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HPH332 : How accurate are Energy Performance Certificates (EPCs)? – with Tom Gwilliam

HPH332 : How accurate are Energy Performance Certificates (EPCs)? – with Tom Gwilliam

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Tom Gwilliam explains what Energy Performance Certificates (EPCs) are, how they are created and why they are unlikely to be a useful measure of how energy efficient a building is.

Interview with Tom Gwilliam

Tom is a sustainability consultant at Etude, with a background in structural engineering, energy assessment and whole life carbon analysis. This episode was inspired by a previous episode, Should we celebrate architecture that performs poorly?, which relied heavily on EPC data.

EPCs are a legal requirement when selling or renting a home

Energy Performance Certificates give a rating between A and G, and a number between one and 100, of how energy efficient the home is. This is the main output, but there’s also other information about what you might do with the home and how the home is performing at the moment.

A domestic energy assessor carries out a SAP assessment on new-builds, or an on-construction domestic energy assessor carries out a ‘reduced data’ SAP (RdSAP) assessment on an existing building. The two are different, but both rely on entering information into a computer model, which outputs the EPC.

SAP assessments make assumptions about how a building operates

SAP stands for the Standard Assessment Procedure. It measures heat loss, domestic hot water use, energy associated with pumps and fans, and the energy associated with lighting. It also estimates what people might use for appliances (‘unregulated energy’, because it varies by number of occupants and their behaviour).

The assessment makes various assumptions and boils them down to a single number for total energy use in kilowatt hours. On top of that, it superimposes carbon emissions, primary energy, and other metrics used for building regulations compliance.

EPCs also measure the cost of operating the building

The EPC process takes the total energy figure and puts a cost on it for the resident. But the accuracy of that cost all depends on the accuracy of the assumptions made earlier in the calculation.

SAP is used to drive policy decisions

There's an aspiration for every property in the UK to be at least EPC C by 2035. Part of the problem is that studies show the EPC rating doesn’t correlate well with the energy use of a building. You’d expect that moving from A to G would see increased energy use, but there isn’t much change in general.

Even if all homes are a C by 2035, we’re unlikely to see much change in energy use in buildings. We’ll still have high energy homes and it will be too late in 2035. There’s a real incentivisation issue, and no strong grasp of how to improve buildings through the EPC process.

Five different assessors would probably come up with five different EPCs

Another major problem with EPCs is consistency – there is none. The EPC industry is not well-moderated, and assessors are paid quite poorly. Plus, there’s pressure at government level from house builders not to increase the cost of assessments and EPCs.

The process relies on a person to interpret a physical characteristic of a building. People might measure things differently or inaccurately, or even completely wrong. Assessors also have to make a judgment on how old a building is, and how it’s constructed. They don’t have the time or money to investigate what’s actually in the walls, so a lot of their work is guessing and being as quick as they can.

There's proven evidence of getting an EPC for a new-build house, then sending an RdSAP assessor to do an assessment the next day, and the two producing completely different results.

Example of an Energy Performance Certificate

EPCs aren’t really about your home, even though they look like it

An EPC is presented in a way that makes you think that it's about your home, but it isn’t. If you had identical buildings in Cornwall and Durham, and carried out identical assessments, you’d get the same EPC. But we know the space heating demands for buildings in those two locations will be very different. That fundamentally undermines the EPC process.

SAP doesn’t have the ‘as built’ check that Passivhaus does

It's possible to game the system, particularly with new-builds. SAP assessors don't get paid well and they have to take the word of the developer or people on site. Assessors don't have the required understanding of how a building is going to perform in reality. They don't see all the detail, so they have to simplify things and make assumptions.

When you have that disconnect between what’s happening in reality and what the computer model says, there's a big incentive for developers to be unrealistic with what they're saying. By contrast, two people carry out the Passivhaus process. There’s a designer and a certifier, and a peer review process going on all the time. It makes it a better-quality process.

Simply adding a requirement for the SAP assessor to go to site at the end of construction would make a big difference.

Thermal bridging is a particular issue

Thermal bridging is a big source of heat loss in new-build properties. SAP has categories for thermal bridges, but they don’t cover everything. It’s hard to have a 3D understanding of a building when working off plans, so if you’re not on site and seeing where thermal bridges are occurring then they’re not getting picked up at all. There's no way of quality checking that process because nobody is overseeing the SAP assessor.

There are lots of assumptions about heating system performance

The technology behind boilers and, in particular, heat pumps has lots of nuances. SAP doesn’t require the level of detail that influences whether heat pumps perform really efficiently or very poorly. The model doesn’t ask for a lot of information about the system, so it can only make a simplified judgement about how it will perform.

