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

Download a transcript of the interview with Es Tresidder

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

February 15, 2023 by Lucy Cowell Leave a Comment

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

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

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Follow Mark Siddall on Twitter

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

January 18, 2023 by Ben Leave a Comment

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

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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HPH322 : An EnerPHit standard retrofit of a Victorian mid terrace home – with Guy Hargreaves

November 2, 2022 by Ben Leave a Comment

Homeowner Guy Hargreaves reflects on adapting and expanding his Victorian mid terrace home, retrofitting the whole building to EnerPHit standard.

Interview with Guy Hargreaves

Initially we chatted with Guy Hargreaves (episode 297) about his aspirations for upgrading his period property for energy efficiency, comfort and to future-proof it for a less hospitable climate. He had gone through the design process and gained planning consent to adapt and extend the property, and targeted Passivhaus standard (largely helped by the form or shape of the building) for the project.

In this episode Guy returns after the renovation and reflects on the construction stage as well describing what the house has been like to live in.

Guy has been fantastic in sharing the journey in our membership community, The Hub.

Go behind the scenes of this deep retrofit. Get access to our in-depth video case study in The Hub

Access issues meant a lot of manual labour

The project began in February 2021 with the strip-out but initially everything had to be removed through the front door! As the one-way street was narrow construction waste had to be dealt with immediately, so it was placed into the back of a truck, driven to the builders' yard and sorted there.

Access improved after a ‘win win' arrangement

As time went by, Guy managed to negotiate access through a private car park at the rear (on an adjacent road). In return he offered to resurface the car park at the end of the process, fix the lights and replace the fence.

Before the renovation

Visualisation of the proposed scheme (at the rear)

New foundations were prepared for the extension

At the rear of the property a small lean-to extension was demolished and fresh foundations were dug for the new extension which would be the width of the property. A digger was craned into the garden from the car park to make the excavation work easier.

Tonnes of soil was removed to prepare for the new foundation.

Then the concrete went in, followed by a layer of insulation and a floating concrete slab.

Steels help open up the old house, but were not necessary for the retrofit

A key element of the brief was to open up the space and so a couple of walls on the ground floor had to go. Structural steels spanning the width of the house were added to take the loads from above.

Some steels already existed in the house from previous renovations but these needed to be replaced.

A contingency is always essential on a retrofit

It is impossible to predict everything that may crop up during a retrofit which is why a healthy contingency fund is always required. One ‘nasty' on this project was the condition of the bay.

Although a homeowner's survey was conducted when the property was purchased it did not flag up any issues. However as the building was stripped back cracks around the windows and crumbling brickwork were revealed, and it became clear that a structural engineer would have to take a closer look.

The outcome was that the bay needed to be rebuilt at ground level with some underpinning necessary at basement level.

Insulation and airtightness strategies change around the building

With a mixture of new and old, brick and timber, combined with planning constraints the technical design utilises several difficult wall build-ups. For example, at the front of the property the appearance had to be preserved and so an internal wall insulation strategy was necessary. This breathable build-up has several layers including a diathonite plaster (the airtightness layer), wood fibre board and a lime based plaster.

The ceiling height in the basement was not as generous as the floors above but removing a 75mm screed layer gave them a bit of wiggle room to add 40mm of rigid insulation.

Up in the attic room rigid insulation was used in the roof. And at the back of the house softer wool batts were filled the timber frame.

Larsen truss built on site for rear extension

The new extension is timber frame and uses a twin stud Larsen truss (300mm) to create a decent size cavity for the required insulation. Cutting and erecting it on site is a simple and cost effective route to achieve high performance.

The room at the top of the house was expanded

A previous owner had converted the loft but the sloping ceilings made it slightly awkward space so Guy planned to open it up on the garden side (south side), which also affords the best view in the house.

Original rooflights before dormer room was created

The skylights before the renovation

Guy understood the overheating risk of the dormer room

That whole south side we glazed in a rather aggressive and somewhat controversial scheme that is going to be a work in progress over time because that dormer is the top of the house… The heat in the house tends to rise into the dormer and add to the solar gain.

External blinds will be installed if ever needed

While over-glazing will lead to overheating Guy did not have his eyes closed. Instead he made sure that there was a strong back-up plan. So there were plenty of window ventilation options as well a reverse cycle heat pump, which can be used for cooling. However, if the temperature becomes unbearable then the ultimate solution will be external shading.

Guy stepped in as quality control

Much like Mike Coe's experience in Portree, Guy decided to monitor quality.

He was on site every day checking how the airtightness layer was coming together, highlighting potential weak spots.

Airtightness became a personal challenge

I knew that we would get the insulation right. But I had absolutely no idea that we would get the airtightness right. And the airtightness, it's like a stop go thing. It's like blowing up a balloon. If there's a hole in it you will get found out.

