also ended up doing most of the decorating themselves.

    One year on, there are problems to rectify

    Having been in the house for a year, they are currently in the snagging period where the contractor will rectify some of the problems that crop up. Their contract allowed them to withhold a small percentage of the total payment, which will be paid once these have all been sorted. However, there are other problems which Mike intends to take on himself.

    The door in the lower ground floor porch was never properly adjusted and would stick and not shut fully. When he got round to looking at why this was, Mike discovered that it was actually causing a serious damp problem. The damp had resulted in the hinges corroding, with the adjustment screws for the doors then being impossible to turn.

    Something else that Mike will need to tackle, is an issue with the windows leaking. As they weren’t a standard specification that the contractor was familiar with, they installed them but weren’t confident to set them up, instead leaving this to Mike to organise. However, with all the other jobs and distractions going on, this got pushed lower down the list. With the driving rains they receive, several of the windows subsequently leak. Thankfully there are no serious structural leaks though, and when all the adjustments to doors and windows have been carried out then hopefully that should be an end to those problems.

    During a period of extremely high winds recently, part of the zinc capping that goes around the roof parapet was torn off. Fortunately it doesn’t threaten the structure of the house in any way and it’s still watertight, but it’s something else to add to the list of jobs.

    He has some carbon-saving projects lined up

    Now that they have freed up their cash by selling the neighbouring bungalow, and once Mike gets over a certain amount of self-builder fatigue, he is keen to make headway on some other projects.

    The first is installing a PV array that will make the house run more efficiently, as it will contribute to hot water and charging their new electric vehicle.

    He is also in the early planning stages of putting a micro hydro generator (a little water turbine) into a stream that runs down through their site. If it works it will likely only generate around 100-150 watts per day, but that will be for 24 hours a day and virtually through the whole of the year.

    He is adamant this will be his last self build!

    Now he and Lizzie are able to reflect on their journey, they are able to say that although lots of things went wrong, they managed to get them corrected. Although they did have the benefit of experience from their previous self build, there were still new problems that this project threw up that had to be dealt with. Overall, Mike says they are pretty happy with the end result, just not necessarily with how they got there.

    Find out more

    Visit the website of Portee Passivhaus

    Follow Portree Passivhaus on Twitter

    Follow Mike Coe on Twitter

    Catch up on previous episodes with Mike Coe

    HPH259 : Constructing the masonry superstructure of Portree Passivhaus

    HPH220 : How to finish a self build when money is tight

    HPH152 : Should you consider the resale potential of your self build

    HPH054 : Building an autonomous house

    Transcript

    Download a transcript of the interview with Mike Coe

    How relevant is mass?

    Es Tressider is a guest on the Building Sustainability Podcast, talking about whether adding mass to a building will make it more energy efficient.

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  • HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    Ben Adam-Smith shares his own experience of living with a mechanical ventilation system. While he’s clocked up a few error messages on the unit and had more problems than most, he explains why he wouldn’t want to go back to natural ventilation.

    MVHR is a key component of low energy buildings

    In case you’re wondering what MVHR is, well, it stands for mechanical ventilation with heat recovery.

    As buildings become increasingly airtight, a good ventilation strategy becomes all the more important.

    But there’s a clever twist: by controlling the ventilation you can recover the heat when you want to (transferring it to the fresh incoming air).

    Hopefully that’s clear, but if not we made a documentary about airtightness a few years ago!

    Since this documentary was made I have moved into my own Passivhaus.

    Error messages are warnings

    I am a big fan of MVHR (pun intended) but that doesn’t mean I’ve had the best relationship with my MVHR unit.

    I’ve had 3 sets of errors on the machine in the two and a half years I’ve had it.

    The first errors might have been in connection with a silencer that was retrofitted a year after we moved in. I suspect the machine was clever enough to notice something had changed. The errors resolved themselves!

    About a year later, an external pressure message cropped up a number of times.

