The zero carbon house: Ten years on

On Shetland’s northernmost inhabited island, Unst, a pioneering project aimed at demonstrating practical ways of reducing carbon emissions has recently passed its tenth anniversary. The Zero Carbon House, at Uyeasound, has inspired developers elsewhere and changed government attitudes to, among other things, air-to-water heat pumps. But, as I discovered when I met its owners, Michael and Dot Rea, it remains a work in progress.

There’s no longer any doubt that climate change is upon us, as this NASA page explains. Here in Shetland, the warming trend is noticeable. Climate scientists are overwhelmingly of the view that action is needed if we’re to avoid huge disruption to life on the planet. However, more than 20 years since the Kyoto framework was agreed, the upward trend in temperatures is continuing.

Emissions from housing account for around 40% of the UK’s total carbon output, so finding ways to reduce them is clearly a priority; and that was the challenge that Michael and Dot took on.

If there is a creative or inventor’s gene, Michael clearly has it. After studying painting and sculpture, he worked in London with Henry Moore and Barbara Hepworth, then spent some time in stage design alongside Trevor Nunn, then a trainee producer.

Then he “accidentally got into electronics.” Westinghouse wanted an artist to paint circuits onto printed circuit boards. It had to be done under a microscope and he did a job estimated to take 3 months in just over 4 weeks. Only afterwards was he told that he’d been working on the Chevaline upgrade to Polaris missiles ‘so I hope I got it right!’ There were all sorts of other projects, including – twenty years ago – an LED-equipped warning triangle that was too far ahead of its time for the then Department of Transport. There was a simple but ingenious device to help gardeners sow seeds in a straight line and at a constant depth.

After a varied career in invention, it’s understandable that Michael would want to tackle the biggest global challenge of our time. But why Shetland?

The story begins in 1981, when Dot attended a course at Lerwick’s Anderson High School on spinning, weaving and hand dyeing. She liked Shetland very much and persuaded Michael to visit with her two years later. They were struck by the welcome. As Michael recalls, “We went to the yachting regatta dance and the locals said, ‘Well, will you come and live with us?’”

An immediate move was out of the question, though, because Michael was caring for his elderly parents. In 2000, after both had passed away, the couple’s son posed the question: ‘Well what are you going to do? Are you going to just talk about Shetland, or are you going to move up?’” They sold their house and bought one – over the phone – in Baltasound, the main settlement in Unst.

The basic kit went up in less than five days, in November 2006, and the house was completed in March 2008. It wasn’t an easy site to develop; a lot of excavation and drainage work was needed. There were some remains of a former Hanseatic trading booth, including a constructed well, about six metres deep, that survives today. The water analysis shows quite a high level of sodium and lots of nutrients.

What features make this house so special in environmental terms? To begin with, the choice of a timber structure involves a renewable resource partly composed of stored carbon. Less carbon was emitted during construction than would be the case if concrete (here used only for the foundations) had been employed.

The walls and roof are heavily insulated using 140mm of Celotex expanded foam and the double-glazed windows are filled with argon. There is a heat recovery system that recovers warm air from the house’s air conditioning.

The water heating – a major emitter of carbon in conventional homes – relies heavily on air-to-water heat pumps; one has been in place from the beginning and a second is about to be commissioned. These feed warm water into a very large thermal store, the water in which is also heated by an immersion heater powered by a small vertical-axis wind turbine that, rated at about 200w, produces about 5 Kw/h in an average day. The small white turbine and the large thermal store can be seen in the photograph above. The pre-heated water is then heated further by an in-line, instantaneous water heater; but it has very little work to do.

LED lighting, now commonplace, has been part of the house from the start. There are other innovations. Sewage is dealt with by an anaerobic digester, rather than in a septic tank. The house is well-connected, with satellite broadband, internet phone connections and a 4G mobile signal.

Michael and Dot grow food, thus reducing transport carbon emissions. They use raised beds, heavily-constructed cold frames and a greenhouse with twin-wall polycarbonate glazing and a heavily-insulated solid floor, which stores heat.

All of these efforts have given the couple a home that not only makes minimal impact on the planet, but feels very comfortable. When they take a break from writing or answering queries (in Michael’s case) or carding and spinning (in Dot’s) they enjoy a beautiful view over the bay through the large windows.

But it’s still a work in progress. The next physical change involves adding decking to give more usable outdoor space. However, Michael is in inventive mode again, this time working on an electricity generation system employing fluid dynamics.

There’s always been a great deal of interest, worldwide, in the house and its technologies. Just after it was completed, the Guardian visited and made a video about the project, which led to an avalanche of enquiries from all around the world. Italian television had visited not long before I called. The house also has its own website.

Michael continues to provide advice world-wide, and he doesn’t charge for it. He reckons he’s probably provided four or five hundred informative items for universities. A housing developer has built an estate in Sydney that embodies lessons from the Uyeasound project. Michael helped a group of like-minded employees from Microsoft track down funding from the US Government.

Back in Unst, the house is in good company. A few miles up the road, the PURE energy project has long blazed a trail in the development of renewable energy and, in particular, the use of hydrogen fuel cell technology. Like Michael, the staff at PURE have been developing solutions, and offering advice worldwide. Islanders are also pursuing a possible opportunity linked to space research.

It might seem surprising that one of the corners of the UK remotest from large centres of population should occupy a place on the leading edge of scientific progress. But this is an island which has, in the past, had links with – among others – Charles Darwin, Arctic explorer John Franklin and a French government scientist’s efforts to measure the curvature of the Earth.

No wonder Michael and Dot can feel so very much at home here.