The biggest worry would be areas where the airtightness layer gets hidden by the construction.

Interim airtightness tests highlighted areas that needed attention

Guys likens airtightness to ‘compliance' in the corporate world. He suggests that those in charge of the results should almost be separate from those doing the work.

Pressurising the fabric of the house and using smoke pens to identify leaks was essential to eliminating draughts and improving airtightness.

Airtightness is really about chasing down your problems.

Pausing construction to perfect the airtightness is not realistic

In an ideal world the required airtightness would be achieved before any finishing work was carried out.

With a team of builders on site it becomes increasingly difficult to address small airtightness issues without progressing work elsewhere in the building.

Delays in ordering increased pressure

With supply chain issues the sequencing on this project added another layer of complexity. Lead times could change overnight.

Architects' contract administration a good call

One of the more valuable things we did was to engage with my architect in an administration contract, which included a fortnightly visit on site, and that kept a level of professional focus on what was needed, what was coming up, where the timing was, what was being realistic, etc.

The Passivhaus standard became a step too far

EnerPHit is the retrofit standard for a reason. It is hard to modernise existing buildings and this is why it's a slightly less stringent target.

Although Guy held onto the goal of achieving the Passivhaus standard target of 0.6 air changes per hour (@ 50 Pa) until the ‘grim death' there came a point where he realised it was too much of a stretch.

Work in the basement apartment had been halted to focus on the main house so that Guy and Susan could move back in as soon as possible.

So the first ‘official' airtightness test of the main house was after they had moved back in (March 2022). At this point it became harder to carry out remedial work.

And an airtightness test for the basement was still needed for an overall result (which came a few weeks later).

The final result for the whole house was 0.95 (ACH @ 50 Pa).

Knowing the ‘Hurculean' effort that went in Guy is immensely proud.

That's what the EnerPHit standard is about… recognising the almost exponential effort in getting from 1 ACH to 0.6 ACH (@ 50 Pa) in a property that's already built.

Comfort tops the benefits

Guy laughs about being able to wear shorts and a t-shirt almost all year round!

He also points out how quiet and still the house is.

With an all electric house the bills are likely to be 1/5 of what they were before, but clearly there has been a massive upfront investment.

Solar PV is the only missing element!

In some respects the people I'm feeling most envious about today are those who have 10 kilowatts of solar PV on their roofs.

With an efficient heat pump providing heating and cooling for the house as well as the hot water, Guy has got nearly everything for the resilience and future-proofing he wanted.

However, there were not many good options for a solar installation. The flat roof at the top of the house was the obvious one but it only had a couple of kilowatts potential.

I didn't think that that was worth the trouble, to be honest. But given everything else that we were doing, it was just probably the straw that broke the camel's back.

Good communication and a stable relationship with your builder is vital

Having been through building processes before Guy has been reminded how important it is to have a stable relationship with your builder. The key to this is staying calm and talking through any challenges.

Changing your builder is a vastly complicated process and it's made even more so when you're halfway through a Passivhaus. And you wouldn't find another builder to want to take it on. So having a strong relationship with the builder is super important.

There is an appetite for retrofit in the UK

Guy has already opened the doors of his home to local community groups interested in retrofit.

There is an enormous appetite in Oxford, and I think probably UK wide, for all or some or most or half of the things that we've done to our property.

Find out more

Check out part 1 – our interview with Guy before construction began

Visit the website of Eco Design Consultants

Visit the website of Equus Design and Build

Transcript

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HPH315 : Simplifying the delivery of high performance, sustainable homes – with Mike Jacob

May 11, 2022 by Lucy Cowell Leave a Comment

Mike Jacob explains how Kiss House is using timber component based production to deliver homes to the Passivhaus standard.

Interview with Mike Jacob

Mike Jacob's journey from project manager of quirky conversions and renovations to co-founder and director of Kiss House happened organically, and stemmed from his ongoing desire to do things in a better way. He continued developing his education and qualifications, learning more about sustainable architecture at the Centre for Alternative Technology, and working for a Passivhaus startup.

Kiss House “brought itself into being”

After a decade spent delivering one-off, complex housing projects, Mike and his colleagues felt that there must be an easier way of transferring their lessons learned into a vehicle that could benefit more people, rather than starting from scratch each time. In doing so, they saw the benefit of scaling up a business that had a repeatable housing product, which felt like it had been individually designed, but without the risk, uncertainty, and stress that often goes along with that.

A bespoke house that a colleague had designed for a private client, started to get enquiries because people thought it was a configurable, repeatable house. This kickstarted their thinking that this could be their vehicle for transferring their lessons learned, and began exclusively working on Kiss House.

It was important for their designs to have an identity

The Kiss House design is a contemporary, cuboid, minimal piece of architecture, drawing on their previous experiences and inspired by landmark projects from the 20th century, to offer more of a mass customisation approach to housing. Although the company is still in its relative infancy, as they develop new housing types they intend to stay within a kind of aesthetic language, being contemporary in nature.