    The fan status readings on fan speed two which should be 200m3/hour are:

    Supply fan – Speed 550rpm, Duty 15%, Flow 93% ( a noticeable drop in air flow)

    Extract fan – Speed 1900rpm, Duty 48%, Flow 0% ( air flow can be detected from the extract air valves when a piece of tissue is held up to them )

    Error messages can be reset

    Interestingly, these errors can be reset while you’re investigating the cause… but they usually return, even if that is weeks later.

    Apparently there was a known issue with the humidity sensors on my particular unit. This was changed and again it was business as usual.

    However, at the beginning of the year a new error cropped up!

    Nobody likes seeing a flashing red light on their control panel because it means something needs fixing (or at least investigating).

    At this particular point we’d been getting night-time temperatures between -2C and -5C, which is the coldest we’ve experienced since we built the house.

    When the temperature warmed up a little I was able to reset the error and everything would return to normal (or until I could get the machine looked at).

    However, that trick didn’t work the next day.

    The machine completely died and I couldn’t get it to come back on. There was also a light burning smell inside the house.

    I had a couple of concerns at this point:

    • How long will it be until I get my machine back up and running?
    • Might I get a build up of mould somewhere in my system if I can’t get it fixed soon?

    Fortunately when it comes to mould, I was quickly reassured by my friends in the know.

    So, now whilst the problem was investigated we had to survive without the machine.

    With no MVHR running, we resorted to opening windows!

    Not that I’d choose to do this experiment but it was quite interesting to see the impact of living in a Passivhaus with no MVHR running.

    Firstly, the house remained nice and warm inside (the insulation has gone nowhere). Perhaps the heat wasn’t as even; I don’t know. But it wasn’t a terrible experience.

    It was however, a right faff to have to open the windows every few hours… not to mention the heat we must have wasted… and the family complaining at having the windows open when it was freezing outside.

    Perhaps the most interesting impact of no MVHR was the instant lingering smells. My wife noticed that each room had its own smell! And it was definitely harder to shift cooking smells.

    Eliminate the simple stuff first

    On a chat with Steve Clarke at Green Building Store trying to diagnose the problem, we double-checked that power was getting to the unit.

    Embarrassingly I hadn’t even checked the trip switches. In fact, we’d managed to cover them up with a shelving unit so that I’d forgotten they were even there!

    With the machine humming to life, I had a massive sense of relief. Whatever the issue is it’s not quite so urgent when the system is at least on.

    The preheater needs to be replaced

    It didn’t take long to diagnose the problem (the burning smell was the preheater working for the last time) but British wisdom of leaving the EU meant the new preheater took several weeks to get here.

    The warranty period on MVHR units is typically 2 years

    For an essential item for Passivhaus dwellers, this does seem short.

    The clock also starts ticking when you buy it.

    Mike Coe, the self-builder behind Portree Passivhaus, bought his unit in advance and subsequent delays have meant it will already be out of warranty.

    My own unit was out of warranty, too, but the manufacturers kindly supplied the new part free of charge.

    I installed my new preheater!

    With Steve Clarke from Green Building Store on the phone, I was expertly talked through what I needed to do.

    Buying through a company with good customer service was a great move.

    We’ll have to wait for more cold weather to check it has done the job.

    ‘MVHR needs to be as reliable as a fridge’

    I was interested to see whether other people had had trouble with their units and so I posted up on social media.

    I don’t believe many Passivhaus owners have actually had problems, which is a good sign. As Fionn Stevenson says ‘good quality assurance is essential’.

    Andy Simmonds, Chief Executive of the AECB, stressed it is such an important piece of kit. The emphasis needs to be on durability, reliability and repairability.

    He likened an MVHR unit to a fridge.

    Having bought a new fridge when I built the house I have noticed that even fridges have got more complicated.

    In the past it’s normally the plastic door seal that has failed before anything else, but on the new more complex models water dispensers get jammed on and ice trays freezer up, and don’t get me started on the plastic water filters!

