Grand Designs New Zealand Straw Bale House Finished
Tom Fenton from Veritherm explains how to test the thermal performance of a home, what this data can reveal and how it can then be used.
Interview with Tom Fenton
Tom Fenton began his career working in the family's design consultancy that focused on the envelopes and facades of commercial and industrial buildings. From this unique vantage point they were able to see the pitfalls in the design and construction process that impact on the performance of the building fabric, which led them to develop Veritherm's test of thermal performance.
Thermal performance measurement should be affordable and scalable
In general, the construction industry's understanding of thermal performance has been based on theoretical design assumptions and desktop modelling. Academic approaches to measuring thermal performance are lengthy, costly and complex, and only really used at a research level. Veritherm's aim was to develop a solution that would be simple to use while being affordable and quick enough that it could be implemented at scale into a range of projects.
Heat will find the weakest point
Even in properties with high-performing materials and quality specifications like a Passivhaus, if the build quality or detailing isn't quite right, then it will be sub-standard compared to its design predictions. Heat is like water and will always find the weakest point, which is where the energy will be lost.
A phased testing approach can be beneficial
The assumption is generally that testing would be carried out on completion of a new build home, but Tom says that actually, the retrofit market is accounting for around half of their business. Using a phased approach, an initial test will give a baseline measurement of the existing home and how it is performing. That information can be fed back to the design team to consider the most suitable fabric upgrades for the property, rather than relying on design assumptions. Further testing can then be used at other stages as new elements are introduced, to quantify the difference that eg, replacement windows or external wall insulation have made. A final test can determine whether the project goals have been achieved.
A phased approach can also be useful on a new build, with measurements being taken before linings are installed. Together with further diagnostics, this can help to identify the possibility of any errors in the external envelope and allow them to be rectified before being sealed up.
There are three phases to a Veritherm test
The Veritherm test is carried out overnight and is broken down into three stages.
The first step is to retrieve relevant design information for the property, such as its thermal specification and basic dimensional information, which is entered onto the Veritherm dashboard.
Also in this preparation stage, the equipment is deployed in the property which includes temperature sensors in each of the habitable rooms, along with fans and heaters.
During the measurement stage, the Veritherm platform activates the equipment remotely and a controlled and measured heat load is applied to the property, using the fans to ensure temperatures are rising uniformly throughout. It is heated for the first half of the night before then being left to cool passively for the remainder of the time. All of the heat load and temperature data is sent throughout the night to the cloud-based software platform, which uses its integrated algorithms to generate the results.
On completion of the test the following morning the results are instantly available in a full report. This quantifies the rate of energy loss from a building per degree of temperature difference, expressed in units of watts per kelvin. The report also breaks down the data from the individual temperature loggers to give a better understanding of what is happening, and where, in the building.
A Veritherm test is quite often carried out alongside other diagnostic tools, such as an airtightness test, so that you can understand what losses are attributable to air infiltration through gaps, and what losses are attributable to the fabric.
Thermal imaging can pinpoint problems
Veritherm's test quantifies the rate of heat transfer, giving the average U-value for the building as a whole. However, if the test flags up any areas of concern, further diagnostics such as thermal imaging could be carried out to pinpoint anomalies.
The performance gap can be quantified
The Veritherm report compares the 'measured' data from the test, with the 'designed' data that was entered into the system in the preparation stage. This gives you a quantification of what that difference is between the designed and as-built performance, ie the performance gap. That information can for example be fed back to the architect to help them improve their design processes. If there's a 400% gap in performance it might mean that the self-builder needs to look at considerably improving their envelope, but if it's only 5% then that's not going to make a significant difference on their fuel bills post-completion.
The data that is produced can also be fed back into energy modelling software to communicate to clients what the longer-term impact will be on emissions and heating demand. This is particularly useful when it comes to designing heating systems to be correctly sized for the property. A new build property that doesn't perform to its designed intent, means that the heating system may not be suitable or efficient. And conversely, many existing buildings have heating systems that are oversized in order to compensate for the unknown, which means there are many capital and operational savings to be had by getting it right and installing the correct system based on the particular property's requirements.
Also in the Veritherm report is a thermal efficiency rating, which is where the rate of energy loss is divided by the usable floor area. Using this traffic light style rating means you can compare for example a 5 bedroom house with a 1 bedroom bungalow, and identify where your property sits on that scale.
The 'designed' and 'measured' data almost never tally!
With the experience of carrying out these tests comes the knowledge that there is nearly always a difference between the designed and measured values. In general, new builds will tend to underperform against their designs. Existing buildings that use EPCs or reduced data standard assessment procedure (rdSAP) will pluck thermal values from standardised tables based on the building's construction type and year of construction, to come up with basic thermal specifications for that property. Once measured, these properties will often outperform what was expected of them and the client can actually have a cost-saving on their planned improvement works. With upgrades being rolled out to millions of homes across the UK, Tom says that there is serious value and savings to be had by using a measured approach to retrofit.
The goal is to have thermal performance testing in legislation
Even testing identical properties on a development can throw up variable results and identify pitfalls in the construction process, in much the same way as when air tests were first introduced, showing why it's so important for testing to be carried out.
Tom is keen therefore for thermal performance testing to be included in Part L of the Building Regulations, and with the introduction of the Future Homes Standard which has a requirement for photographic evidence of insulation, he suggests that using a measured approach is actually of far greater value and a better way forward.
Find out more
Visit the website of Veritherm UK
Follow Veritherm on Twitter
Follow Veritherm on Instagram
Find out more about Veritherm's thermal performance test
Transcript
Building Performance Interactive
Ben Adam-Smith is taking part in a new series for Passive House Accelerator which aims to share lessons and best practice from low energy projects across the UK and Ireland. Hugh Whiriskey of Partel has devised the hour long format and is hosting alongside Ben and Mike Jacob of KISS House. The Building Performance Interactive is held monthly and everyone is welcome.
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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.
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.
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.
Passivhaus does not constrain design
Devon Passivhaus has been shortlisted for a number of awards, including the UK Passivhaus Awards, and Nigel believes this validates the design review opinion and shows that Passivhaus buildings can make great architecture.