The custom build style alleviates many of the risks

In Mike's experience, many of the truly bespoke projects tend to come unstuck and have tensions for a number of reasons. Often this will happen when trying to incorporate high levels of energy efficiency, and can either end up with compromises on the architecture or the performance.

The Kiss approach aims to be a simple, stripped back, clean lines aesthetic, with uncompromising performance. It can be configurable to an extent, but is ideally suited to a custom build market. Moving forward, they will be building a portfolio of individual Kiss houses that all have commonalities, and beyond that they're having conversations with local authorities and developers who are interested in different typologies, all recognisably Kiss, for delivery of housing at scale.

Each house will be built to the Passivhaus standard

Together with developing their system, they have developed the architectural language for that system which enables them to have a much more flexible kit of parts approach to housing typologies that are more site specific. They are also working hard to ensure that each house will be Passivhaus certified.

They will have their own manufacturing facility in the UK

Mike explains that by vertically integrating themselves with their manufacturing partners, they'll be able to de-risk the supply chain wherever they can. They'll be bringing as much in-house to their manufacturing facility as possible, including the manufacture of the triple glazed windows, to become a one-stop shop for their housing product. And by being more in control of their supply chain, they're able to offer a better service to their customers.

“We've tried to come up with something that addresses all of the pain points, or as many of the pain points as we believe are there, so that our customers maybe even enjoy the experience!”

The ambition is to use only UK grown timber

Currently, the only imported material they use is sheet timber, which they use sparingly and are trying to find workarounds for. They are trying to galvanise the domestic supply chain and are looking at ash and beech for things beyond the structure, such as for furniture and flooring.

Working with the Bio Composite Centre at Bangor University for the last couple of years, Kiss House are also looking to bring to market a UK manufactured natural fibre insulation.

The house is partially pre-fabricated off-site

The kit of parts is manufactured at their facility in the south of England, and is made up of two different types of columns, along with cassettes and panels of various shapes and sizes. They are manufactured digitally on a semi-automated basis and to high levels of precision. The components that leave the facility are insulated, and sometimes with internal lining boards and external cladding. These are then transported to site, where they are assembled without the need for a crane or scaffolding. A typical house would take just a few days on site before it's airtight/weathertight, and then a further 4-6 weeks for the fit-out stage.

The first house will be a demo

Mike explains that they're currently manufacturing their first house, which will be a demo house built at the factory. Their first live projects will be delivered on site as soon as they can get them through the planning system, where they've been experiencing horrendous delays.

It has taken plenty of perseverance to keep going against the odds!

Having lost around two years because of things like lockdown and planning delays, it has been a challenging journey to get to where they are today. However, they, and their patient investors, have kept faith and are at an exciting growth stage where they are joining forces with their manufacturing partner to embark on a new round of fundraising.

Find out more

Check out our previous podcast with Mike Jacob: Does Hiring a Project Manager Save Money?

Visit the website of Kiss House

Follow Kiss House on Twitter

Transcript

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HPH313 : What input might an engineer have for a Passivhaus self build? – with Gwilym Still

March 18, 2022 by Lucy Cowell Leave a Comment

Gwilym Still, of Max Fordham engineers, explains how good planning and simplicity can improve a home's performance.

Interview with Gwilym Still

Gwilym Still is Passivhaus Leader and Director at Max Fordham engineers. Sadly Max passed away earlier this year, but Gwilym explains the lasting impact that he has left on the culture of the practice that he founded. They are focused on recruiting staff who are passionate about design, and then teach them about building physics, rather than recruiting people who have been formally trained in building physics or engineering.

Max Fordham celebrating his house winning the RIBA London Sustainability Award 2019

Max Fordham House (photo copyright Tim Crocker)

There are many conversations to be had at the outset

It is rare for a self-builder to bring in an engineer on day one of their project, but if they did they would be having valuable conversations around things like: the architectural shape, massing and form factor, orientation, glazing and shading, construction types and, whether it will be easy to make airtight and well insulated.

Having these discussions early on means that they're not going to get emotionally attached to a particular design, only to discover much later on that it may not be practical to achieve.

The kitchen at Max Fordham House (photo copyright Tim Crocker)

Design choices have trade-offs

Gwilym explains that part of his job is about helping people understand the impact of the choices that they make, and the trade-offs that are involved. An example is, as a rule of thumb, that the form factor multiplied by 100 is roughly the insulation thickness that will be needed to get to Passivhaus levels of heating demand. By understanding that, clients then decide what their priorities are, and whether adding in an extra room or feature is going to be worth the extra spend on insulation everywhere.

Focus on good daylighting instead of over-glazing

People often fall in love with glossy magazine images of heavily glazed houses, without entirely considering the downsides and summer comfort risks.