A way to improve it would be to break the system down into more component parts, understand each part better, and reflect that in the calculation with evidence. If we’re going to shift to low carbon buildings, SAP assessments should reflect a need for more information and understanding to incentivise developers as part of the building regulations compliance process.

Some people advocate for adopting Passivhaus

It’s a proven system. With Passivhaus and PHPP, there’s a clear link between designed on-paper performance and in-use performance. It’s a tick box exercise in some ways: being detailed in how you assess the building, understanding what is built on site, and making sure that's reflected in the calculation.

Doing more testing would reduce cost for the whole industry

We need to be able to survey our building stock at a level that gives us a better understanding of the energy performance of buildings, and not accept RdSAP as a minimum requirement. There is testing available, but it’s costly – and the only way to bring the cost down is to do more of it.

You can’t judge a building’s quality by its EPC

There is no information about indoor air quality, or other sustainability metrics. This is another area where Passivhaus excels. A Passivhaus is a good quality building that is pleasant to be in. We can't tell from an EPC how good a building is going to be, so it’s impossible to compare one A-rated building to another A-rated building.

Studies are highlighting the issues with EPCs

Etude carried out a research project looking at EPCs versus metered energy use. And UCL Energy Institute has just published a paper looking at buildings they’ve been monitoring over a long period of time. The conclusions all come back to the issue of assumptions made in the SAP assessment.

In addition, there are formulas within the SAP calculation that have been ‘locked in’ for years and they don’t change. The development of SAP over the last 20 years has been slow and it doesn't reflect modern buildings. People know there's an issue, but there's no process for SAP to be regularly updated. When changes are proposed they have to be consulted on, so it’s all very slow.

The Future Homes Standard is expected to change things

Because people know there are issues, an overhaul of SAP is expected alongside introducing the Future Homes Standard in 2025. If SAP changes, that obviously changes how EPCs are generated. It’s not clear how the government would reconcile the difference between existing EPCs and the future EPC system.

Home buyers can try to get hold of the SAP assessment behind the EPC…

…but it requires a bit of knowledge in order to sense check it.

  • Make sure ventilation systems have been entered correctly.
  • If a default value has been used for thermal bridging, you could try and work out if that's a fair assumption for your kind of building. Maybe ask on forums if it is a suitable way of measuring thermal bridging.
  • You could dig into the heating system and make sure what has been selected is what is actually in the building. Has the assessor selected all the right drop down boxes? Has a weather compensator been installed, for example.
  • Also look at what the assessment assumes for the occupancy of the building, because that drives a lot of energy use. You can see if it's related to how many people are going to live in the building.

If the numbers in the assessment don’t seem right then it's up to you whether you appoint someone else to look at it. PHPP, or an open-source version of SAP, is available so it’s an option to try and do it yourself, if you want to.

You’ll always need a SAP assessment because of building regulations…

…but it’s interesting to do a PHPP calculation as well and compare the two. Etude has worked with local authorities to help them understand how SAP differs from reality.

The local authority can’t mandate PHPP calculations, so Etude helps them to convert the SAP result to a more realistic number that can be measured against a policy target. The SAP inputs are still limited, but Etude can correct for known errors in the assessment.

Getting EPC ratings wrong is a problem for retrofit policy

Something needs to be done with RdSAP to make sure ratings are in line with what is expected for a building. As more homes are retrofitted, assessors will need to understand the age of the building, how it’s constructed, and where retrofit measures have already been put in place, in order to have confidence that improvements being made are actually going to make a material difference.

Find out more

Visit the website of Etude

Check out the UCL Energy Institute's research

Download the Passivhaus Trust's research report on EPCs

Transcript

Transcript of House Planning Help podcast – episode 332 (Tom Gwilliam)

What are the UK Passivhaus Awards?

If this award ceremony is not on your radar then you need to invest some time following the competition and delving into the archive. There have been some outstanding self build and retrofit projects in the hall of fame, so we recommend a lazy Sunday morning checking out the fact-files on the Passivhaus Trust website and watching some of the videos.

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

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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!

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Rate and review the podcast on Stitcher

Like our Facebook page

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

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

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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.

The rear (before work began)

Before the renovation

Visualisation of renovated home

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

Transcript-of-House-Planning-Help-podcast-episode-322-Guy-Hsrgreaves

Passivhaus Open Days

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HPH312 : Building a tiny house with natural materials – with Jeffrey Hart

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Jeffrey Hart, natural builder and host of the Building Sustainability Podcast, explains what he's learnt designing and crafting his own tiny house.