Find out more
Visit Nigel's website about The Walled Garden
Visit the website of McLean Quinlan
Visit the website of Goulden & Sons
Find out more about the UK Passivhaus Awards
Transcript
Ben reflects on what it's like to live in a Passivhaus
Homebuilding & Renovating invited Ben to write an article on what it's really like to live in a Passivhaus.
This is what he came up with: 5 things to know about living in a Passivhaus.
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Bruce Bell, founder of Facit Homes, explains why digital manufacturing has a lot to offer in the future of house-building.
Interview with Bruce Bell
Bruce Bell's working life has been spent at the intersection between the digital side of construction and architecture. He originally studied industrial design but then went on to work for Norman Foster's architecture practice in London. He then returned to his studies at the Royal College of Art in London and did a masters degree that focused on digital fabrication. He then ran a traditional architecture practice with a couple of friends. However, all the time, he was drawn to the potential of using digital manufacturing for building homes.
In 2008 he set up Facit Homes to develop these ideas.
Diana Woodward's home, built by Facit Homes, featured on Grand Designs back in 2012.
Digital information is used directly to make components and assemblies
Construction is overwhelmingly analogue. And there's very few projects, or relatively few projects, that I would classify as being digital.
Buildings have been designed on computers for years. The big difference here, however, is that the digital information is then used directly to make components, parts or assemblies. So it's that direct translation from the 3D computer model into physical parts by computers or computer controlled machines that is digital fabrication.
This is not to be confused with pre-fabrication, which in some instances can even be carried out by hand.
Digital manufacturing creates jobs that people want to do
The construction industry suffers from a skill shortage where there are not enough people to all the physical work. This is a product of building in a traditional way, but it could be different. Bruce believes that embracing digital manufacturing would move people into different positions and create more jobs for educated and professional people.
There is consistency because they control the whole process
Facit Homes has become a turnkey provider, doing everything from the concept, design, planning, manufacturing, construction, construction management, all the way through to handover to the customer.
This is to get around the fragmented nature of construction.
Bruce reflects on his years of running a small architectural practice where there would be consultants, engineers, M & E, specialists suppliers, a contractor and of course the customer.
Who's really controlling the situation? It could be very much influenced by any one party's interests. So maybe the contractor has issues or maybe the client wants to take control too much, or maybe the architect is trying to push themselves around. It's not a very solid structure.
In manufacturing one company will take responsibility and put their name to the product, even if they don't do everything themselves.
This means there's a single point of contact for the customer and a better experience all round.
Digital manufacturing is more flexible than prefabrication
Digital manufacturing is flexible because it is based on digital tooling rather than physical tooling. Prefabrication generally relies on a physical space and an assembly line.
You might have wall modules being put together, or roof modules or maybe even whole rooms. And they're very reliant on the physical setup that allows you to make it. And that means they're very standardized.
When it comes to housing no two homes (or sites) are the same and therefore the customer is always looking for a bespoke solution.
Digital manufacturing can deliver on these requirements no matter what the conditions.
A suite of core products simplifies the process
Bruce explains that they've worked hard to develop core products within the business. For example, every house will have the same heating system, one of two different foundation systems, the same timber frame chassis, the same roofing detail and the same window system.
This consistency of products throughout each property allows Facit Homes to deliver the projects for a fixed price, on time and fulfil the customer's brief.
Costings are considered much earlier than a traditional project
The first few steps of Facit Homes' customer journey are not too dissimilar to what you might expect working with a traditional architecture practice. There's a site appraisal and a customer appraisal. They will look at the constraints of the site and the customer's brief, and try to marry those things together.
We have some data-sets and tools that allow us to establish costs at a very, very early stage so that we can develop the brief with the customer and we can make sure that the house is the right size, and it's something that they can afford.
Facit Homes only makes money through construction so it's in their interest to get comprehensive costings and make sure the customer can afford the completed home.
3D visualisation is a key tool
A team of architects design the house, taking into consideration the brief and understanding the light, the access, the views, and so on.
Each step of the way, from concept to working out the layouts in more detail, they get reviewed with the customer.
Because we build everything in 3D, naturally as part of our design process, we have a real time rendering application which allows us to walk through with light and shade and sunshine and materials, and understand how the building will look and feel. And that's great for both us, the design team, and obviously also for the customer. So they really understand what it is they're getting.
They take a holistic approach to sustainability
Facit Homes have considered everything from embodied energy to the manufacturing process, transport, as well as the operational energy use of each house.
They are always looking for materials with a low embodied energy. Interestingly Bruce describes one situation where they had to switch away from using a cellulose (plant-based) fibre to a petrochemical product because it was hard to get a consistent standard of installation with the 'blown in' fibre.
However, of the two choices of petrochemical insulations on the table, there was a huge discrepancy in embodied energy.
What the choice came down to for us was between polyurethane insulation and polystyrene insulation. So polystyrene insulation uses only about 5% of the energy that polyurethane insulation uses in its creation. So that really helped inform the choices for all of the products that we use.
The graphite treated polystyrene bead they now use has a much better flow rate and fills volumes better. Plus it has a slightly better thermal performance.
The building envelope is environmentally optimised
The buildings are all super-insulated and score well in terms of airtightness (normally between 1.2 and 2.2 air changes per hour at 50 Pascals).
However, Bruce believes the additional investment to achieve Passivhaus standard levels of airtightness is hard to justify.
To get full Passivhaus certification, you very much have to be designing your home as a Passivhaus from the start. And it really affects the way that the building is orientated and the size of the openings and all sorts of things. And quite frankly our buildings already have enough constraints. They are quite often in urban situations where we're responding to all sorts of different design parameters. So it's just not realistic, I don't think.
They are keeping an eye on battery technology development
They often review their core products to make sure they are still the best choices. So they have installed a few more air source heat pumps recently.
They are also looking at photovoltaic panels again. With feed-in tariffs so low now, a key consideration is always whether that energy will be used. So when home battery technology gets better then it will be a great advance to make use of power that you've generated over a longer period of time.