    I would not go back to ‘natural ventilation’

    Despite the inconvenience of investigating different error messages, my MVHR unit has never stopped! Yes, I was a bit slow to check the trip switches, but if there’s a next time I won’t make the same mistake.

    If the machine is still operating, you haven’t got a big problem

    If your machine is not working at all – i.e no ventilation whatsoever – then I would really be looking for a speedy repair.

    As with anything in life that breaks, it normally takes a little while to fix it.

    So it would be lovely to have the option of a 24-hour repair service in the years to come.

    Transcript

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  • HPH294 : Using a package supplier to deliver an ecological home – with Adrian Reith

    HPH294 : Using a package supplier to deliver an ecological home – with Adrian Reith

    Adrian Reith explains why the joined up design, engineering and quality of a Baufritz home appealed to him.

    Interview with Adrian Reith

    Adrian considers himself to be a creative person and, following a career in advertising, he was inspired to re-train and become a business coach.

    He and his wife Judy live in the centre of Cambridge, where the opportunities to purchase self build plots are few and far between.

    His persistence paid off

    Over the years Adrian has been very active on the Land Registry website, paying a small amount to find out who owns various sites.

    He used to live over the road from this particular plot, which at that time accommodated a number of small garages, not built for modern sized cars.

    Every year, he would write to the owner and ask if they would be willing to sell, and each year he would receive a letter of rejection back. On his sixth year of making the request, they replied that they would be interested in talking to him about it.

    The land was owned by one of the Cambridge colleges, and at that meeting, Adrian emphasised how they had roots in the area, loved Cambridge, and were looking to build a family home. His initial offer of £350,000 was rejected. He immediately increased the offer to £450,000, which was put to the college committee and accepted the following day.

    The plot didn’t have planning permission but Adrian sought advice from a planning officer before making his offer, who thought it had potential to get planning. It was nevertheless a risk to buy what could just have ended up being some very expensive garages!

    Adrian says that he is a creative person and believes in holding onto your dreams, which is something he thinks probably helped in his pursuit of the land. He also thinks he was fortunate that the plot never came onto the open market as he knows of other people who had also been keen to purchase it.

    Planning permission wasn’t a foregone conclusion

    The site has 16 adjoining properties so they were quite concerned at their prospects of getting planning permission.

    Having lived in the vicinity for a number of years already, Adrian and Judy worked hard to communicate with their neighbours about what their plans were. They even managed to have a number of letters of support for their project, which is quite unusual.

    The application went to committee as there were a couple of objections from people who hadn’t engaged with them in the process. The committee were hugely positive, understanding of the eco-credentials, and granted them permission to build.

    The location had access constraints

    The house is hidden from view from the road, which is made up of mostly large, Edwardian villas, and is approached by the side of two mock-tudor style semi-detached houses.

    The site is roughly the size of two double tennis courts, and Adrian thinks that a developer would have put quite a few houses on there. When considering their options they did contemplate building two houses, one to rent out and one to live in, but decided on just a generous four bedroom house for themselves.

    The groundworks were carried out by a separate company, which was particularly challenging, given the narrow access down the lane and a tree in the way! Being a timber-framed house the foundations had to be extremely flat and accurate.

    The Baufritz approach had great appeal

    Adrian and his wife are well connected in the area and were keen to build a home that would enable them to welcome people into it. They wanted it to be ecologically responsible and easy to look after as they move into older age.

    From his previous experience of having architect designed, experimental glass extensions on the backs of big Victorian houses, that weren’t executed all that well or comfortable to live in, he was keen to go for something that wouldn’t be causing them problems later on.

    The Baufritz approach of joining up the issues of design, engineering, materials, function, execution and low maintenance, was something that had appealed to them for quite some time already, after researching them for a previous project which hadn’t gone ahead.

