An Eco Home on a Budget

Architect Andrew James was ahead of his time when he started planning a house which would be eco-friendly and open plan. “We came back to Britain from Vancouver in Canada where energy efficient homes and spacious designs were commonplace,” says Andrew. “Over there, temperatures can plummet to minus 40°C so, even as a young man, I was going to seminars about passive solar awareness in relation to the home.”

Determined to build a family house which would accommodate as much as possible of what he’d learned, Andrew and his wife Louise started looking for the perfect plot. “It had to be south facing, gently sloping, full of trees and close to a decent pub,” he says.

They found the ideal location in a village orchard near Easingwold in Yorkshire, which had permission for a house approved in principle by Hambleton District Council. The only stipulation was that the dwelling had to be built close to the road in keeping with other buildings in the village.

Andrew started work designing a low-energy, space efficient chalet style property with rooms in the roof and low overhanging eaves. Following the basic principles of passive solar design, windows were optimised on the south facing elevation to maximise solar gain, and kept to a minimum on the north elevation where they would lose most energy.

By the time Andrew and Louise had managed to gain planning and building regulations consent and were ready to start building, 18 months had passed. They had moved into a caravan on site, a cost effective option that also proved highly practical, as Andrew planned to do much of the building work himself in order to keep down costs, including digging the foundations and laying the foundation slab which he and the builder did between them.

Andrew chose to build using a timber frame rather than the more conventional brick and blockwork. As a skilled carpenter and furniture maker, using timber seemed like a perfectly logical choice. The frame he chose is of standard 89mm stud depth, filled with mineral fibre insulation. Inside this, however, Andrew has created a second insula - ting layer using foil faced, polythene bubble-wrap insula - tion fixed to the inside of the frame with spacer battens behind the internal plasterboard finish. The battens used are sufficiently deep to leave a clear airspace behind the plasterboard, both as a convenient service duct for plumb - ing and wiring, and also to allow the reflective foil to function — the foil only reflects radiant heat if there is a void in front of it. The joints in the polythene insulation are taped together using reflective foil tape to create an airtight seal and vapour control layer.

“The thermal performance of the house is to a specifi - cation which still exceeds the latest building regula tions,” says Andrew. “The whole thing about designing and build - ing energy efficient houses is that the air tightness and fitting of the insulation is absolutely critical. If you are not a perfectionist, the whole principle is wasted because it will leak air all over the place and along with it, the heat. That was the reason we wanted a timber framed house. It was easier to make airtight and insulate to the standard we required.”

Effectively the house works like a large, airtight survival blanket. The rate of air change, other than from the opening and closing of external doors and windows, is controlled using a mechanical assisted ventilation system. This extracts damp stale air from the bathroom, toilet, kitchen and utility room, with incoming fresh air supplied through trickle vents in the habitable rooms. Hot water heating is supplied to an underfloor system by a Tri-Save Turbo 45 condensing boiler and the house, which measures around 150m², has a heating cost which has averaged less than £300 a year.

All of the windows, apart from the Velux rooflights upstairs, were designed by Andrew and made in Douglas fir by a local joiner, they incorporate shoot bolts and stainless steel friction stray hinges. The Douglas fir doors open onto the red cedar decked outdoor area, the front door was made in Andrew’s workshop. “The porch is a significant part of the house because I wanted to design it in a way which drew people in, but maintained a link with the outside,” says Andrew.

Outside, the walls are rendered. Andrew applied the render onto galvanized steel mesh, fixed to pressure treated timber battens to create a vented cavity, over a breather membrane on the plywood sheathing.

The softwood roof timbers were cut on site, insulation is installed at ceiling level, in conjunction with the same foil faced bubble wrap system as was used in the walls. The roof areas are floored to provide large, easily acces sible storage space. Unusually for this country, the roof has a 1.5 metre overhang on the south side, giving protection from the intensity of summer sunlight and avoiding the risk of overheating whilst maximising the solar gain and light from the low angle winter sun. “Light is very impor tant to me,” says Andrew. “When you are working with a very small volume you can use natural daylight to draw the eye from a small space into the adjacent space to make the overall area seem bigger. The lighting has been a huge success in this house – it varies with the seasons and transforms the interior in different ways all year round. This house is everything I could have wanted – and more.”

Further reading:

• Great Green Homes
• Alternative Heating
• Eco House Design

Find out more about building an eco home in The Homebuilding & Renovating Book of Green Homes