Gwilym suggests aiming to set window sizes so that they will give you really good daylighting within rooms. Where possible, orientate the rooms so that living rooms are on the south elevation, and bedrooms on the north. Also aim to have the window head height higher rather than lower, as this will help with getting daylight further into the room.

Start with sizing windows for daylight and ventilation, and then check things like solar gain and summer comfort risks after that. You can also consider the G value of the glazing at this point, so how much heat it lets through compared to the solar energy that's coming onto the window, and how much visible light it lets through too.

Ventilation should be an early consideration

While this can often be overlooked and left to work out later, it's actually a good idea to consider the ventilation system as one of the very first things you think about. Things such as: making sure there's space for the ventilation system to go, that it's close to an external wall, that there's sensible ductwork routes, and that people know which rooms they will be supplying fresh air into, and which ones they're going to extract from.

Incorporating these early will achieve the best efficiency from the system, making it easier to commission and operate.

Make early decisions about the energy strategy

This should be to decide how to heat the space up, and how domestic hot water will be provided. For a lot of schemes, this will now be electric based as people look to decarbonise the grid. Particularly for Passivhauses, the calculations they've done show the additional cost of a ground source heat pump doesn't really make sense over the performance that people are getting out of air source heat pumps now.

Air source heat pumps do have their own challenges in Passivhaus houses, particularly as there aren't many low output units. Where the space heating demand is so low, the problem isn't getting enough heat into the building, it's making sure that the heat pump doesn't switch on and off really quickly or really often.

As general principles then, if you'd like a hot water cylinder, that should be fairly close to the things you'd like it to deliver hot water to, such as showers and sinks. And ideally, that's fairly close to the heat pump unit, which is outside. As they have a particular aesthetic, which not everyone is keen on, you can then factor in the consideration about whether you need to integrate it into a design that conceals it as much as possible. The acoustics should also be considered, as although they're generally fairly quiet, it's still worth positioning them possibly nearer to the kitchen or living areas which will be less noise-sensitive than a bedroom.

Thought should also be given to the size of the plant room, to ensure there won't just be enough room for the MVHR unit, but also space around it for changing filters or accessing it for repairs.

Designing bathrooms and en-suites so that they are fairly close to the hot water cylinder means that pipework runs can be minimised, and the hot water will reach them more quickly. Also give thought to the sanitaryware that will be specified, and opt for low-flow options. As Gwilym says, there's no point in having an efficient heat pump to deliver your hot water, that then gets squandered by a jungle deluge showerhead draining it off really quickly!

Early drainage considerations can minimise heat loss

There are elements of drainage systems that you wouldn't normally think of in a construction project that can have an impact on the heat loss from the building, and the heating demand.

With Passivhaus projects, it's quite common to have soil and vent pipes terminated inside the building with an Air Admittance Valve, so it's worth making sure that it's in a place where it can be accessed and maintained in the future.

And then where Building Regulations want the drainage vented to outside, doing that outside the building envelope, or doing it in as few places as are needed is a good way of having a passive system which minimises heat loss.

Aiming for simplicity can give good results

Gwilym says that many of the high-performing homes don't have anything particularly sophisticated in them. They just have a good design, controls that are simple to use and easy for the users of the building to understand.

Some people can be fixed on the idea of having controls that link to their mobile phones, but actually it's worth keeping things simple, particularly with a heat pump system, and not trying to have an overly fancy thermostat that is doing lots of clever control. And the same applies for lighting systems. Choose really good fittings, and then the controls can be nice and simple.

Also, think ahead about choosing energy efficient appliances, IT equipment and access control systems.

Be aware of annual and seasonal energy use

Energy use in a Passivhaus tends to be mostly from domestic hot water, then space heating and plug loads. Improvements in LED technology has lessened the impact of lighting.

As well as the the split between annual energy use, it's also worth being aware of the seasonal variation, where in some ways it's more attractive to save a bit of energy on heating, because that's a lower carbon approach.

Take advantage of the resources available

Try to get an understanding of the principles early on and incoporate them into the design, which Gwilym suggests doing by accessing resources such as those from the Passivhaus Trust. He would also encourage getting involved with the Passivhaus community on Twitter and places like that, where people are friendly and happy to share experiences. It's worth it for getting advice at the right time, rather than regretting it later!

Max Fordham at home (photo copyright Lydia Goldblatt)

Find out more

Visit the website of Max Fordham

Follow Gwilym on Twitter

Visit the Passivhaus Trust website

Cambridge University build student accommodation to Passivhaus standard

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HPH309 : Keeping costs down by embracing simplicity – with Kirk Rushby and Polly Upton

December 1, 2021 by Ben Leave a Comment

Architects Polly Upton and Kirk Rushby explain how they used their expertise to deliver a striking, high performance home for a very reasonable budget.