Interview with Jeffrey Hart

From an early age Jeffrey Hart had a love for making things. He recalls visiting a friend's house and using a few tools and some scraps of wood to make toy boats. His teachers also encouraged him and would even open up the school on Saturdays so he could continue his project work. After studying industrial design at university he worked as a graphic designer for a while before taking a break and going abroad.

On his travels he came to a small town in Canada where the inhabitants had built themselves homes from straw bales and incorporated re-used materials. It wasn't long before they got him involved plastering and just like that he was building again.

After 5 years on the road, Jeffrey returned to the UK with his mind set on natural building. A first step was enrolling on The Prince's Foundation Building Craft Apprenticeship which offered practical training and served to introduce him to like-minded people.

Finding affordable land is a challenge for any house build

Jeffrey had been searching for land for a house build for some time but ran into the same old problems.

  • Buying a piece of land without planning permission was a massive gamble.
  • Buying a piece of land with planning permission was costly and meant he would have little money left for the build.

So for many years he lived on a canal boat. This kept his costs down and meant he could stay in London because the cost of rent was pushing him further and further out. It wasn't without hardships though.

“The hard reality of winters when you'd get home and I had a diesel heater as a heat source, you turn that on. And all you could really do was get straight into bed wearing all your clothes, because it will take that long to heat up. And that was just my normal life for a long time.”

Building a tiny house keeps costs down

Having travelled for a number of years and also lived on a boat where you could only stand upright in certain places, the prospect of a bespoke tiny home was attractive.

Jeffrey had all the skills to build it and relished the opportunity to make this a showcase project.

Land was still an issue, but instead of buying a plot he was now looking to park his tiny home somewhere.

A movable home doesn't need planning permission

Tiny homes are built on trailers for one important reason: it sidesteps planning regulations. In other words you don't need to own land because you have a movable house… you just need to find somewhere to park it temporarily.

Jeffrey sent emails to every landowner he knew

Although a lot of Jeffrey's emails were ignored his persistence paid off. By probing his existing network Jeffrey was able to source a great opportunity, a win win situation in fact.

The owner of a 700 year old estate in West Somerset proposed a work exchange for his rent, and this is when Jeffrey knew his tiny house project was all systems go.

Think how you want to live in the house

Jeffrey wanted to be fully immersed in the design and build of his home.

After years on the boat he also had certain pain-points to avoid.

Top of that list was a warm house with better cooking facilities, and the ability to stretch out on the floor for exercise, etc.

Not having designed anything since university he went to basics to figure out his layout.

“I drew out on squared paper the very small footprint of my house. And then I got a little piece of paper that I made the size of a bed, and I got a little piece of paper that I made the size of a desk, and a little piece that looked like a wood stove, and I moved them around.”

So Jeffrey had the frame and structure all designed out, including the size and placement of the mezzanine.

“What I realised quite early on is that I don't have that architect ability to know what is a comfortable space just by seeing it on a floor plan. I knew that I needed to get the design 80% there. And then I needed to get inside and actually feel the space.”

A tiny house starts with the trailer

Most tiny builders start with a trailer that is 2.5m x 6.5m.

The trailer is rated for 3.5 tonnes. You can buy a bigger, bulkier trailer but then you need a bigger, bulkier vehicle to move it.

So the key constraints of a tiny house build come from the trailer – a width constraint, a height constraint and a weight constraint.

The ‘weight budget' impacted on every decision

Using a spreadsheet Jeffrey was able to tally the overall weight of the building.

This in turn added another layer to the decision making.

For example, when it came to insulation it was not just about looking at the different materials and their properties.

“Choosing woodfibre over wool adds 100 kilograms to my weight. And I've tried to explain this when I was talking to people. I'd phone up people for advice and they'd just laugh and go, it's insulation, it's light. Well it's not when you add it all together. And then you've got a maximum limit of 2.9 tonnes. So 100 kilograms is a 29th of my weight budget.”

Jeffrey hit his weight budget simply by making a well insulated, well detailed building.

Therefore his design means key components, such as the kitchen, come apart and can be removed.

Not all tiny homes are healthy or well built

During Jeffrey's research he discovered that a lot of tiny house projects had issues. For example they might use a stud frame infilled with spray foam (that contains all sorts of nasty chemicals) or there might be considerable thermal bridging around the steel base.