Connectivity is the big change that is needed
Building information modelling has become a fairly standard tool in the construction industry, but connecting all this information directly to the supply chain is non existent.
Bruce explains how this gap could be filled.
For example, there are window manufacturers components on the internet, and you can go and download them. But they're not built very well, they are inconsistent, they don't really have all the design options. So you have to rebuild it from scratch with all the information, all the parameters that you need. And then we've built systems so that we can exchange data with a window manufacturer… So for the wider industry to adopt these kind of techniques, that gap needs to be filled. Or alternatively, you're going to see companies who are disruptors, like us, who do everything themselves.
Facit Homes is digitally manufacturing on site again
When Facit Homes featured on the Grand Designs programme back in 2012 they demonstrated digital manufacturing on site using their mobile CNC machine. Since then they have been manufacturing in a factory.
However, deeply understanding the pros and cons of each set-up, they are now returning to site.
You can see people or companies who are heavily investing in modular off site construction, which will grow, but it still will only ever end up being maybe 10% of the market at most, and the other 90% of the market who are building things on site. And for me, that's a really exciting area because it's unexplored, you know, nobody's ever really said. What can we do with this? So for me, that's the most interesting bit is traditional construction, how we can change it.
Find out more
Visit the website of Facit Homes
Follow Facit Homes on Twitter
Transcript
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Ben Adam-Smith reflects on the homes he's lived in and what he's learnt from living in them.
I wanted to do something slightly different to mark my 300th podcast. When do you ever get the chance to reflect on where you've lived your life? Well, I am creating that chance for myself now. It's quite an interesting exercise to put all these places into one document.
I'm going to be looking back at the houses, apartments, and buildings where I have spent my time. I'll also be mulling what I've picked up from those places. Obviously there have been quite a few but I'm going to say I must have stayed in these properties for at least a year… to filter out all sorts of short stays.
And this reminds me of an episode we did with Dr Michaela Benson on how our housing needs change through life.
She had known numerous childhood homes whereas I had only one… and my parents are still there!
The grounding of a loved, family home
I grew up in the countryside in East Sussex and, of course, took it all for granted.
We had space inside and out to play. All our needs were met. We were safe, warm and well fed.
But perhaps interestingly – and this may be true of all buildings – it felt most alive the more people that were there. When we had grandparents to stay, when my cousins came over, family parties and so on.
And one of the greatest joys as a parent myself is taking my own children there, which then becomes one of those family occasions.
Little projects were always on the go
One thing I have noticed over the years is my parents' constant desire to make things better. This could be something as simple as creating a new flowerbed in the garden or be as big as an extension (back in the day).
This was on top of the day-to-day maintenance that really starts to eat into your time.
My dad was never afraid of new technology
There's doubt that as you get older it's harder to keep up! Things seem to change even faster. But my dad has not yet been outpaced. He drives an electric car, maintains a WordPress website and stays constantly interested.
I was an adult (in the late 1990s) when they extended for a second time but I got to experience the build, which also incorporated mechanical ventilation with heat recovery and a solar PV array.
And later, when I started House Planning Help, my dad even hired Parity Projects to do an energy assessment of the house and then implemented the suggested measures.
My home is where my hat is
After school I worked abroad in a few grounding jobs… I washed dishes in kitchens (a plongeur as they would say) and did bar work.
I didn't need much… and that's a good thing because accommodation was basic and often cramped. I just enjoyed the snowy Alps or the cool waters of the Mediterranean.
So when I did start a media production degree at Bournemouth University it seemed like comparative luxury.
Looking at where I lived for two of those years it looks pretty grim but I bet my motivation was how much it cost and whether it had the right number of bedrooms!
This was my first experience of cooking for myself (I don't know whether this was prompted by my spell of working in kitchens or just that I liked eating good food) and cooking smells often lingered when I was about.
Everything is a walk or tube away in London
My first proper job was working in sport on the BBC Snooker tour. I always felt a slight fraud working in sport when I had no real interest, but I learnt tonnes about how live TV programmes are put together and met some really talented people.
I based myself in West London during this time in a shoe box room! Yes, the media doesn't pay very well.
Perhaps the biggest takeaway from living here was how much is on your doorstep in London and how easy it is to travel. Although I owned a car I didn't really use it much, preferring to walk or get the tube.
Sampling African living
I've been lucky enough to travel to a number of countries around the world. Most of the time I would stay a few days or weeks and then move on.
But I did spend over a year in one place. It was a remote village on the edge of Lake Malawi.
An Australian called Ben had set up a community project there and when he got ill with malaria and had to leave, he suggested I stay on.
And what an experience it was. I was the lone Mzungu (or white man) for miles around, but the villagers welcomed me.
Bizarrely this was also where I had my first taste of building, doing some work to a bathroom block and fixing a roof.
Buying a house
Back in the UK I got back together with a girlfriend from university… and then things got serious!
Kay and I bought a house together, got married and had kids (albeit over several years).
I remember one of my criteria in looking for a house was to find somewhere quiet and with a 'dead end' road. This proved to be a good move as the community thrived around us. We knew all our neighbours.
It was in this very house that I started the House Planning Help podcast.
Owning a house rather than renting definitely makes you aware of all the maintenance that a house needs.
We had a leak in the extension at the back which we tried to fix but it kept coming back, so eventually we had to replace the whole thing.
Renting again (but while we build)
It's always interesting to see what criteria are important when you decide where to live.
This time it was completely different. We were building our dream home but needed a temporary base in the interim. A big part of this was getting the location right: we wanted to be close to site and our son's nursery.
We didn't have many choices because we needed to make a quick decision but this 1980s semi-detached house ticked the most boxes.
One big plus of this house was the garden. It was small and secure, and we could see the kids playing outside from the kitchen and living room.
On the downside, after a few months of living in the house we discovered mould was developing around window frames and at the back of one cupboard! It would certainly have made an interesting investigation.
House size doesn't impact on happiness
It is fascinating to see that where you live doesn't really impact on your happiness. I'd lived in numerous houses up to this point and enjoyed them all.
Building a home to order
Life is full of adventures… and building own own house was certainly a privilege.