Interview with Polly Upton and Kirk Rushby

Having worked at top sustainable architecture practice Architype for many years, Kirk Rushby and Polly Upton were well placed to tackle a Passivhaus project, but bided their time for the right opportunity.

Keeping their cost base low gave them a head-start

Buying a house that they could easily afford in their early years at Architype meant that as their salaries increased their costs did not and so they were able to save money each month. Ultimately this put them in a strong position with cash to hand.

They never stopped considering the opportunities

Even though most plots they found were beyond their financial reach they didn't give up, instead considering various opportunities and thinking that maybe in 5 years or so things might slot into place. Thus anything they learn about the process or sites now might help them down the road.

However, this persistence paid off sooner than they imagined.

They were prepared to take on a plot with challenges

After looking at a few sites they came back to one that had been on the market a while. On the edge of a village, it afforded views to the hills beyond… but there were some drawbacks. The key challenge was access, which was via a low tunnel under the railway. This would make bringing materials to site tricky.

Also being down a private road there were numerous potholes and there was going to be some noise from the railway line.

While this might have been putting other people off, Polly and Kirk felt they could address these challenges. For example, just building to Passivhaus standard would have big acoustic advantages inside the house and eliminate most of the noise from the railway line.

Reducing the floor area helped them keep to budget

The site came with outline planning consent which was perfect for them, as architects, because they could design their own house.

With a fixed budget they had to make sure they had enough money for the project and could see it through. This is where their architectural background came into its own. They started with a rough cost per square metre figure and then went into more detail of how they were going to build it and what each of those elements would cost.

When they couldn't afford it, they reduced the house size and started again

“We designed a 160 square metre house and then we realised that we probably couldn't afford that. And then we realised that maybe we didn't even need it. So we shaved about 30 square metres off and didn't really feel like we lost anything.”

This refinement was an ace up their sleeve. They reached a natural point where if they made the house any smaller then it would become difficult to make the space planning work.

‘Upside down' living was an easy choice

Sharing a similar work experience the core decisions were easy. They wanted to have bedrooms on the ground floor and the living space above (where the views would be better). They planned to use timber frame, which was familiar to them and would also be more practical for delivering to site.

It was the smaller decisions like choosing the wall finishes that prompted more discussion!

The house has a ‘warm' roof

Where some people might have a cold loft space, Kirk and Polly opted to keep the top ‘half storey' of the house within the thermal envelope, giving them more usable space. This is where there office is situated and also where you get the best view.

Each window opening was carefully considered

Polly and Kirk wanted a window arrangement where each window was just the opening.

This meant balancing up daylighting, views, solar gains and cross ventilation (through the openings on the east and west) while also trying to avoid complexity.

On the south side they decided to have a couple of larger windows which would not open. This would be cheaper, as well, plus they didn't need these windows for cross ventilation purposes.

With the main view out to the west they came up with a manual shading strategy for their big door involving roller shutters.

Justifying the cladding choice was the main planning hurdle

Getting full planning permission was fairly straightforward. In fact the main discussion with the planner was over the corrugated metal cladding for the walls and roof.

“We had to convince the planner about the detailing and provide some precedents to show it wasn't going to look like a big agricultural, clunky shed and it was going to be quite refined.”

The non-concrete foundation worked well

With the constraints of the site they wanted to avoid the stress of a concrete delivery. So they took advice from Passivhaus specialist Nick Grant and structural engineer Andrew Collinson about using a compacted gravel foundation.

They weren't afraid to pull in favours

Initially Polly and Kirk didn't know their neighbours or have friends in the area but as time went by they felt more comfortable with getting support when they needed it. Whether it was paying the farmer to help with his telehandler or asking the local builders' merchants to receive a timber deliver, it made life easier and kept the costs down.

Polly's brother Matt built the house

Enlisting a family member to be your builder can be fraught with danger, but both Polly and Kirk felt Matt was right for the job. Polly knew he was a hard worker, who plans well, knows the building industry and is cheeky when negotiating with suppliers. His ‘can do' attitude also goes a long way.

This was to be his first full house build although he'd done a large extension before.

There were nightly meetings!

As Matt didn't live nearby he stayed with Polly and Kirk during the week. That meant that there'd be intense discussions about what was going to happen the next day, the next week or the next month.

Polly's dad and a couple of Matt's friends were the only other workers through the project.

Getting services connected took ages

The build took 15 months and during most of this time Matt was without power.

“We started trying to get the ball rolling the summer before we started building. And we didn't get the last telephone line in until we'd already moved in so it took a long, long time.”

Kirk believes the utilities companies don't have the same sense of urgency that you do. Plus there were agreements with third parties to arrange, which all takes time.

Luckily Matt was able to crack on under battery power and using an extension cable from a friendly neighbour. This was yet another advantage of a dry construction method.