This provided extra motivation to make this build a showcase for natural materials and good design.

Tiny house living should be as green as it gets

Reducing the scale of any project is the biggest step you can take towards eco living.

However, Jeffrey points out that a 600kg steel trailer is a big carbon emitter.

There's also the question of how often these houses get moved… but Jeffrey is hoping to stay put for a while at least.

Highly efficient homes embrace building science

Jeffrey was keen to apply everything he had learnt in his career, making this a highly efficient building. Thus he focused on creating a high performance building envelope and including triple glazed windows and a mechanical ventilation system with heat recovery (MVHR). This is certainly not common in the tiny house world.

“I do think it is quite rare to do a full wind tightness, fully taped exterior, a proper, breathable airtightness membrane interior.”

Plant-based materials are used as much as possible

It's a standard timber frame (a box frame that starts above the trailer to avoid cold bridging) with wood fibre bats between the framing. Cork clads the entire exterior.

The flooring is local ash from a saw mill 20 minutes away.

The work surfaces use London Plane timber that had been planked and left unused on the Somerset estate.

Building alone requires a different mindset

Being both client and builder has been one of the biggest challenges of this project. Through choice Jeffrey has done 99% of the work himself. However, he's not used to this and has had to reset his expectations of what can get done in a day, week, month or even year.

Therefore while he's solving problems there's nobody else progressing the build.

“I'm so used to different parts of a build happening at the same time, they all come together and fit into each other. But for me just building, I have to just work on one little thing, move on to the next, and keep going like that.”

The wood stove is a necessary evil… for now

Jeffrey is fully aware that getting heat from combustion is not a great idea both for internal and external air quality. However, an electric heating system that runs off solar was out of his price range.

So he's installed underfloor heating to future-proof his home so that as the cost of solar comes down he can switch across (and it's also available if he ever ends up parking somewhere with an electrical hookup).

Biophilic design led to the cruck frame

In the centre of the house is a round wood timber frame.

Through the Building Sustainability Podcast he's got on to the idea of biophilic design, using natural elements in your building for the health benefits.

“It's excessive and it doesn't particularly hold any real function. It adds some stability to the build. But it's overall just there because I think it's a beautiful thing to live in a space with trees in their most natural form.”

Keep learning and experimenting

Jeffrey set up the podcast for two reasons. Firstly he felt that there weren't many good podcasts about natural building. He also realised that now that he was running sites he was the one teaching others what to do rather than learning himself. Having a podcast allows him to have thought-provoking conversations.

I think some of the best episodes are when I go on a slight tangent and I'm talking to… a great example, I was talking to some people from an organisation called Full Grown, and they grow chairs. They use coppice and grafting techniques to grow chairs, still on the tree. And then after so many years they cut it down, turn it upside down, and it's a chair.

After making this episode he then discovered there was someone in Germany attempting to grow houses!

Find out more

Visit the website of the Building Sustainability Podcast

Follow Jeffrey Hart on Instagram

Follow Jeffrey Hart on Twitter

Download a transcript of this episode

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Rate and review the podcast on Stitcher

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HPH311 : Should we celebrate architecture that performs poorly?

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Richard Hawkes from Hawkes Architecture reviews the Energy Performance Certificates (EPCs) of the RIBA House of the Year longlist and asks why we are showcasing poorly performing architecture.

Interview with Richard Hawkes

Richard Hawkes is the founder of Hawkes Architecture, which has developed a speciality for designing outstanding houses that are built in open countryside. There’s a clause in the National Planning Policy Framework that makes this possible in exceptional circumstances (and Richard has been on the podcast before to explain how it works).

However, in this podcast he's going to be reviewing the EPCs of projects that have featured in the RIBA House of the Year competition.

Measuring performance is an important check

When Richard built his house Crossway he received funding from Cambridge University to monitor various aspects of its performance. The research wanted to explore building physics and lifestyle.

So sensors were placed in various parts of the construction, including on the breather membrane layer, within the insulation and inside the thermal envelope.

The temperature was measured at these various points as well as relative humidity.

In terms of lifestyle, early versions of OWL Monitor and Current Cost Monitor were used to measure wattage and time.

Richard gives an example of finding out how much his iPhone cost to charge over the course of a year. It was just 35 pence! In other words we have very little sense of which appliances are using the most energy.

Building performance evaluation should be commonplace

Some people are measuring apples on one house, some people are measuring pears on another house and somebody else's measuring oranges, and each one of them might say, “Oh my house is doing really well.” But it's difficult to find the data to compare one with another. EPCs are trying to do that, but it's not the best tool ever.