It means a lot to me that the land where we ended up buying had a family connection. My ancestors used to farm this area and one of them even built his own house (which can be seen at the top of the hill).
As I've said before it surprised how much this felt like home as soon as we moved in. I think some of that might be to do with poring over the plans for months and months, and being so involved in its development.
I also hope that it's giving my kids a solid foundation for their own lives, much like my childhood home did for me. And of course, we're all set to welcome the grandparents can come and stay whenever they want to.
I still feel grateful every day.
Transcript
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Guy Hargreaves explains why he wanted to renovate his Victorian terraced house to Passivhaus standard and how this is going to be achieved.
Interview with Guy Hargreaves
Guy Hargreaves is originally from New Zealand, but he met his wife Susan in Australia.
While living in Sydney they bought and renovated a Federation style house in which to bring up the family. When the children were in their early teens, they relocated to Hong Kong with Guy's work. And after 11 years there, they followed their children to the UK (where they had gone to university and settled).
As Susan was doing a masters in Oxford that became the obvious place to set up home and in October 2019 they bought a Victorian terraced house. Initially they planned to live in the house for a couple of years to get a feel for it, but it quickly became clear that it would need a lot of work to make it liveable. So they started planning a renovation straight away.
The building is set over four floors and includes a self-contained basement flat and converted loft.
A visit to the National Self Build and Renovation Centre was a great starting point
While Guy and Susan were able to lean on the experience of their previous renovation, they were keen to upgrade this property to be a high performance home.
After seeing several Passivhaus homes on Grand Designs over the years they had become interested in the concept, but it was a visit the National Self Build and Renovation Centre (NSBRC) that acted as a catalyst for targeting Passivhaus standard. This is also where they met Alan Budden from Eco Design Consultants, who they would later hire as the project's architects.
Having studied mechanical engineering at university, Guy felt that discovering the Passivhaus standard was a bit of a homecoming.
"The Passivhaus concept itself really grabbed my imagination, to be honest, and I was hooked."
Working remotely caused minimal delays
Having gained planning consent (in January 2020) with help from a more 'traditional' architect, Guy realised that they needed a specialist for the Passivhaus refurbishment. So they hired Eco Design Consultants to take over the project.
This coincided with the beginning of the global pandemic and consequently the project was progressed during lockdown.
Despite this challenge Guy believes it made little impact on the project's timeline.
COVID is more likely to impact the build
As the UK battles with a second wave of the of the pandemic, Guy and Susan have had a few sleepless nights.
They imagine that there is a strong possibility that someone connected to the project could get COVID.
However, with a vaccination programme being rolled out and spring approaching, the situation may ease.
They will obviously be careful how they interact with the builders on site.
Preserving the 'period' feel is important
As part of a three terrace development, Guy was keen to keep the heritage feel of the property at the front.
"We don't want to replace Victorian sash windows with anything that doesn't look like the Victorian sash windows that are there now."
The rear of the building is less important because most houses have been extended over the years and they all look different.
Passion is a driver for targeting the Passivhaus
This renovation will be to Passivhaus standard rather than the slightly less stringent retrofit standard, EnerPHit.
Guy is hoping that it's not going to be a much heavier lift.
"It's the passion I have for the Passivhaus certification more than anything. I'm not sure that the internal feel of the property will be much different if it was renovated to EnerPHit certification."
There are different insulation strategies for different elements of the building
The historic brick facade will remain at the front and back, but it will be insulated internally.
At the back of the house the ground floor will be dug out and a new concrete slab will be set on top of insulation.
In the basement, the top of the floor will be taken off and a Diathonite screed will be laid down.
Interestingly, the party walls will not be insulated at all.
The windows need to be replaced
All windows and doors need to be high performance, so these will be upgraded to triple-glazed products.
The whole building will also be 'wrapped' internally for airtightness layer. This layer will come in the form of various materials.
'Futureproofing' the building justifies the cost
Guy admits that there are significant costs attached to a renovation of this quality and performance.
However, he bought at a price that reflected that the property needed a full renovation. Also, part of retrofitting this home is to futureproof it against the impact of climate change and rising energy costs.
On top of that, there is no doubt that the comfort levels of the house will be vastly improved and this too, along with Passivhaus certification, may be reflected in what the property will be worth in future.
Their builder was keen to develop skills
Finding a builder with Passivhaus experience was really hard.
So Guy has hired a firm who have considerable renovation experience but also demonstrated a desire to tackle a project of this nature.
PHPP adds another dimension to the project
In addition to balancing cost, quality and speed, Guy says you must always think about performance.
"You're always trying to balance what you want to do stylistically with what the PHPP model will let you do! So that becomes a fourth dimension. Everything you do has an impact in terms of, will the building perform the way you want it to perform?"
Find out more
Visit the website of Eco Design Consultants
Follow Eco Design Consultants on Twitter
Transcript
National Self Build and Renovation Centre
Guy and Susan started their renovation journey at the UK's only permanent exhibition centre for self-builders and renovators – the National Self Build & Renovation Centre.
Located just outside Swindon it's a one-stop shop for learning about the build process and sourcing potential suppliers.
They also offer a range of courses and workshops. Find out more by visiting their website.
A tour of Carrstone Passivhaus Plus project
Eco Design Consultants were also behind Carrstone Passivhaus.
Check out this video tour for more information about the house and its design.
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Mike Coe has a progress report from Portree Passivhaus, which is now almost watertight. We pick up the story as the groundworks begin and look at some of the challenges as the superstructure has gone up.
Interview with Mike Coe
Mike Coe has been on the podcast a number of times. Our first interview with him was when he completed building the Cropthorne Autonomous House, where we imagined he might stay put for many years. However, with concerns over climate change, he and his partner Lizzie Stoodley decided to move further north to the Isle of Skye in Scotland.
This meant selling the autonomous house, which was not straightforward, and taking on a second project with well known architects Rural Design.
The sloping site was perfect for upside down living
Mike's previous house, the Cropthorne Autonomous House, had bedrooms downstairs, and the living space and kitchen upstairs. Mike prefers this layout and was keen to repeat it.
That's why one of the attractions of the site was its slope. The main entrance could be at the top of the house, taking you directly into the living space.