    He also liked their emphasis on it being not just an eco house, but a healthy house, making sure that there’s no PVC, VOCs and glues. The fact they’ve built many of these houses before, with tradesmen working together and not against each other, meant they weren’t dreaming up a house from scratch, hoping it was going to work.

    The design developed during a visit to the Baufritz HQ in Germany

    The first step for Adrian and Judy was to write down lists of all the things they liked or disliked in previous houses, including room dimensions. That formed their brief which the architect gave to Baufritz to cost.

    Once they had planning permission they spent a week in Germany at the Baufritz headquarters, where they were given an office for the duration, and were able to bring their ideas together.

    They were then taken through a series of checklists during the week, covering flooring, bathrooms, toilets, doorknobs, stairs, windows etc. They loved the experience but were glad of the advice of a former customer that they knew, who had suggested doing a reccy some time before where they had time to take stock without any pressure.

    A novel approach for them was that the factory had movable components, where they could wheel sinks, toilets, baths etc around to end up with the actual physical layout they would have in their own house.

    Ultimately, Adrian is pleased with the decisions they made, although, being a perfectionist, he was bound to have some things he wished he had done differently. Having been in the house for five years now, and making the decisions about it seven years ago, times have moved on and he wishes he had opted for an electric car charging point for example. He also says it was difficult to visualise quite where things were going to go inside the house, as to where electrical sockets would need to go, and how many of them would be needed. He thinks this is something he probably underestimated.

    The factory-built approach gives quality of workmanship

    What they liked about the factory build approach, was that the house components are put together in ideal conditions. So for example, a window is sealed into the wall, in ideal conditions, using ideal tools, and not by someone in the rain on a Friday afternoon plugging a gap with some expanding foam!

    Theirs is a timber frame house with walls filled with a wood shaving waste product. There is plasterboard on either side of the walls to keep the insulation in, with a void before another plasterboard layer to run the services in. On the exterior there is another void before the external covering on the outside of the house.

    There were logistical challenges in getting the house components to the site

    Once the foundations had been signed off, they had the go ahead for the house to be built in the factory, and Adrian and Judy were given a date for delivery.

    Adrian negotiated with a local airfield to have a crane stationed there, for lifting the loads off the six, 20 metre trucks, onto a smaller truck to shuttle back and forth to the site. Once at the site, two cranes lifted the pieces of the house over the tree.

    The house is around 26 metres long, and the facade arrived in only four pieces with the triple glazed windows pre-installed. The first wall was swung over on the Tuesday lunchtime, and by the time the sun was going down on the Thursday, the roof was on and the house was watertight.

    The internal works, such as the underfloor heating, screeding, taping, decorating, plumbing, wiring, kitchen and bathroom installation etc, took a further five months to complete. That work was also done by Baufritz, and they actually moved in ahead of the estimated time, and on budget.

    “This is a modern house with soul”

    This was how one of their friends described the finished house, and Adrian believes it does have a human quality about it that speaks to you. He thinks the oak flooring and doors contribute to this, and give it a sense of calm.

    Image copyright Joakim Borén
    Image copyright Joakim Borén

    Something they particularly enjoy is returning to the house after a period of time away and finding that the MVHR keeps the house still smelling fresh.

    Image copyright Joakim Borén

    The house has an upstairs laundry room, with zoned, controllable heating. They hardly use heating anywhere else in the house, except for in this room where the clothes are washed and hung up to dry. The hot, moist air is extracted from the room, with the heat being recycled and the clothes drying quickly.

    The landscaping will give them privacy

    Adrian and Judy spent time with their architect to understand the light and work out which aspects to look out onto. From the office at the top of the house they look over the mature gardens of their neighbours, and downstairs they face across their own garden.

    Image copyright Joakim Borén

    To create privacy for themselves and their neighbours they planted 30 small hornbeam trees, which will create a high level hedge for screening and leave them feeling less exposed than they currently do.