An EPC is a rough guide to how a building performs

An Energy Performance Certificate (EPC) is a document that tries to reflect the energy efficiency of a building on a scale of A-G. Thus an A-rated property should perform the best and have the lowest bills. Although it records many useful aspects of the building, such as insulation values and airtightness, it makes a lot of assumptions in the Standard Energy Procedure calculation (SAP). Therefore it has plenty of critics who conclude it is inaccurate.

It is a legal requirement that all buildings have an EPC and therefore if you build a new house you will need one before Building Control will sign off.

In order to get an EPC, an energy assessment will be carried out by an accredited energy assessor. The certificate will then be valid for 10 years.

You can look up a building's EPC using a government database – England and Wales, Scotland and Northern Ireland.

The Energy Performance Certificate for Crossway

EPCs are calculated differently for older buildings

As there is less information available for older buildings they use a slightly different system called RdSAP or Reduced Data SAP.

Crossway has recently been reassessed with RdSAP

With EPCs introduced in 2007, Richard's self build ‘Crossway' was one of the first houses to need to renew its EPC. Despite having used the original SAP for the first certificate the reassessment had to use RdSAP!

“As I understand it, Reduced Data SAP doesn't have any allowance in it for MVHR. You go what?! What other things did it not have?”

Even the assessor added to the list of failings saying there was no way to account for solar gain and no way to add airtightness results.

***Fortunately since recording this podcast Richard has found out that the SAP accredited body, Stroma, have agreed that Crossway can still be assessed under SAP, but there will need to be a new airtightness test.***

RIBA House of the Year 2021 – longlist data

Celebrated projects often do not perform well

Richard keeps a log of all his practice's projects and he was intrigued to see how their EPCs compared to projects given the top accolades.

So he obtained the EPCs for all the latest RIBA House of the Year projects.

“I know that in these awards there is a requirement to submit details about energy performance, but the fact that the house that won doesn't actually have an up-to-date EPC certificate, doesn't have an EPC certificate that represents the building with that development, I find that problematic.”

Only one of the houses on the longlist of 15 projects was an A-rated house, the Devon Passivhaus by McLean Quinlan.

Richard then extended the research to cover all years of the competition.

In the duration of the competition there have only been two A-rated houses that have won.

Across all the longlisted projects (roughly 250 houses) the average airtightness is 4.1!

“We know how good heat recovery ventilation is at helping to reduce the heat requirement for a building, in maintaining air health and CO₂ levels, relative humidity. But for the average, across all of those buildings built just in the last decade to be that high I think it's really quite shocking.”

Conversely Richard's own practice Hawkes Architecture has 17 projects to date and every single one is an A-rated house. The average SAP score of his projects is 102 compared to the average of the House of the Year projects being just 81.

Better building regulations drives up standards

Richard points out that improving building regulations is one way of changing the status quo.

He also mentions that RIBA even has the 2030 Climate Challenge, which is a much more stringent benchmark.

However, the House of the Year competition demonstrates that RIBA do not consider performance essential.

Architectural excellence ought to have a technical requirement

“It's really important that our buildings are responsible with the way they consume resources. And I don't believe that they are judged in that way, either in what they used in their operational life, in energy terms, or the energy that goes into making them, disposing of them.”

Find out more

Hawkes Architecture

RIBA House of the Year competition

Interview with Nigel Dutt about Devon Passivhaus

Follow Hawkes Architecture on Twitter

Download a transcript of this episode

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Rate and review the podcast on Stitcher

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HPH310 : Important takeaways from an exemplar straw panel Passivhaus

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Juraj Mikurcik, Nick Grant and Mike Whitfield reflect on the award-winning Old Holloway project, which is built with EcoCocon straw panels and is a certified Passivhaus.

This podcast is slightly different to normal because it's been compiled from video footage. The video, which can be seen above, is a 10-minute overview of Old Holloway (or you can watch a 2-minute version here).

Passivhaus specialist Nick Grant and Passivhaus builder Mike Whitfield have both been on the podcast before. Architect Juraj Mikurcik has been a friend of House Planning Help over the years and we were delighted to see his home win at the UK Passivhaus Awards and highly commended at the ASBP Awards.

This podcast explores what makes this house build so special.

The design decisions are easy to read and appreciate

In an era of climate emergency we should all be thinking about limiting our environmental impact and reducing our energy consumption.

Old Holloway (with a floor area of 95m2) was built to a tight £150k budget and achieves so much. Not only is it a highly efficient home, but it's been built with as many plant-based and non processed materials as possible.

