Solar nexus

IT FIGURES THAT THE DAY I'm meeting architect Lorn Macneal on the site of an Edinburgh newbuild featuring renewable energy systems – notably solar voltaic panels for generating electricity – it's chucking it down. Luckily, by the time I arrive at 139 Grange Loan the rain's stopped, but it's all puddles and mud. Accessing the house involves an ungainly scramble over a network of planks.

Much of the super-structure is up, yet you have to use your imagination to envisage this massive family home of some 4,000sq ft, boasting five bedrooms, three reception rooms, three bathrooms, a double garage and a garden room. What's intriguing isn't the size – hardly unusual at this end of town – but the architect's commitment to eco-friendly solutions as a way of futureproofing the house against rising energy prices while reducing the house's carbon footprint.

For a start, the house is built "upside down," both to optimise the glorious views out over the grounds of the Astley Ainsley hospital, and because heat rises. "We're creating maximum use of sunlight and getting more warmth into the upper space. The bedrooms are heated in the morning and at night, and that's enough."

The greenhouse effect is often misquoted, says Macneal. On a local scale, trapping the sun's rays indoors is a good thing. "It's what makes your tomatoes turn red. That's not an environmental issue, that's a beneficial issue. You're using that heat to warm the house. When you're designing a house you look to see where you can place south and south-west-facing glass to create warmth, while also making sure you don't make it intolerably hot inside."

Once warm, this well-insulated house will suffer minimal heat loss. "Under the concrete we've put six inches of insulation, six inches in the walls, and in the ceiling, ten inches. Windows are all double-glazed E glass, the highest level of efficiency."

He made a pragmatic choice to go with urethane insulation, instead of fashionable sheep's wool. "Wool's good, but not a great, insulation and the cost is significant. Yes, it's readily available, you don't have to create it, but urethane offers much higher levels of insulation, so ultimately you have a better gain in the carbon footprint. I'm not an eco-geek. I'm using urethane because it works."

The house will contain a grey water recycling system that gathers rainwater from roof gutters and stores it in a tank which is plumbed for reuse in flushing toilets and the garden hose. It will also have underfloor heating, chosen because it functions at a lower temperature – around 42C, rather than the 60C-65C that comes out of a standard radiator.

"You can have it on at a very low setting all day long, giving out heat sufficient to raise your body temperature without heating the room right up to the ceiling," says Macneal. "You don't need a huge amount of energy."

And all this heat (plus the hot water) will come from a ground source heating pump. I'm curious to see this marvel and a bit underwhelmed when Macneal points out a pair of black rubber hoses inside the back door. Nearby is a tangle of white pipes, labelled kitchen, master bedroom, etc.

"This technology's been used for decades in Scandinavia and Germany but it's only been noticed here in about the past five years. There are several ways to access the heat. You can bore 100 metres into the ground, making a hole about six inches in diameter. That's the neatest way.

"Another, less expensive method is to go into the ground about one metre deep and set the pipe under the surface. Or, if you have water nearby, you can actually put the pipe into the water, as long as it's about one metre deep. You're drawing heat out of the fluid underground. You see, even in the winter the ground isn't frozen all the way down, there's general warmth below. You could do this in Alaska. And although you need electricity to run the pump, for every unit you use, you get between four and five units back."

A series of solar voltaic panels will be situated on the roof to generate electricity. "We'll still have to buy additional electricity, but during the day and in summertime we can export energy back to the grid. The bills will still be significant, but they'll be far more contained than they'd normally be over 15 to 25 years." (For more about ground source heating and solar voltaic panels, see panel, right.)

Macneal admits that going off grid for energy makes more instant economic sense in the country than it does in the city, where there's easy access to a gas network. But as we've seen, all energy costs are on the rise. "This heat pump and boreholes cost 17,544 less a 4,000 government grant, and the solar panel system was 6,500 less a 2,500 grant," he says. "Yes, the economic payback is marginal, and a lot of cynics ask what it's worth and why are we doing it. I say well, it is a way forward and you can either sit on the fence and do nothing, or you can say, let's contribute. If you do good, you feel good. And the house will still have a smaller carbon footprint."

Macneal says he's ultimately doing this for his kids and their peers. "It's important to me to educate my children – it's not my life, it's future generations we're accountable to. I have friends who are sceptics but I'd rather believe in this."

Lorn Macneal Architects; 3 St Vincent Street, Edinburgh, tel: [phone], www.Lornmacneal.co.uk For information about solar and wind applications visit www.solarwindapplications.com