    Image copyright Joakim Borén

    In hindsight, Adrian would have imported a few tonnes of topsoil for the grass, as he wishes he had sought advice on that from a gardener and not a builder!

    Image copyright Joakim Borén
    Image copyright Joakim Borén

    It is at the premium end of housebuilding

    Adrian accepts that it is not a cheap house, and all the convenience does come at a price. However, its central Cambridge location means that it warrants the investment as they would get their money back should they ever wish to sell.

    He very much enjoyed the process of having a menu of options, and tinkering around with their choices to see what impact that would have on the price. One example was they decided during the planning stage to enlarge the hallways and staircase, even though they knew this would have a heavy cost impact with extra roof, foundations, floor, ceiling, wall etc.

    They are happy to share their ideas

    Adrian and Judy have opened their house to hundreds of visitors over the years as part of Cambridge Open Eco Homes.

    “As a creative person, everybody needs their inspiration, everyone needs to steal ideas. That’s the best way, not to come up with your own ideas but to take someone else’s and adapt it. That’s the best thing. So, I’m delighted to show people around and to help them see a vision of how they can do something that they want to do in their own place.”

    Image copyright Joakim Borén

    They recently published “Act 3”

    Building the house in their 50s is evidence of their attitude towards life and, during the lockdown period, Adrian and Judy published a book that links into their work as life coaches.

    They found themselves repeatedly meeting people of a similar age and stage in their lives where they were thinking about their roles and responsibilities to themselves, their families and the world.

    Their book, Act 3: The Art of Growing Older, is designed to be a framework for helping people answer those questions, based around the ideas of looking at your values, what’s important to you, finding purpose, and sorting out your key relationships. It is their belief that starting with those fundamentals will make the rest much easier to work out.

    Find out more

    Visit the website of Act 3

    Find out more about Baufritz

    Transcript

    Download a transcript of the interview with Adrian Reith.

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  • HPH288 : Renovating a 1960s house for comfort and efficiency – with Russel Hayden

    HPH288 : Renovating a 1960s house for comfort and efficiency – with Russel Hayden

    Architect Russel Hayden explains how he sought to renovate a derelict 1960s house to EnerPHit standards.

    Interview with Russel Hayden

    Russel is an architect who, up until four years ago, had spent his whole working life in London. Prompted by a desire to leave London and move closer to family, he and his wife bought a derelict house in Stockport with the intention of it being a project to renovate, before selling it on and moving out of suburbia.

    They bought the house through a sealed bid system

    At the time, Russel and his family were renting out their house in London and lodging with his in-laws in Stockport when the house opposite came on the market. It had been left in a state of abandonment for around ten years after the owner had died and heirs were being sought.

    The house went to sealed bids, and they won it with a bid of 5-10% over the asking price.

    The budget was set by what they thought the house would be worth when complete

    At around the same time they left London, they received an inheritance which enabled them to buy the house in Stockport, with enough left to cover the renovation works. Despite a few little extravagances, they mostly kept things simple, and having the budget set gave them a clear direction and target. They did end up spending a little more than they expected to, but felt they got good value.

    Upon completion, they had the house valued at significantly more than they had expected. And despite thinking this project would be a stepping stone to something else, they love the house and the area, and have no intentions of moving.

    Time pressures meant there was no fixed price with the builder

    As they hadn’t finished all the drawings, they recruited a local builder to get the house stripped back while they were still living in London. Once they moved, Russel was able to take on the project management role, finish the drawings and oversee the procurement of materials.

    Having that experience and understanding now, he does acknowledge a new found respect for builders for the work they put into getting the materials, finding the right price and coordinating their delivery.

    The builder embraced the learning involved

    The builder had been recommended to them, and although he had never done a project like this before, he had a good attitude and a genuine interest in learning about Passivhaus. That’s not to say there weren’t also times where he found it frustrating not being able to carry on with his work in the usual way.