Constraints impacted the form of the house

The project faced tough planning challenges to get a building consent, needing design approval from the Duchy of Cornwall estate (who sold Juraj the land) before even submitting an application to the local authority. These constraints led to a single storey building and perhaps the rural aesthetic.

The architectural design of the building

Nick Grant says it's his favourite house for all sorts of reasons. Mike Whitfield feels the atmosphere in it or soul quality is really good.

Sufficiency and affordability informed the scale

When it comes to scale it's about finding the right balance. If you build too big you have redundant space whereas if you build too small then people struggle to go about living their everyday lives.

Juraj compares Old Holloway to the TARDIS, because it looks small from the outside but feels big from the inside. An open cathedral ceiling helps create a great sense of space.

Old Holloway's floor plan

Nick also believes small buildings have an advantage.

“Small buildings can look interesting because the texture and contrast of the materials is enough. When buildings become very big that's not enough. So however characterful the render is or the brick, it still looks big and bland, so you then start articulating the building and adding bits on because you think it looks plain.”

Re-evaluating how much space you need is a smart move… but it's also important to build what you can afford.

Materials matter when building a Passivhaus

If you care about the environment then reducing the embodied energy of the building is essential.

Mike says that some people believe it's either natural materials or energy efficiency.

“You can construct an argument to say that the embodied energy in a Passivhaus isn't that important because you're going to save so much energy over the life of the house.”

This might for example lead you to build with insulated concrete formwork.

Juraj specified a Passivhaus certified straw panel system.

Mike continues.

“Ecococon gives you a really instant, pre-fabricated system that is genuinely low energy.”

The structural concrete slab is also the finished floor

At the base of the house a concrete slab has been used, but this structural slab doubles as the finished floor. It took Juraj an incredible 90 hours to polish it!

An insulated raft is made using the ISOQUICK system
The concrete pour
Juraj spent 90 hours grinding down the slab and polishing it
The structural slab is also the finished floor

This route is cost effective. The only downside is that it's tricky to guarantee a certain finish.

The straw panels are wrapped with an airtightness membrane

Nick's house was built with straw bales and he often dissuades people from bale building because it's hard to get them to perform well.

Juraj stresses that EcoCocon is a timber panel based system, produced in a workshop, that uses compressed straw as the infill insulation. As such it's even a Passivhaus certified component.

To achieve Passivhaus airtightness requirements the building is wrapped with a membrane on the outside. Nick explains that generally having the airtightness layer on the outside is something they try to avoid. Juraj has been careful to specify the right product in order to avoid condensation issues. The membrane has vapour openess and the whole build was modelled in WUFI.

An airtightness membrane with high vapour openness wraps the house externally
Warmcel is pumped into the roof void
Studwork goes up internally
No paints are used internally; the clay plaster is the final finish

Don't be afraid to experiment and seek advice from others

Old Holloway is clad in charred timber. This is something Juraj had been wanting to experiment with for some time. He loves the finished effect it created, even if the process was time-consuming.

Charring the cedar
The finished cedar cladding

Juraj believes the crinkly tin roof is the biggest bargain of the whole project. He calls it a ‘very Australian detail'.

Nick says that it's good to see it used simply.

Woodburners/stoves are not a great fit for Passivhaus

One thing Juraj would do differently is not include a woodburner. Although it can be incorporated in a Passivhaus (and has been here) there are lots of reasons to deter you.

  • There are better ways of providing the background heat.
  • It's old-fashioned thinking (burning anything releases a lot of particulate which is not good for health). People like Passivhaus because of the indoor air quality but having a logburner – no matter how sealed the system is – does release particulate into the room (which appears on the MVHR filters)
  • It is a faff to clean up
  • It takes up space
  • You have to keep children away from it
  • Even though it's sized correctly, it is not the same experience as a roaring open fire in an in-efficient house. Nick comments that on social occasions the fire is always out before he arrives because the house is already warm enough!

Nick, Mike and Juraj all have fires, but now say they wouldn't do it again.

Mike suggests that if somebody is fixated on having a fire, then go for a bioethanol burner. This can give the effect of a fire but doesn't need lots of kit. And if you decide it's a waste of space you can just get rid of it!

Juraj erects a sail for additional shading in extreme heat

Total control over solar gains in summer is a masterstroke

Sensible glazing ratios, a significant roof overhang and a pop-up awning make Juraj's house one which will not overheat.