Supply chain issues impacted on some decisions

Building through the pandemic there were some big supply chain issues. This meant that they had to think on their feet. Fitting out the interior was subject to what was available at the time so being flexible really helped.

The design of the house helps avoid overheating

The house has been really comfortable through their first summer. Even when it got up to 31C outside, at the top of the house inside it was only 25C. So the design of the house, with its roof overhang and shutters, does the work.

Polly comments: “You learn that at about one o'clock, you need to close the shutters on the big west door.”

The programme is subject to real life

Kirks suggests that amongst the things he'd like to do differently would be to make the programme more straightforward. However, the reality of it is that there are delays with some things and you have to fill the time with other jobs you can do.

Find out more

Visit the website of Architype

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HPH306 : Building an exceptional house beyond the walled garden – with Nigel Dutt

September 28, 2021 by Ben Leave a Comment

Nigel Dutt tells the self build story behind Devon Passivhaus, a Paragraph 55 build.

Interview with Nigel Dutt

Nigel and Eileen Dutt worked in computer software all their lives but maintained a lifelong love of architecture. Upon retiring they moved to Devon and it was always at the back of their minds that one day they would like to build their own home.

About 10 years later it was a piece of land a stone's throw from their house that got them wondering whether it was a potential plot. It had been overgrown with tall leylandii and used as a dumping ground but as it was cleared the site looked more and more promising. The one challenge, however, was going to be getting planning consent.

Buying land without planning permission was risky

At the time, Nigel and Eileen perhaps didn't realise the uphill struggle they were about to face. They knew there had been two failed planning applications but undeterred they bought the site anyway. When they submitted a pre-application to test the waters, the planners took a negative stance and suggested the Paragraph 55 route (then Paragraph 79 and now Paragraph 80) was the way to approach it.

Building in open countryside is normally refused

Development is generally confined to settlement boundaries that exist around villages, towns and cities. Building outside these is virtually impossible. However, there is an exception clause in the National Planning Policy Framework that makes allowances in special circumstances.

Although Nigel's site sits between two other plots and might appear to a laymen as an infill site, the whole parish had been declared as open countryside.

Nigel explains the options under Paragraph 55 (as it was back then):

[The house must be] outstanding architecturally or innovative, raising the standard of design in rural areas, that it reflects the highest standards in architecture, and that it significantly enhances its immediate setting.

Pinterest was a useful tool in shortlisting an architect

Nigel and Eileen have always read architecture websites and noted down particular architects they liked. Nigel comments that the ones they particularly homed in on ‘had almost matching Pinterest boards' of interests to their own and so McLean Quinlan were hired.

The architecture is a response to a historic wall

Although the cleared site was now just a patch of grass, running 70 metres down the length of the plot was a 12-foot high brick wall which had once belonged to the country estate. Two hundred years before the walled garden had played an important role supplying fruit and vegetables to the main house.

This was clearly the anchor point for the whole project and the architects were keen to use red brick for the front facade.

Nigel says: “They didn't want to do a slavish imitation, a pastiche of it. So it was new bricks that matched the old bricks, but the house is altogether neater and sharper looking than a rural, walled garden wall.”

A design review panel considers each project

It's not the planners who decide whether a project fulfils the exception criteria but an independent design review panel.

This means developing the designs when there is no guarantee that the project will ever get the green light.

The design review panel quickly came to a conclusion

After producing a 100-page design and access statement with their architects, they gave a 30-minute presentation to the panel. The good news is that their project was deemed to meet the criteria.

The planners chose to reject the panel's judgement

Amazingly the planners are not obliged to accept the findings of the design review panel.

In this case, the planners still felt that the project did not meet the exception criteria and to build anything would detract from the site… in other words they didn't really want another house.

As they were not forthcoming the next step was to submit a full planning application, although the planners gave advance warning that they would recommend refusal.

The support of a local district councillor made all the difference

It was not quite the end of the story because the local district councillor, who was also a member of the the Development Committee of the local council, requested that they go to committee because he disagreed with the planners too. He was positive about building an eco house and his opinion was that the local district should be proud to have a Paragraph 55 build on its doorstep.

So Nigel got the opportunity to appear in front of the development committee and speak for three minutes. The main point he made was why go to a professional Design Review Panel, if you then pick and choose whether you like what they say.

However, he suspects that one of the main reasons it was approved was because they had their direct neighbours supporting the scheme. They had lived next to this unsightly spot and could see an exemplar house would be a massive improvement.

The committee chairman made the point that they're very used to people making the three minute pitches against applications, but it's very unusual to have third parties come in and support an application.

The scheme now had the go-ahead.

The biodiversity of the site would be dramatically improved

Eileen took control of the planting around the house, which would include 120 trees, 300 metres of hedging and thousands of plants.

And they later got an opportunity to buy part of the walled garden next door (and breathe new life into it).

