The Sigma, a near-zero carbon house by the Stewart Milne Group

Beyond Zero's Scott Bilby and Matthew Wright talk Zero Carbon Housing UK with the Stewart Milne Group's director of Business Development, Stewart Dalgarno about the UK's inevitable shift to zero carbon autonomous housing and about the company's Sigma I and Sigma II, 5 star, near zero carbon house.

Stewart Dalgarno podcast

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Scott Bilby: This morning on Beyond Zero we're speaking with Stewart Dalgarno. He's the business development director of the Stewart Milne Group, and they're based in Aberdeen, Scotland. They're one of the UK's largest independent house builders, delivering construction and commercial development projects, social housing, as well as designing, developing and building the UK's first five-star, near carbon zero home called the Sigma Home. It's an eco-house, and it's the Sigma Home that we'll be talking with Stewart about this morning.

So, hello Stewart, and thanks for joining us live from Scotland.

Stewart Dalgarno: Hi guys, how are you doing today?

Matthew Wright: Great. It would be late in the evening there, wouldn’t it?

Stewart: Yes, it's 25 to midnight, but I'm staying up especially to speak to you guys.

Matthew: Great, thanks for staying up for our audience today.

Scott: Can I just say quickly, next week coincidently our guest is Iain Todd and he's from the Aberdeen Renewable Energy Group, so two Aberdeen interviews in two weeks. Well done.

Stewart: It's the centre of the universe at the moment perhaps.

Scott: There's an alignment of the planets or something. Stewart, we know that it's extremely important to reduce greenhouse gas emissions and obviously the housing and construction sector is one of those areas. And the UK's 21 million homes are responsible for 27% of the UK's CO2 emissions, so it's very important that we talk to you about the Sigma Home today.

Matthew: But before we start there, could we find out a bit about how you got involved in this?

Stewart: Yes, the project was started back in November 2006, and there is new legislation coming through in the British government that's going to regulate carbon emissions and energy consumption of domestic housing, and we saw this as either a threat to our business or an opportunity. It's quite onerous in terms of where the legislation is going, and they want all UK houses to be zero carbon by 2016, and they've implemented some new legislation that maps out a direction to achieve that.

We took up the gauntlet, so to speak, to consider how do you do it and can you commercially deliver that solution at a mass level? So, really the history starts from the driver being the government's commitment to reduce its carbon emissions through this new legislation and our desire to build a prototype home and to have it fully tested following this construction process, and to see if we can commercialise that product and bring it to market at a mass level for the UK housing market.

Matthew: So, you were just an ordinary guy who's been involved in the project and reacted to the impending government regulation, or you had a particular interest in sustainable housing before?

Stewart: The company I worked for, Stewart Milne Group, were a house builder, timber frame manufacturer, and a construction company. So, we build 1,200 houses ourself for our own customers, and we supply 8,500 houses to other developers in the UK. So, really I'm part of the product development team at Stewart Milne and I head up that R&D function, and key to this is really the effect it's going to have on our business and the opportunities it might create for our business moving forward.

So whilst, yes, we do believe in climate change and we all need to address that, really it's a commercially driven project to see how we can bring it about for mainstream housing, which typically a lot of these sort of very low energy, low carbon houses are more of a self-build, one-off nature.

Scott: Stewart, can you introduce us then to the Sigma Home and it's a pretty ambitious project you've got happening there. Can you just introduce us to it and give us just a little bit of a background?

Stewart: Yes, the Sigma Home is the UK's first of what we call a code level five. There are six levels in the code which define sustainability and environmental performance for new housing moving forward. It's 100% reduction in CO2 emissions from domestic hot water, space heating and lighting and it's got 80 litres per person per day, which is broadly half the water consumption you would normally expect in a house.

Really the design of the house... it's actually a pair of houses, a semi-detached, four-storey house designed for inner-city, high-density urban sort of living, and to achieve the performance we went for a very insulated, airtight building envelope using timber frame construction. We also made a lot of that in the factory. We actually produce houses in a factory, so we assemble all the components in the factory and then we connect them together on site, so to speak.

In addition to that we've also got three micro-renewable solutions; solar thermal for hot water and under-floor heating system, we've got photovoltaic panels and we've got wind turbines on the house generating electricity to offset the carbon we can't offset through just the fabric solution.