The Passivhaus process is always looking for the best form factor. Old Holloway is not an exact rectangle because it dips in on one edge. This hasn't been done because the shape looked boring and it needed to be articulated: this provides complete solar shading of the biggest windows in summer and a nice area to sit outside whatever the weather.

Nick comments:

“You go from a box it's more expensive, so then you've got to say is it giving me some value for money, and here I think it really does.”

Find out more

Visit the website of Old Holloway

Visit the website of Mike Whitfield Construction

Visit Nick's website for Elemental Solutions

Follow Juraj Mikurcik on Twitter

Follow on Nick Grant on Twitter

Download a PDF transcript of this episode

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Rate and review the podcast on Stitcher

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

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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

Follow Polly Upton on Twitter

Transcript

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HPH307 : Can you have integrity as a housing developer? – with Mike Webb

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Mike Webb explains why he chose to build to high ecological standards even though he could've made more money by just complying with building regulations.

Interview with Mike Webb

Mike Webb grew up in South East London but had his first taste of construction in Tenbury Wells, where he helped refurbish a 17th century, Grade II listed coaching inn. After selling the hotel he and his wife Audrey started investing in property. Mike has also built his own home and ran his own solar PV company. More recently he took on a major development in Seaton, Devon.

The Victorian house in Seaton Beach

Mike moved quickly when he recognised the opportunity

In 2015 Mike was walking along Seaton Beach promenade when a chance remark from one of his friends alerted him to the potential of a site: “If I win the lottery tonight, I'm going to buy that house.”

The location was impressive with views straight out to sea but the dilapidated Victorian house was squeezed between two bigger buildings. There were also signs of regeneration in the area with the recent arrival of the Jurassic Coast Visitors Centre, a new Tesco and new housing around the corner. Mike bought the property within seven days.

Well established relationships helped him secure finance

After putting together a broad-brush business case for the project which included the value of the plot, the cost of demolition, the cost of the build on a square metre basis and also the best guesses of the values upon selling, Mike approached a long-standing friend and asked to borrow £2.5 million.

“If you've got a friendly banker in your pocket, it's always helpful. But he did say right at the get-go, “Happy to bank roll this one, but don't ask again.” So I knew the terms of engagement from day one.”

As a rule Mike doesn't normally work with friends but he knew that this was the only way to make this project happen.

And his ‘banker' did get all his money back with the profit share… and has even enjoyed some of the accolades that have come to this award-winning building.

‘Maximising the planning potential' freed up money to invest in quality

Mike explains that in property embracing the old adage ‘location, location, location' is essential. Blessed with a seafront plot, the next step was gaining consent.

“We fought hard to get eight individual apartments on there at a relatively cheap cost per plot acquisition basis. So as a consequence, we'd got a little bit in hand. And also I'd got the confidence of a friendly banker with a fairly competitive interest rate for development finance.”

Clifton Emery in Exeter, were commissioned to come up with an iconic building that would get the planning gain. Although the scheme was refused initially with a little tweaking it was approved 9 months later (but this delay came with considerable additional costs).

Keep developing your skillset

At a CPD (Continuing Professional Development) at Coventry University Mike met Emma Osmundsen and learned more about Passivhaus. Her talk about building better struck a chord and had planted the seed for making this a high performance development. Emma later shared some contacts with Mike, notably that of Tomas Gartner, an architect who specialises in Passivhaus and at that time was working with Gale & Snowden Architects.

Quality sells

With a strong sales and marketing background Mike is always considering the objections of potential buyers. Doing everything to the best of his ability stacked the deck strongly in his favour.

“Whilst the location was amazing, we then made it super eco. We made it super safe because for example, we've got smoke vents, misting systems, dry-risers, sprinklers in the building.”

A comprehensive specification helped the tender process

Having gained planning consent, architect Tomas Gartner took over and adapted the scheme from a standard build to a Passivhaus project. With a full bill of quantities and lots of attention to detail tender documents were produced and sent out to five shortlisted builders.

Mike believes the biggest risk of the whole scheme was hiring a contractor that couldn't deliver to the required standard. Classic Builders Southwest were appointed after careful consideration. They weren't the cheapest but Mike had confidence in them having seen some of their other schemes and he had developed a good relationship with their senior management team. They also could deliver the project in the shortest time.

External factors caused some costs to rise

While Mike tried to nail down cost as much as possible, there were certain supply chain issues in light of Brexit and then disruption with COVID.

Upskilling the team came with multiple benefits

Mike says one of the best things they did was take the teams from Classic Builders and Fords of Sidmouth for training at WARM in Plymouth. This had been Tomas' recommendation.