Rotten Rock provides a perfect base from which to build
Mike explains that whenever anyone builds on Skye they look for 'rotten rock', which is a combination of the normal clay subsoil but with volcanic small rock particles mixed in. This makes a stable foundation that you can build straight onto.
Although they were digging into the hill, the rotten rock is almost solid enough to dispense with a retaining wall (but not quite!).
His first self build guided a lot of decisions
At the autonomous house the heavyweight structure of the building was used as a thermal store, which would build up heat during the summer and slowly give it back over the winter.
Hence Mike wanted to repeat what he knew worked well. Portree Passivhaus is a masonry building with a cavity wall.
This is unusual for Scotland which has a lot of timber frame buildings, that are quick to put up in the inclement weather.
Resilience was another key factor
The building's heavyweight structure will also make it a 'fortress' for whatever weather is to come.
I think it's inevitable that we're going to get more extreme weather. We haven't had that much of it in the UK yet, but there's rarely a week when there isn't some kind of extreme weather event somewhere in the world which makes it into the news.
The building sits on a tray of insulation
Concrete is poured into a tray of insulation to form the lower ground floor slab. The internal concrete block walls then get built onto the edges of that slab, so the internal part of the house is completely isolated.
The cavity wall is 375mm wide and uses TeploTies for low thermal transmissivity.
With a large open plan living area, the building requires a steel structure for extra support.
The first floor is a beam and block floor, and above this there will be a green roof.
We've got a very substantial roof structure in order to take the weight of the soil on which the grass will grow on the roof. But below that, sitting on top of the structural I-beams, there's another layer of insulation.
There is no environmentally benign dwelling
Mike is well informed when it comes to climate change and believes that we, as a world, could be doing so much more to reduce carbon emissions. So why is he building with masonry when more sustainable materials exist?
There's undoubtedly embodied energy in this house. How significant it is in terms of global carbon emissions compared to things that could be very, very easily avoided, I don't know. In use, the house will have a tiny environmental footprint. It's very energy efficient, it doesn't have a heating system, it'll have renewable energy systems as well.
Although it will be a number of years into the future, Mike says the house will pay back its CO2 debt. And for him it's not just about preventing climate change, this is a house that's ready to face the extreme weather events that have been caused by climate change.
When you look to the future it's not going to blow down. And the turf roof is part of the resilience strategy.
Mike gradually took on more responsibility
Having been very hands-on during his first self build, he had wanted to do less this time. However, he's found himself being drawn in!
Due to concerns over finances, he decided to save some money by installing the mechanical ventilation system and doing all the electrics himself.
But knowing the level of detail required on a project like this, he's also monitoring quality.
It's all about during and post construction quality control. And trying to get across the message that the insulation has got to be kept clean and dry – difficult in this climate – as dry as possible and put in neatly without any gaps – I don't know why but it's just proved to be very tough.
So Mike has spent weekends pulling insulation out, cleaning it, putting it back again. He's also taken responsibility for some of the trickier details.
Mike spotted a thermal bridge across the cavity
With an architect and contractor who haven't built a Passivhaus before, Mike's experience has become extremely useful. During construction he noticed that the steel was creating a thermal bridge across the cavity.
The solution was to shorten the steels and put thermal break pads in. Using stainless steel bolts also helped reduce the transmission across the steel.
Delays have had an upside
Mike's contractor has had to start another project for a local hotel and this has meant a reduced workforce on Mike's site.
However, as pensioners, Mike and Lizzie have been able to squirrel away extra cash.
This gives Mike cautious optimism that he could get towards the end of the project… and even hire decorators (something they'd really like to do).
Find out more
Visit the website of Portree Passivhaus
Follow Mike Coe on Twitter
Follow Portree Passivhaus on Twitter
Transcript
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Neil Sutherland explains how using a design, manufacture and delivery company can give you a better quality of construction.
Interview with Neil Sutherland
Neil didn't take a conventional route into architecture. After leaving school at 16 he undertook a technical apprenticeship with an engineering company for a few years. It was only after finishing his apprenticeship and going travelling around Europe that the wonders of Florence turned his head to architecture. He returned to Scotland, completed his degree and promptly set up his own practice, MAKAR, an architect-led, ecological design and build company.
A unique entity focused on the delivery of great places
Neil summarises MAKAR as not being an architectural practice, builder or manufacturer, but a combination of the three.
His first ten years in business were spent working out how best to develop and design buildings, and was disappointed by the options available to him on the delivery side of things.
When he moved to a live on a farm with his family around 16 years ago, he had land available where he was able to develop and grow his business to include the manufacturing. He now has a couple of large workshops and employs close to 50 people.
Their unique offering means they are currently working at capacity producing homes mostly in the Scottish Highlands, but are also looking to mainstream what they do and make it more widely available.
Certainties can be provided to clients
Neil is able to offer certainties to clients, around design, programme, workmanship and cost. With the alternative being to work with a number of consultants and a builder, he says it can be difficult to find a company who are motivated by ecological progressive areas of working who are able to take on an architect's idea and make it work.
"As I've learnt over the years, the intention is the first stage but one has to figure out how to get things delivered. The execution of things is perhaps far more challenging than coming up with bright ideas."
There are three aspects to a successful project outcome
The first is having a thorough understanding of the client's brief. This involves taking time to sit down with them and really understand their needs.
The second aspect is the site analysis. Every site will have constraints and opportunities, but there's always context; things to respond to, things you want to exemplify or even perhaps reduce.
The third element is a flexible delivery approach.
Neil believes as long as none of these three aspects are compromised, as he suggests happens in the standard approach to the design and delivery of housing, the customer will end up with a wonderful outcome.
Scotland has an abundance of quality timber
Scotland's forestry cover has an unusual species mix, dominated by pine, fir, larch and spruce.
Neil's company is looking to develop progressive ways of utilising that timber, from a structural perspective right through to insulation. They use the common characteristics of those species for different applications and avoid using chemical treatments wherever possible.
Spruce and Scots pine for example can be used for the carcassing of a panel type construction, Douglas Fir for large section exposed beams and posts, and larch is used extensively on the external applications of buildings, such as cladding and decking.