    Russel paid him and his team of two helpers a daily rate, which isn’t something he would necessarily recommend a self-builder do, but he was living opposite with his in-laws and could be on-site every day to keep a close eye on things.

    Passivhaus consultants were employed

    Russel had done the Certified Passivhaus Designer course before leaving London, so understood the principles involved, but knew that he didn’t have the experience to tackle it on his own.

    They engaged Enhabit to help with the Passivhaus consultancy, who set out four options of how far they could take it: getting it to Building Regulations standard, to AECB Silver, to EnerPHit, and to Passivhaus standard.

    With Russel effectively wanting to use it as his business card for his new venture in the north, they felt it was important to do something that was certifiable and within a reasonable cost. Settling on EnerPHit basically then set their brief.

    “On reflection, it was a very helpful device actually because it then made everything very clear about what we had to do. I think that’s one of the beauties of Passivhaus. Although there are infinite ways of achieving it, you do have a very real target.”

    The building was wrapped externally with insulation

    The house needed a new roof, so making the decision to go with that and wrapping the brickwork in external wall insulation, gave them a clear steer of how they were going to develop the project.

    They sought planning permission because the 280mm insulation would increase the house footprint by around half a meter, and with an extra foot of height on the roof ridge line.

    One of the biggest challenges was with the concrete slab floor, and the problem of the cold bridge at the perimeter. Without wanting to spend huge amounts of money on it, they decided to accept there would be a cold bridge there, but put insulation on the retained slab. They mitigated that by dropping 150mm of insulation externally down to the foundation level.

    They kept structural changes to a minimum

    By deciding not to move windows and doors around unless absolutely necessary they were able to keep the costs down. They did need to remove a chimney breast though, as it wouldn’t have worked with Passivhaus.

    Adding the floor insulation meant the floor was raised to the level of the first step on their stairs. On the first floor they removed the ceiling plasterboard to expose the joists and give a sense of a bit more height.

    Copyright The Modern House

    One of the big changes they made was reducing the size of the garage and extending onto the back of it to make a space that is used as a garden room, office, and exercise studio. It has a timber frame construction with a straightforward flat roof, making it a cost-effective addition to the project.

    Russel’s wife Anna is also an architect and she spent a lot of time researching materials for the interior finishes, and finding fittings which weren’t necessarily particularly expensive.

    They chose a parquet flooring for the ground floor and a lighter oak parquet for the upstairs, which together with the full height doors in the rebuilt partitions, gives continuity between the spaces.

    They fell just short of their airtightness target

    One of the biggest challenges on the project was getting the connection to the existing house right, and particularly minimising the thermal bridges where the garage and extension connect.

    Russel thinks the workmanship around that connection was responsible for them just failing to achieve their airtightness target, with a result of just over 1.1 (where 1.0 is required for EnerPHit). By the time they had that final airtest they were past the point of being able to go back and remedy where the problem may have been. This did mean that frustratingly they weren’t able to get the certification they were hoping for.

    The hands-on experience has been invaluable professionally

    Among the things Russel learnt from this project, was about having the right and patient approach with people. This was particularly the case with having employed a builder on a daily rate rather than a contract.

    He also found that being so involved on site and doing the taping himself, meant that he was gaining a much better understanding of things that worked and things that didn’t, which invariably will influence the way he goes back and details buildings.

    “I think what’s been brilliant about the Passivhaus Designer Course is that I’ve realised that for the last thirty-odd years I’ve been detailing and designing buildings not terribly well without a proper understanding of moisture and how buildings work, thermal bridges and things like that.”

    Copyright The Modern House
    Copyright The Modern House

    He is now working on a Passivhaus self build

    They have since bought a 1960s concrete panel bungalow in the Lake District which was won through another sealed bidding process. With the bungalow quality not living up to that of the view, it became quickly apparent that their best option would be to demolish and replace it with a new building. It is currently at the planning stage and they are looking to make it a timber frame construction built to Passivhaus, or ideally Passivhaus Plus, standards. Being in a World Heritage Site they are keeping their fingers crossed!