Collaboration and education

Training helped the team understand the goals of the project and how they would need to work on site to deliver them.

Only with buy-in was it possible to achieve these stringent standards.

Tomas also suggested that Mike train as a Passivhaus consultant so that he had a deeper understanding of the job.

Where there's a curve there's a cost!

While the original architects were charged with making the building iconic they were not planning to deliver a Passivhaus. So their initial designs left all sorts of challenges for Tomas and the team.

“In terms of the costs, there was a little bit of a bun fight between ourselves and the QS and the main contractor as to some of the finer points and detailing of this. It took a while to get it done, it slowed the programme down, but I've got to say the execution of the project by Classic (Builders), the way they delivered it with their supply chain, the curves are absolutely immense. If I did it again, I probably wouldn't bother.”

The structure of the building changes as it gets higher

There are various reasons why the building uses more than one construction method.

At the ground the building must be able to withstand flooding. Mike explains that it's effectively been built on a beach in a flood zone and protected by a sea wall.

87 concrete piles (13 metres deep) hold up a concrete ring beam, which is insulated from beneath.

“We start our insulation level well below the finished ground level. We then have a robust concrete box that was poured in situ, and that has external EWI wall insulation on it. We then had a concrete transfer slab that has 20 tons of steel in it and there were about 20 lorries of concrete went into it, but it's 325 mm thick, and it oversails the footprint of the building. So you can imagine the structural engineering challenges to get that to support the remaining building cantilevered above the concrete box beneath.”

At this point construction switches to Porotherm clay blocks which are wet plastered on the inside with a parge coat to give you good airtightness detail and rendered on the outside so is a very simple rainscreen cladding.

Each of the Porotherm floors then support concrete planks that are then suspended off the central spine wall which is again built from a Porotherm block but it's a solid core, one that's filled with concrete to give us some thermal mass within the building.

Structural thermal breaks have been used for the balcony

Finally ‘a timber frame bungalow' is perched on the top, which is the penthouse. This was clad in zinc.

A Bauder EPDM roof went on the very top… with one of Mike's most complex solar PV installations.

The view looking down at the roof from a drone

Have faith in putting the environment first

Mike concedes that he could have made more money by lowering standards but that's just not how he wants to operate.

“We're not all about the bottom line, we're all about the quality and the ongoing benefits that that building will give for its lifetime. So yes, we do sacrifice profit for the environment, which is a bold statement for a small company. Me and my wife have a modest existence. We're not particularly flash rich people, we don't need to be. We enjoy doing what we do. And as long as we cannot lose money on it, it would be nice to do another one and another one and another one.

Mike is proud of what he's achieved

Pride is perhaps the most interesting measure of this project.

Mike reflects on the factors that have contributed to these properties selling well and for good money.

“Would we have sold the whole of the apartments for over £500,000 without the curves? Because of location, probably yes. Would we have sold them for over that sort of figure without the Passivhaus certification? Probably yes. But these are always going to be the known unknowns in this journey of ours. I think looking back on it, it's a building that me and my team can be suitably proud of delivering. And the curves certainly do set it apart from anything else on the seafront.”

Seaton Beach is the first multi-block certified to Passivhaus Plus standard in the UK.

Find out more

Visit the website of Seaton Beach Developments

Visit the website of Classic Builders

Visit the website of Fords South West

Visit the website of Norrsken

Follow Mike Webb on Twitter

Transcript

Download a transcript of this episode

International Passivhaus Open Days

One of the best ways to understand what a Passivhaus is by visiting one. Fortunately the International Passive House Association organises Open Days twice a year, once to understand summer comfort and then again to see how Passivhaus comes into its own in winter.

Find out who is taking part.

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

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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.

Copyright Jim Stephenson

Without an external blind the 20m2 rooflight wouldn't be viable

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.

Copyright Jim Stephenson
Copyright Jim Stephenson

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

HPH306-Nigel-DuttDownload a PDF transcript of this episode

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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Finding Land

If you want to build a house then the first thing you need to do is find land. Suitable parcels might be few and far between. And when you do find one, you could face fierce competition. Not only from other self builders, but also developers with deep pockets and bags of knowhow. Our free course will lead you through how you find your dream plot.

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ECO DESIGN 101

So your heart is set on building an eco home but you don’t know where to start. Well, that’s why we’ve developed a 10-part e-course to help you understand some of the important decisions you are going to have to make. Can you have a comfortable, healthy home with low running costs . . . that’s also good for the planet?

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