"There's enough there to do everything we want to do, to do it without chemical treatments, and to work in anticipation of the circular economy, in anticipation of the idea that timber buildings are uniquely adaptable in the sense that they are repairable and you can change them. You can take them apart and put them back together again."
They work closely with sawmills
In other parts of the world, and particularly in Europe there are many small to medium sized mills, which relate to their local resource and how it's used. In Scotland, many of the small to medium sized mills haven't survived so MAKAR tend to use a few large sawmills along with a small number of smaller ones.
Rather than the usual design approach of designing something and then looking for what you're going to use to build it, in normal situations they would look at the resource available and respond to that, buying the timber directly from the sawmill.
They use a lean process
Lean process improvement is largely used in manufacturing to improve efficiency and reduce waste.
Neil's interpretation is that it's about people; what motivates them to do things carefully, and with a lot of attention to detail, getting things right the first time and really enjoying what they're doing.
"It's when you go about making things, when you connect the theory and practice of things together, you get a third thing that comes out which is a kind of tangible, pragmatic capability which is not held up as important as it is, in actual fact."
And Neil believes it is the people who are making things who are the best people to ask about how to improve the process.
An ecological approach to engaging with the world
MAKAR use the term 'meaningful work' to explain their working methods. It's about their work being respectful to everyone involved, and respectful to things beyond themselves.
"Every time we build a house, we know that it's going to impact on people's lives in a very profound manner. MAKAR exists because we believe that great buildings and places change people's lives."
The aim is for quality, not speed
The main constraint that MAKAR have with building the houses is the transportation. Their standard panel size is around three metres wide so that it can be transported by road relatively easily.
Such off-site construction methods may be more expensive than other alternatives, but they will be better and more consistently made and speed and cost reductions will come about over time.
The pieces of the house are made in sequence: first the floor, wall and roof panels, then the post and beam elements and finally the modular elements which are the parts of the house that have the plumbing, ventilation and electrics in them.
They try and do as much of the servicing within the modules at their workshop as possible as they believe this to have the best outcomes.
"But the future is about having less and less equipment, more and more fabric first, more and more simplicity around buildings really. But use the word optimisations. So, what equipment you do have you have to make sure it is working well and it's optimised."
Find out more
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Transcript
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Chris Magwood, a director at the Endeavour Centre in Canada, explains the importance of embodied carbon and how building with plant-based materials could transform our new homes into carbon sinks.
Interview with Chris Magwood
Chris Magwood has been working in sustainable building for the last 25 years. He's also written several books such as Essential Sustainable Home Design, Essential Prefab Straw Bale Construction and Essential Hempcrete Construction.
For the last 8 years he's been teaching at the Endeavour Centre which is a sustainable building school based in Peterborough, Ontario.
What is embodied carbon?
Embodied carbon is the total carbon emissions associated with materials through initial harvesting of raw materials and through the entire transportation to manufacturing facility and everything that happens in that manufacturing facility. And then transportation to a job site and the associated emissions with actually doing the installation work on the job site.
Carbon dioxide is an expression of all greenhouse gases
As carbon dioxide is not the only greenhouse gas, other emissions are translated into a carbon dioxide equivalent.
Chris says: "The expression that we use in the calculations is CO2-E – so, carbon dioxide equivalent. So, if it's carbon dioxide, one molecule equals one. But if it's methane, one molecule would equal twenty-five or whatever the number happens to be."
Energy isn't necessarily a proxy for carbon
For a long time the term that was being used was embodied energy, but it's important to realise that energy isn't necessarily a proxy for carbon.
So, two factories could use the same amount of energy, but if one is all solar and one is all coal powered, then the emissions profile of the two would be very different.
Even though in embodied energy terms, that number might look the same. So, this is specifically trying to make emissions the focus and not just energy use.
The carbon footprint of building materials vary drastically
While we probably understand that different building materials have different carbon footprints, when Chris crunched the numbers he was surprised by the extremes.
Chris comments: "I was pretty stunned at the results in that some things just had such a huge carbon footprint and I had never really considered that impact being so big before. And then some things were miniscule."
Plant based materials give us the opportunity to turn our buildings into carbon sinks
As plants grow they pull CO2 out of the atmosphere and release oxygen. Effectively they put the carbon into their physical structure.
So if you're building with a material that has atmosphere carbon stored in it – basically any plant material – in terms of the calculations, it's a negative emission. In other words there's a drawdown of carbon rather than an emission.
"Building with a lot more plant material, we could not only reduce that carbon footprint to zero, we could actually take it into the negative numbers and make drawdown buildings that are in their way drawing down climate change rather than contributing to it."
Straw is one of the best materials
Chris compares two plant-based materials as an example of how even a little processing can increase the embodied carbon.
Although Cork requires quite a bit of heat in its manufacture, it still ends up being a net store of carbon.
Straw, however, has almost no emissions in terms of the harvesting and manufacturing. It's also the waste product of an annually renewable crop. And in the case of grain straws, the carbon in the stalks would have just returned back to the atmosphere in fairly short order.
Chris adds: "Even though all of these plants more or less store a similar amount of carbon, the amount of processing energy that's gone into them does change the net profile."
Timber has a more complex picture
It's much harder to attribute carbon storage to timber because the carbon that's in that tree, depending on when the tree was cut, that tree could have gone on drawing down more carbon as a living tree than it does as a stored tree.
And if you only end up using about half the volume of the tree to make a timber product and the rest of the carbon from that tree ends up back in the atmosphere, you haven't net stored any carbon. And if you've released a whole bunch of carbon from the soil of the forest floor, then it may be worse than a draw down. It might actually cause emissions.
We could become more intentional about what our buildings are doing
Chris is not advocating that all buildings need to be entirely plant based, but he does see a massive opportunity to be more intentional.
"If you can weigh up the carbon storing materials with the carbon emitting materials, you can actually plan a building to land on a target that you're aiming for, whether that's carbon neutrality, storage or a slight number of emissions."
Environmental product declarations report the environmental profile of a material
In carrying out this research, Chris used environmental product declarations, an ISO standardised way of reporting on the environmental profile of a material.