    Know your limitations and keep things simple

    For anyone thinking of carrying out their own retrofit, Russel says the budget will be key but it can be very difficult to know how far you can go within that. The balance between getting to the level of comfort required without spending a huge amount of money can be a challenge.

    It is easier if a particular standard is the target, but without that you are left with a number of options.

    It is best therefore to understand the difference between what you want to spend and what you need to spend. Spend it carefully and you’ll get what you pay for. By keeping it simple it will be easier to design and build, and you’ll get a lot more for your money.

    Find out more

    Visit the website of HESKETHHAYDEN

    Follow Russel on Twitter

    Transcript

    Download a transcript of the interview with Russel Hayden.

    Please connect with me

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  • HPH287 : A beginner’s guide to retrofit – with Russell Smith

    HPH287 : A beginner’s guide to retrofit – with Russell Smith

    Russell Smith of Parity Projects explains why a whole house plan is the best way forward for tackling a renovation.

    Interview with Russell Smith

    Russell is a chartered civil engineer whose interest in renovation began after a secondment with the charity Forum for the Future. He began to understand the gravity of climate change and learn about the impact of energy and carbon emissions attributed to the housing stock. This led him to tackle his own housing renovation project, around 16 years ago, at a time when most of the talk was about new builds.

    The renovation of his Victorian property managed to get his heating bills down to around £50 per year. He opened his house up to around 3,000 visitors during the three years he worked on it and was honest with them about what he had discovered, how hard it was and how much it cost.

    Russell realised there was a business opportunity in it and started his own company, Parity Projects.

    A ‘whole house retrofit’ is something of a misnomer

    Russell describes retrofit as being the bits and pieces that are retrospectively fitted. A whole house retrofit is actually a deep refurbishment where everything is done at once.

    “Provided you’ve got a game plan right at the start knowing how everything should fit together in the long-term then your retrofits should add up to a whole house refurbishment in the long-term.”

    Too much information can scare off new customers

    Providing full and detailed calculations and drawings at the outset is likely to overwhelm the majority of people, as they wouldn’t be aware that quite so much was needed.

    Instead, Russell starts by using just enough data to help a customer understand the size of the problem and the opportunity of what is possible with the house. By displaying what the priorities are, they can agree on an appropriate package of measures before moving to the next phase. This would involve much deeper analysis and calculations for every element of the building.

    Phasing a renovation over time takes extra consideration

    Russell explains it can be particularly difficult to get all the elements to fit together if they’re not carried out together in one plan.

    “If you’re only installing some of the measures or you’re only tackling some of the things that you would want to do upfront, really you want to make sure that those things don’t have to be undone to do the next things later on.”

    So ideally it makes the most sense to carry it out in one go if possible. It’s the least costly way of doing it, materials can be bought in bulk, it can all be carried out while no one is living there, it doesn’t have to be tidied away completely at the end of each day, and the airtightness layer and ventilation can be considered for the whole building rather than just room by room.

    Russell does acknowledge that this won’t always be possible as people might not have somewhere else to stay or the finances available all at once.

    Ultimately we want to reduce our demand for heat

    The first step therefore is looking at where heat is being lost. Using the example of a three-bedroom semi-detached property, he explains the different areas:

    Solid walls

    The biggest proportion of heat loss will be through the walls, and without a cavity the insulation will need to either go on the outside or the inside of the building. Careful consideration needs to be given into the way the building was designed to behave, and whether there is already moisture in the brickwork that needs to dry out before any work can start. External wall insulation can be relatively straightforward provided it’s designed properly.

    Windows and doors

    This involves heat loss both through the windows and doors themselves, as well as infiltration around the outsides where they have been installed. If they’re not going to be replaced then the gaps around the structures need to be dealt with very well.

    Under-floor

    Russell says typically around 15% of the heat loss can be through the floor so it’s important to address it early on.