In addition to that we've got mechanical ventilation and heat recovery, and we've also got an inbuilt grey water recycling system, we've got triple glazed windows, very efficient triple glazed windows brought in from Scandinavia, and we've got some quite innovative materials called phase change materials which regulate the temperature of the house to prevent summertime overheating. So, some quite cutting-edge materials and processes in the house.

Scott: Just quickly I'll say that level five of the code for sustainability homes means mean carbon neutral space heating and hot water reduced to zero emissions as well, is it, and lighting and ventilation?

Stewart: Yes, light and ventilation and space heating are all carbon neutral. To achieve code level six which is absolutely zero carbon and there's only…since we've built the Sigma Home there has been two code level sixes built, and they fully offset all of the carbon generated from the electricity used from unregulated appliances like the TV, your various other electrical appliances.

Scott: The Sigma Home was built and it was displayed in the…is it the BRE Innovation Park, back in 2007?

Stewart: Yes, we designed and built the house the tail end of 2006, it was opened in June 2007 by the UK Housing Minister, and it's on display at the BRE, which stands for the Building Regulations Research Establishment, in London, and on there there's a number of houses built, all of which have got various levels of code compliance and so eco-friendly features. It's become quite a big thing in the UK as a bit of a centre of excellence for research and development and innovation.

Our job is not stopped just at building the house, we've actually continued a full scale research program on it, and we've actually been monitoring the as-built performance, and most recently we've completed post-occupancy evaluations where we've actually had a family living in the home during the four separate occupation periods over a full calendar year. And that's very cutting-edge, that's quite groundbreaking in terms of actually, ‘Does the house do what it was designed to do and do people like to live in them, is the air quality good, is the environment quite good to live in?’ And that study has just been completed in June this year and we've just published our outcomes from that recently to aid the UK developers bring about these houses.

Matthew: So, you've had these families in there and you've been monitoring how they actually use them in practice. You found that some of the things didn't meet the expectations that you were hoping for, like the actual energy consumption on site, but you're going to continue the project by building a new Sigma II House concept?

Stewart: Yes, absolutely. For us I mean it's very much about you know this is a test bed, it's a research project, well, we have built this highly innovative, groundbreaking house. Really it's about how do we take it to market and does it work? And what we've found from the learning is that the energy consumption in the house is actually 40% more than it was designed to, so even though we have a lot of features in the house, it's actually burning more energy than it was designed to do.

There are three main reasons for that. One is the fabric, the building envelope is not performing as good as it was designed to, and we've got weak points through thermal bridging, through air leakage, through the fabric, and due to complexities of workmanship and supervision and the type of materials used.

The second thing is that the users of the property, so actually the people living in the house, are not optimising the technology. Basically they are very confused. The controls have a lot of buttons, have a lot of control panels, and they're really quite confused. They want a 'keep it simple, stupid' approach and they want an 'on/off' button. Anything more complex begins to run away from them. That's been a source of actually using more energy than it should do.

And the last thing was the micro-renewables generally have been underperforming, which is mostly due to the micro-wind that we've got on the house, we've got two wind turbines, and some of the solar thermal has not been balanced with when the family want to use the hot water and the heating, and generally it's been generated during the day but because they work during the day and the kids are at school, it has limited storage capacity to actually get the benefit and use it when they want it, which is first thing in the morning or late evening. So, it's been fabulous research and quite cutting-edge to get to that level of detail.

We've also got 40 to 50 sensors in the house that measures relative humidity, VOCs, off-gases, air quality, air temperature, air movement, to look at the internal thermal comfort of the house. So, in the UK climate we're looking to keep things cool in the summer and hopefully warm in the winter and the house needs to be able to flex to suit those comfort levels for the occupants.

Clearly, if we're building a very airtight structure where we're keeping the energy in the house, also it's a draught-free house, we want to make sure there's no issues with health problems in the future where you've maybe got poor air quality, poor air movement in the house because you're not ventilating it correctly. And these things are quite prominent in our minds before we roll the product out at a mass level. But they're certainly our ambitions moving forwards, having now done the sort of road-testing of the house.