This is third party document where the third party goes in and looks at a manufacturer and traces the entire chain of that product and essentially does a calculation to look at its global warming potential from harvesting of the raw materials through the entire manufacturing process.
Chris explains how he used this information: "I'm basically using those numbers to then multiple it out on my own buildings. So, if a particular environmental product declaration says there are two kilograms of CO2-E per kilogram of this material, then I figure out how many kilograms of that material are in my building and then I can multiply that out and do that for all of the materials and then total that up and get a net, whether it's a net emissions or a net storage."
Concrete, glass, foam and steel all have high carbon footprints
Perhaps as one might expect concrete, glass, foam, and steel all have significant carbon footprints associated with them.
Building a Passivhaus will not necessarily have any impact on embodied carbon
If you're building a Passivhaus, then your choice of materials is really important.
"The way a lot of people will achieve Passivhaus standard here in Ontario, Canada, is they'll throw a whole bunch of foam insulation at that building. And when I modelled that, the embodied carbon footprint, the upfront emissions of making that building, don't ever get paid back by the energy reductions. So, if somebody was using that strategy because they thought they were doing something for climate change, they've actually done exactly the opposite.
The carbon profile of the grid varies according to where you live
This goes back to energy not necessarily being a proxy for carbon.
Energy efficiency – in terms of carbon emissions – is only useful if you use dirty energy (with a high carbon content).
"Here in Ontario, we shut down our coal plants a few years ago, and so our electrical grid is relatively carbon free. And so, savings in energy efficiency, especially moderate ones, our code is now pretty good in terms of baseline energy efficiency. Going from that to Passivhaus, while it may have good implications for the owner in terms of lower bills and comfort and all that kind of stuff, from a carbon emissions profile, it's almost meaningless with the difference between a code built house here in Ontario and a Passivhaus in terms of the emissions profile of operating that building, it's negligible because the carbon profile is so clean on the grid."
Find out more
Visit the website of the Endeavour Centre
Visit Chris Magwood's website
Follow the Endeavour Centre on Twitter
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To celebrate our 250th podcast, Ben Adam-Smith picks out ten of his favourite new build homes. These are all homes he has visited and which have impressed him in different ways.
1. Dundon Passivhaus
Architect Graham Bizley and interior designer Emily Bizley have produced a magnificent, modern family home that takes in all of the surrounding countryside.
There are some fantastic spaces in here and the timber theme flows effortlessly from outside to inside. Graham and Emily also did a lot of the work themselves – true craftsmanship – and this tailors the home perfectly to them.
2. Treehouse
While the finished house may look happily aloft, there were plenty of highs and lows for Jon Martin and Noreen Jaafar. They bought this plot without planning permission, even though the local planning authority said it would never get approval. Needless to say they got the green light!
Then there is the technical challenge of building amongst mature trees. They used pile foundations which carefully stepped around the root structure! Oh, and let's not forget that they used no concrete on the build. Even running out of money they pushed on to secure Passivhaus certification. A truly remarkable home.
3. Fran Bradshaw's house
Located on the Norfolk coast this is a labour of love for architect Fran Bradshaw. There are beautiful materials – straw bales, thatch, lime render, clay plaster, timber – which pair up nicely with the home's high performance credentials.
4. The Autonomous House
Mike Coe and Lizzie Stoodley went all out on this project to create an ultra low energy eco-build. The heat demand for this house is a tiny 4kWh per m2 per year. It brings all the services in house, so there's no mains water or mains drainage. Instead rainwater is harvested from the roof and stored in large tanks (recycled orange juice containers) under the house. There are composting toilets, within the thermal envelope. And a PV array supplies the electricity.
Mike and Lizzie, however, did not stay as long as they intended. Driven by how the climate is changing they decided to move further north to the Isle of Skye… and tackle their second self build!
5. The Cut
Self-builders Tara Murphy and Dimitri Daras spent their money wisely here. It's another example of how a house with a simple form doesn't have to be boring. On the contrary it is striking.
Tara also specified a lot of the house with a baby in tow!
6. Ashley Vale
Yes, this is not strictly a self build but community-led housing. It got a place on this list for a few reasons. It's inspired so many other community-driven projects as this was one of the early ones.
They also managed to wrangle the land away from a volume house-builder, which is an incredible feat.
And at the end of it all, one of their key players Jackson Moulding went on to set up Ecomotive, to empower other groups to do exactly the same.
7. Lansdowne Drive
Architect Bernard Tulkens was behind this project. It's a modest house that embraces simplicity. The cross-laminated timber structure is exposed as is the ventilation ducting, but it works a treat.
Throughout the building they have tried to make as much use as they can of recycled, reclaimed and other materials that have low embodied energy.
And from a Passivhaus point of view there were plenty of challenges… three storey Victorian homes completely overshadow them on the south side. Therefore their West-facing glazing has to be carefully controlled with blinds.
8. Hampshire Passivhaus
Architect Ruth Butler perhaps took on a site that others would dismiss. It was a brownfield site that is overlooked by 13 neighbours. So her constraint-led design would need to rise to the challenge.
And it certainly does. A wonderful contemporary home that feels extremely private from the inside.
9. Buckinghamshire Passivhaus
This was one of the UK's first Passivhaus Plus projects. The architect, Jae Cotterell, was also supplying the build system (PH15). It recorded an outstanding airtightness result of 0.07 ach@50Pa.
A large solar PV, beautifully integrated, helps them deal with a lot of their energy needs before the surplus is exported.
10. Chiswick Eco Lodge
Architect Richard Dudzicki delivered this project for client Oliver Smallman. Oliver lived in a Victorian house next door and had built this property to rent out. But, he liked it so much, after renting it out for a couple of years he decided to move in.
This house feels wonderfully at home on this street and the clever design must take the credit.
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Bill Butcher from Green Building Company, the construction division of Green Building Store, explains how they tackled two radical retrofit projects in West Yorkshire. Each took a 'whole house' fabric first approach in order to improve comfort levels and reduce the heating bills.
Having been Passivhaus pioneers in the UK with their Denby Dale project, the building team at Green Building Company has kept honing their approach.