A key constraint became the height of the house

With the historic wall being such a crucial part to getting a planning consent, they did not want to build above it and that led to it being a single storey building.

Nigel laments the fact that in order to get the space they wanted they had to dig down.

We've got a partial basement, which had never crossed our mind, but to get the square footage that we wanted and also to have somewhere to put the plant room and then with a flat roofed house, somewhere to use as a attic equivalent we went down. And it to some extent spoilt our embodied carbon credentials, because by definition, you're then building a hole, sticking a concrete box in it, etc. So we knew that was a downside and also in cost, but we bit the bullet and did that.

They valued the input of a Passivhaus consultant

Although the architects, builder and supplier of the SIPs system were familiar with Passivhaus principles they hadn't worked on a certified project before so they engaged Passivhaus consultants WARM for input.

This helped identify key areas of the architects' design that might prevent them from achieving Passivhaus standard (in terms of airtightness, thermal bridging, etc). What's particularly interesting here is the architect's concept is largely intact with a few large glazed areas still in the finished design.

The shell of the house was up in two months

The house was built with 4wall advanced SIPs panels which were manufactured in Devon by a company called Tribus.

They were able to complete the entire infrastructure of the house, including floors, windows and roof within two months. This also delivered all the airtightness barriers with the exception of the membrane to seal the roof which had to be done by a specialist.

The house is all electric

Due to their location they have a private borehole and private sewage system. This also means that their only ‘bill' is the electric bill.

However, with solar PV and an air source heat pump they are 40% energy positive.

They generate roughly 10.5MW per year but only use 7.5MW. Overall this means they receive about £1000 per year (which includes a grant for using an air source heat pump).

This is a stark contrast to their old house (which was a similar size) where they were paying £4000 – £5000 for all bills. And of course there's a carbon benefit.

I calculated that it's something like 12,000 kilograms of carbon a year for running the other house. And it's about 300 in this house, and then that, again, is offset by the fact that we contribute to the grid from our solar power, which actually, according to our certifier gives us a negative footprint to the tune of 0.5 ton – 1 ton of carbon dioxide a year.

As you enter the house the tiled courtyard acts as an extension of the garden. Daylight is brought in from above by a four-by-five square metre rooflight.

It's unusual to see a Passivhaus with such a large rooflight, because the gains with this orientation of glass are typically 5 times greater than a window on the south-facing elevation. In practice this means if it's a sunny day the blinds must be closed.

If it's a reasonably sunny day, we close it from the beginning of the day. And we find that isn't a problem because it just means you get a slightly shady interior, which is actually quite relaxing.

Trees will eventually shade the south west elevation

The south west facade also posed an overheating risk. It comprises a wall of glass with no shading! However, Nigel and Eileen did have a plan up their sleeve to retrofit shading should it be a problem. It hasn't actually been an issue, with temperatures rarely getting above 25 degrees. And the long term plan is to use the foliage from several silver birch trees that they've planted to provide summer shading.

The only time we get measured overheating is when we're away and we don't have the option to open the doors and windows. And then we've seen 30 or 32 for a few days in the house. But it doesn't matter to us because we're not there. And we find even coming back with the house like that, we can get it back down within an hour or so to something like 24, 25.

Spending time refining your plans saves money

Having spent a lifetime in software Nigel is well aware that fixing anything in the design stage saves money.

There's a rule of thumb in software that if you fix something in the design stage, it costs x. If you find the problem in the implementation phase, it costs you 10x. And if you find the problem when you ship the product, it costs you 100x. So we knew that taking time over design to look ahead and solve these problems was worth doing.

An airtightness champion is a good idea

If you're tackling a project like this Nigel recommends employing someone to oversee the quality of the work. Russ Hancock from Goulden & Sons, who was the on-site project manager, became a convert to Passivhaus. Not only did he do training with WARM but he was always on site to check the work being done and make sure that everyone on site understood the goals of the project and what could jeopardise its success.

Passivhaus does not constrain design

Devon Passivhaus has been shortlisted for a number of awards, including the UK Passivhaus Awards, and Nigel believes this validates the design review opinion and shows that Passivhaus buildings can make great architecture.

Find out more

Visit Nigel's website about The Walled Garden

Visit the website of McLean Quinlan

Visit the website of Goulden & Sons

Find out more about the UK Passivhaus Awards

Transcript

Ben reflects on what it's like to live in a Passivhaus

Homebuilding & Renovating invited Ben to write an article on what it's really like to live in a Passivhaus.

This is what he came up with: 5 things to know about living in a Passivhaus.

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HPH305 : Building a Passivhaus with cross-laminated timber – with Mick Woolley

September 8, 2021 by Lucy Cowell Leave a Comment

Mick Woolley explains how the use of timber was a key element of his award-winning Passivhaus bungalow.

Interview with Mick Woolley

For the last two years, Mick Woolley has been living in his Larch Corner Passivhaus which was the Small Projects winner in the 2021 UK Passivhaus Awards.