Scott: We're speaking to Stewart Dalgarno, he's the business development director of the Stewart Milne Group, and they're a housing a construction firm in Scotland.

It's interesting to hear just how much monitoring you've been doing over the last two years, and it's great to know that these…okay, it didn't perform as well as you wanted in some areas but it's given you something to work on now, and we're very much looking forward to seeing how the Sigma II goes. One of the problems you mentioned was the building's envelope performance and you had a problem with thermal bridging. Can you just explain that to the audience, and also to me because I don't really know what thermal bridging is?

Stewart: Well, thermal bridging is essentially where you've got a hard point in the building where heat loss will move from the inside to the outside. So if you've got, for example, a lightweight timber frame structure with insulation between the wooden studs that form the external wall, the stud is essentially a solid piece of wood and you will lose energy through that component. Clearly when we've done a lot of thermal imaging in the house and we've done co-heating tests where we heat the building, we've been able to ascertain the as-built heat loss parameter for the house. Thermal bridging has been a key issue.

Moving forward, one of the things we've done is essentially looked at materials which isolate the inner and outer skins of the building, and therefore we've got a bridge that prevents heat loss across the structure and therefore retained it within the house and therefore keeps the energy demand low and prevents excessive use of gas boilers, et cetera for heating purposes. A very important part of good envelope design.

Where you've got perhaps junctions with floors you get a lot of heat loss through the junction where there's quite a lot of materials used in there and it's difficult to get insulation into these areas, and we've been working on a build system called Sigma II which has got greatly improved details whereby most of the details include quite a lot of insulation and therefore you keep the heat in the building.

Matthew: And what's your timeframe for Sigma II to be built, and then from there how long until you think that you could hit market with a product that's similarly priced to what people are paying for houses today?

Stewart: Well, absolutely, we've got our first order through for Sigma II. We've got a project for 50 houses, and we've got about 300 to 400 houses on our radar over the course of the next couple of years where they're looking for these super performance levels. Clearly there is a huge market in the UK, 170,000 houses every year in England alone, and there's a demand for almost 220,000 houses, so there's a great undersupply of houses and we're already speaking to some of the major house builders about how we scale up production. Currently, the Sigma Home is about 40% more expensive than the conventional home in the UK, and therefore it's not really a commercially viable rollout at this stage.

However, moving to more low energy as opposed to low carbon homes we think is a step in the right direction, and we're targeting bringing out a low energy house to the market that may be 3,000 to 4,000 pounds more expensive than the conventional house in the UK. And once we get volume of those going and we move our timber frame production to that, which is likely over the next two or three years, then we start to decarbonise the home by bolting on micro-renewable technologies or a common heat and power solution at a development level where you've maybe got 100 houses being powered up by a micro solution, a small energy centre.

Matthew: So, would that mean that this option that's only, say, 4,000 pounds more, would that be pretty much similar to the Sigma II but without the additional micro-renewables cost on top?

Stewart: Yes, we're very much focusing on a fabric…what we call a 'fit and forget' fabric solution, without the temptation to put micro-renewables onto the house at a plot level. We think just building a very, very good fabric in the first place is the way to go, because if you can control that it's easy for the customer to see essentially hidden technology, it's there forever, and just building a good shell in the first place is certainly where our focus is.

Moving forward and once we get the volume of that sort of solution going, we would then look to bolt on more of the micro-renewables. We still think there's a little bit of emerging technology there, so they're not fully proven yet and they're not robust, they're expensive, and there's a long return on your investment. And at the moment the way the market is, most countries in recession are hitting the world economic downturn, it's not going to be a proposition you can bring to market in the foreseeable future. But certainly a low energy one with a good fabric has got the legs, has got the commercial viability, over the course of the next two or three years.

Matthew: It seems like a very good focus to go with the building fabric because it's a bit difficult to change after you've built it, but you're certainly leaving the good facing areas so that you can add the renewables afterwards if someone wants to retrofit them in in ten years time when the price is down.

Stewart: Absolutely, yes, we think that seems to be the way to go at the moment. The Sigma I, it's a full technology solution, but that's not going to be the proposition unless the UK government incentivise the use of renewable technology through what's known as a feed-in tariff, so you actually get investment for your renewables and you then generate power and you feed that back to the national grid. But that's some way off in terms of legislation that's got to come through, and that's similar to what they do in Spain and it's similar in Germany and similar in France where these feed-in tariffs seems to work quite well.