There was Golcar new build project and Stirley Community Farm retrofit. Now we look at two of their radical retrofit projects, Cumberworth and Lower Royd, and how they embrace the same philosophy but still require bespoke solutions.
Cumberworth radical retrofit
Initially this was part barn conversion and part 1990s extension, so there needed to be two different strategies for this project.
The existing property was hard to heat
The owners were spending £3,500 a year on LPG trying to keep this 150m2 property warm but they were still cold!
A whole house 'fabric first' strategy was adopted
In order to make the house more comfortable and reduce heating bills they embarked on a deep retrofit. This embraced the Passivhaus methodology of making the house draught free, increasing the levels of insulation, reducing thermal bridging and introducing mechanical ventilation with heat recovery.
The designs were modelled in the Passive House Planning Package (PHPP).
Insulating internally maintained the natural stone facade
While a lot of retrofits use external wall insulation, there are a few reasons why they didn't. Cumberworth is at the top of the Pennines and it is exposed to a lot of moisture. The natural stone works well in these parts.
Bill continues: "To build in any other way is totally out of character for this region. And that's what the customer wants."
The three moisture risks had to be addressed
The moisture risk depends on the wall build-up. The ex-barn wall had two stone leaves which were filled with rubble! Being a Victorian barn it was also susceptible to rising damp because there was no damp proof course.
In this high exposure region on the Pennines rain driven damp through the porous stone was another risk.
The third moisture risk is interstitial condensation which is the condensation of internal moist air reaching the dew point where it turns to water as it meets a cold wall.
This section of the building was insulated was a product called TecTem, which is vapour open and breathes like the original building would have done.
WUFI was used to model the moisture risks
A German software package called WUFI was used to look at the moisture risks. To increase accuracy it requires a lot of information first.
Bills gives a few examples: "It takes into account where you are, the orientation of the wall – obviously a West wall up here is in more danger than the East wall because most of our rain comes from the West – the rising damp, the type of stone it is, which quarry it's from, the mortar joints and so forth, and then obviously the insulation."
Moisture sensors in the walls help monitor the situation and allow Bill to assess the accuracy of the program. "I might say that all of the buildings are performing fine."
Insulating the extension was simpler
As the 1990s part of the Cumberworth project is a cavity wall construction it should be less susceptible to rain-driven damp. And it's got a damp proof course which should deal with rising damp.
A ground source heat pump is the heat source
For a new build Passivhaus the energy demand would be so low that underfloor heating would not be appropriate. In a retrofit situation it becomes more relevant.
Also the clients had a field in front of the house which they were keen to use for a ground source heat pump.
Bill explains: "Air source and ground source heat pumps work most efficiently at delivering 35C water, hot water if you like, for your central heating system. And that suits underfloor heating more than radiators. That then informs how you do the floor. Because we don't want to be heating up masses of concrete in a floor because of the slow cooling and heating – it doesn't respond. "
So it's only 75mm of heating screed on top of the insulation.
The insulation follows the line of the roof
As with most of Green Building Company's retrofit projects they have gone for a cathedral roof. This means the insulation is within the structural timber roof and that the loft space is inside the thermal envelope.
Bill says: " What we tend to end up doing is having a studwork parallel with our rafters. So we end up with insulation between the rafters, insulation again, and then within the studwork which is between the purlins more insulation. So, we would use more rigid bats between the rafters – a mineral wool in our case – and the studwork, and then just ordinary loft fibreglass insulation between."
MVHR duct runs were down corridors
As this is a low energy retrofit a mechanical ventilation with heat recovery was specified. It goes without saying that these are fairly intrusive, requiring a plant room for the unit and ducting around the house.
While a new build Passivhaus might use posijoists in the intermediate floor, in a retrofit situation you have to come up with other solutions.
Bill explains that they ran the ducting down the corridor because this was an area where a lower ceiling is not so noticeable.
Vaccuum insulated panels were used around some window reveals
Green Building Store had already supplied outward-opening triple glazed windows to this property five years previously and hence they were keen to keep these!
One challenge they faced was in maintaining the continuity of insulation.
Bill explains: "If you do it [insulation] well in ninety percent of your building, for example, the ten percent becomes very vulnerable to condensation and cold bridging. So, the reveals between the very good wall insulation we were doing, in to the window frame, only allowed for a ten millimetre insulation."
To maintain that u-value at this thickness they needed to use vacuum insulated panels, custom made to fit!
Lower Royd radical retrofit
Much like Cumberworth, this project had two different parts. One was a virgin barn and the other was an existing farmhouse that hadn't been touched since the 1960s. So it was ripe for a retrofit.
A connection to mains gas helped inform the project
Despite it's fairly remote location Lower Royd had a mains gas connection.
The clients had envisaged using a ground source heat pump to heat the house, but in terms of economics, their money could be better spent on insulation!
Bill comments: "A ground source heat pump may cost you twenty-grand to get into the building as opposed to gas and the standard boiler – and we're talking about the smallest condensing boiler, off the shelf from your local builder's merchant – costing, installed, fifteen-hundred, two-grand. You're better off with that saving of fifteen-grand, say, to be put into your fabric. The cheapest energy is the energy you save."
And of course this doesn't rule out changing the heating system to an air source or ground source heat pump further down the line.
A spray-on lime based insulation saved flattening the walls
On the Cumberworth project they used a rigid insulation called TecTem. However, they had to invest a lot of time in flattening the walls to be able to apply it properly. So they were keen to consider other alternatives at Lower Royd.
So they trialled a spray-on internal wall insulation from Italy called Diathonite Evolution.
Not only is it airtight, but it is vapour and capillary open to address any moisture issues.
And being a lime product, it naturally inhibits mould growth.
Airtightness is the most important factor for comfort
Having carried out a few deep retrofits, Bill believes that when it comes to energy and comfort, airtightness is the most important factor. Then insulation comes next.
In fact they may experiment with reducing the insulation levels a little on future projects and look at the impact.
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Grand Designs New Zealand Straw Bale House Finished
Source: https://www.houseplanninghelp.com/tag/home-2/
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