    Roof

    The roof makes up a large part of the surface area of the house and there are plenty of elements which make each unique, such as the different type, orientation, and rainfall.

    Ventilation

    Once the building has been made more airtight and insulated, you need to ensure a good level of ventilation so that the air quality for the occupants is of a high standard.

    “Once you’ve got all of those things dealt with in combination, you’ve resulted in a much lower energy demand than you would have done in the first place. And that’s the point to start considering your heating system and how you would put some heat into the building.”

    The Passivhaus standard deals with these elements

    It is important to ensure that you are ventilating and insulating in combination to get to such low levels of heat demand where a heating system can be virtually unnecessary. But while that’s an aim for every property, the restrictions of budget, priorities and logistics will mean that not every building will be able to reach that.

    There needs to be government backing

    Russell believes there needs to be a government campaign to make people understand the potential of their property and where it can get to provided that strong decisions for a whole house plan are made.

    “It’s got to happen. We’ve got no choice. That is going to happen so that when they are planning their shiny new kitchen, the new bedroom or they’re just redecorating, they can incorporate those things into their thinking.”

    There also need to be low-interest finance options to enable people to move forward.

    Quality depends on good communication

    Quality starts with the design, putting the right list of things together and communicating it properly to the contractor.

    “I think people tend to bash contractors in the first instance for poor quality but the bottom line is, if the contractor’s not been told what to do very well then it’s never going to work.”

    Something Russell has been working on for the last seven years with a cooperative he set up called RetrofitWorks, is bringing those disparate parts of the industry together as part of one organisation. The aim is to give everyone tools at their disposal to do the design, communicate with each other and implement the work so that they can all check anything at every step of the way.

    Cosy Homes Oxfordshire is a manifestation of the key partners they have built up in that area. With some central government funding buying into the model they have been able to define the marketing, clearly describe the approach they think their customers want, design their processes as a cooperative, push forward with the advice, the whole house plans, the detailed design and putting a tender process in place so the right contractors are selected and they can make sure their work is done well.

    Charlie Luxton visits a deep retrofit in central Oxford

    Charlie Luxton visits a refurbishment of a listed barn

    Charlie Luxton checks out a retrofit of a semi-detached property

    They have also used their established supply chains with the creation of the Warmer Sussex scheme, and Ecofurb which will be launching in London soon.

    There aren’t enough skilled workers to meet government targets

    Parity Projects have used modelling tools to identify that the current workforce of around 160,000 in the sector would need to be virtually tripled in order to achieve the government’s target of every house in the UK hitting a minimum EPC score of C by 2030.

    Russell sees this time as a massive opportunity to be training people up from other industries for working in managerial roles as well as the labourers. He thinks that all students in the building sector should complete the same one year course before branching out into their specialities. That way there might be more respect and understanding on site.

    Select a team that is willing to learn

    Russell’s advice to a homeowner considering a renovation project would be to contact a local retrofit coordinator. They will be able to give you advice and technical knowledge to put a plan in place for your property.

    He stresses that if you’re going to do your home up you will probably need to accept that some people working on it might need to learn something new, so ensure that you team up with people that have the right attitude, a genuine interest and are keen to help. Even if they don’t necessarily know it, they will learn and find out.

    There are also free resources available on the AECB website in their Knowledgebase section, and from the Centre for Sustainable Energy.

    Find out more

    Visit the website of Parity Projects

    Learn more about RetrofitWorks

    Follow Russell Smith on Twitter

    Check out our previous episodes with Parity Projects, about what to expect from a detailed energy assessment, and how an assessment can inform retrofit measures.

    Parity Projects carry out an energy assessment at Ben’s parents’ house

    Transcript

    Download a transcript of the interview with Russell Smith.

    Please connect with me

    Subscribe, rate and review the podcast in iTunes

    Rate and review the podcast on Stitcher

    Like our Facebook page

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