His self build journey began following the loss of his wife. He had long held an interest in self building and took the attitude “what could possibly go wrong!”

To watch the documentary about Larch Corner go to PassivhausSecrets.co.uk

He broadened his search area

Initially beginning his search in the south east of England to be closer to his two sons in Surrey, Mick found a lovely plot, surrounded by a vineyard, and just 30 miles away from them. But despite the proximity, it had taken an hour and a half to get there and was £450,000 before he’d even knocked the existing bungalow down. It was at that point he decided to abandon his search in the south east and opened up to looking at sites as far afield as North Wales and Cornwall.

They made changes to the planning designs

Mick saw a plot on RightMove, that seemed to be in a pleasant village location at the northern tip of the Cotswolds. Close to a National Trust garden and Stratford upon Avon, he felt he would be able to find enough to do in the area and was surprised when he managed to purchase it for around the guide price at auction. It came with planning permission for a single storey Passivhaus with a design that he admits probably didn’t appeal to everyone, and is why he thinks there wasn’t more competition in the bidding.

Although not put off by the design, he was sceptical of its Passivhaus credentials and enlisted Mark Siddall of LEAP to re-work the plans. He did however want to keep it a bungalow to make it accessible for a family member who uses a wheelchair, but also because it future-proofed it for him too.

The original design had a lot of corners so they removed some of these and also had to raise the roof to ensure there was adequate head height for insulation. They swapped the entrance hall and study around to ensure a better flow into the house, and took out the many corner windows from the plans. Mark instead designed an arrangement of windows that came in 2 sizes: smaller ones for the bathrooms and bedrooms, and larger windows with seating elsewhere.

Timber was an important element of the design

Mick wanted to build using Cross-Laminated Timber (CLT), as much for the visual impact it provided inside as for its structural qualities. The bungalow uses 17 sections of spruce timber, which have 6 layers, are edge-glued, and don’t require an airtight membrane around the outside.

The roof came with a cassette of insulation in it so the structure went up in two days, and had an airtight wrap over the top by the end of the third day. The walls are made of an I-frame structure with blown-in wood fibre, giving a thickness of around 600mm and a U-value of 0.1.

The exterior of the bungalow has larch cladding.

The foundations were pre-cut to size

The building has a Jackon XPS foundation which was pre-cut to the required size and slotted together, with an XPS upstand that locked into the perimeter. This created its own formwork for the concrete pour.

The flat roof has a camber of around 5 degrees for shedding water. On top of the insulation is a cold roof section of ply and bitumen that provides the finishing structure on which to put the green roof. Mick says he checks up there from time to time just to check that seedlings for trees and other unwanted plants haven’t blown in and taken root!

He was keen to be hands-on

With Mick being on-site throughout the build process he was keen to get involved in any way he could, so one task that he took on was the airtightness taping. His top tip for getting it into the corners is to ideally bend the tape in two in order to push it in and get good contact right the way through the junction.

The straight lines of the 17 sections of CLT only took an hour to do, but all the other joints around the doors and windows took a lot longer!

Mick employed Alan Clarke as his M&E engineer and he carefully designed the ventilation system so it could go through cupboards and be kept out of the way, but still accessible if needed. The full design with all of the MVHR kit was supplied as a single delivery, and Mick took on the installation of the pipework himself. Not having any experience of doing something like that, he did find it took him a very long time to put together!

There is around 140 square metres of floating floor, which was designed to be laid to flow through without any junction strips at doors. His builder Andy took time to work out the geometry to ensure that boards were centred and wouldn’t end up with slivers at the edges, which Mick was then able to lay.

Always make space for storage!

Although Mick was adamant that he wanted to use CLT, he now realises that he could have been more efficient with materials and created the timber finish that he was looking for by using large sections of three-ply timber.

If he were to do the build again, he would probably opt for a two-storey building, though still keeping a downstairs bedroom. He says that the UK housing stock is generally fairly deficient in terms of providing for the elderly and those with mobility problems, so designing at least one bedroom downstairs is really important.

Mick says that going for a two-storey design would improve the form factor and use a lot less insulation. It is also more efficient in having less foundations and roof.

Lack of storage space is often a real problem in typical new build homes, but Mick is delighted at the amount of space they designed into his home, including a large storage wall. He also has a double garaged sized shed, although this is currently housing lots of off-cuts of CLT and three-ply materials that are waiting to find a home!

He emphasises why it’s always a good idea to build into the loft as that’s also potential space that can be used for storage.

Find out more

To watch the documentary about Larch Corner go to PassivhausSecrets.co.uk

Check out the website of LEAP

Follow Mick Woolley on Twitter

Follow Mark Siddall on Twitter

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Download a transcript of this podcast.

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

March 24, 2021 by Ben Leave a Comment

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.

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