But that's some way off, and we think just going for the good fabric which is probably similar to if not slightly more than passive house standards in Germany, Austria, Switzerland and the Scandinavian countries, they're very adapted at producing low energy houses and they are probably ten years further down the road than we are, but if we can bring about those similar standards for all houses in the UK then that is a significant step in the right direction for our carbon footprint.

Scott: In the domestic market there, Stewart, is there, hopefully…it would be nice to think there's some healthy competition between your company and other companies to actually build these sort of low carbon houses and ultimately zero carbon houses.

Stewart: Absolutely, there is good competition across all the house builders and the supply chain. The challenge to get to zero carbon is quite a significant challenge, and with a recession currently, one of the ways that we've looked to continue to invest in this program or work is actually through some collaborative research and development with our competitors. It's the first time in the UK that competing developers have actually come together to say, 'No single person will be able to deliver all of the solution but collectively we can.'

Our organisation is part of a consortium who is bidding for innovation and research funding from the UK government to develop this mass rollout of low energy homes, and we're bidding for the 6.2 million pound research grant to develop technology at a mass level. And between ourselves, there’s only three developers and two major suppliers. We've got something like 20% of the market, potentially could be changed with a little bit of support and help from the UK government in terms of cash and funding.

So, difficult times mean new ways of working and we're all trying to come up with the same answer, but whilst healthy competition is there I think everybody realises that collaboration is also a positive thing and is also a new way of working for the sector.

Scott: Well, it’s good, you know I can't imagine, being an Australian, the housing and construction sector collaborating together to do something that's good for society. It's quite a shock to me, but it's good to hear that's happening over there.

Stewart: This is quite groundbreaking. As I say, it's the largest single consortium, and the first time the government has funded a collaboration agreement within the sector. It's quite common in other, maybe automotive and maybe aerospace, where they're looking to bring about new techniques and typically they need to collaborate to develop that and leverage their supply chain.

So, that model is coming across from the automotive and the aerospace sectors, and we're working with the UK government to move that forward during these leaner times when it's more hard to continue to invest in these sorts of solutions.

Matthew: We're just about out of time, so I was just wondering whether we'll see Stewart Milne's amazing building fabrics in Australia and if there's any possibility there once you've ironed out the last of the bugs? And do you think there could be a future where we have these, sort of at least on heating, autonomous heating and cooling, zero carbon houses for all our housing?

Stewart: My personal belief and the company's view on this is that there's a certain inevitability that we're going to have to move down this road and therefore the opportunity presents itself. If we can come up with an affordable proposition, take it to market, and then clearly there's a clear commercial business case for doing it, and we believe the solution is there.

Exporting is always something that's on our mind, and clearly the UK government, if we can become a centre for excellence for low energy housing, would want us to export. Perhaps into Europe first and then, who knows, we could be in Australia before you know it, and maybe franchising or doing some technology swaps with house builders in Australia.

Matthew: Fantastic, and we really look forward to that.

Scott: Stewart, we'd like to thank you very much for speaking with us this morning and we look forward to seeing the Sigma II up and running, and we'll probably be in contact again to find out just what the stats are on that because we're impressed with the fact that this thing was introduced into the innovation park, you monitored it for two years, had people living in it, and you've got some results now, some good and some not so good, and the 'not so good' you're working on to make a better house. We're pretty impressed by that. That sort of stuff doesn't happen in Australia with housing and construction. So, we really do wish you all the best of luck with that.

Stewart: Thank you, thank you very much.

Scott: Thank you very much. We've just been speaking to Stewart Dalgarno, he's the business development director for the Stewart Milne Group. And you can learn more about Stewart Milne and the homes they build at www.stewartmilne.com, and once you go there you can click on the 'Sigma Homes' button. Obviously look at all of the website because there is some good stuff, but we're particularly interested in Sigma Homes, and learn more about this fantastic eco house.

Transcript by Julie Burleigh

Links:

Stewart Milne Independent House Builders

BRE Innovation Park