Exterior of the Grand Designs self-heating house in Bletchley

The pioneering self heating house

Andrew and Margretta Smith's innovative house nestles in an earth bank

By Emily Brooks | 27 January 2021

The Grand Designs self-heating house is the first of its kind in the UK. It’s set into a sloping site and covered by several hundred tons of earth. Built by Andrew and Margretta Smith, the house is a lesson in how to make a house unobtrusive in the landscape. But the blanket of soil isn’t just about appearance, it is essential to the way the concrete building maintains a comfortable temperature all year round. It acts like a giant storage heater.

Andrew and Margretta moved to his parent’s cottage in Buckinghamshire after they passed away. Although this was a decade ago, a self build project had long been the plan. It took the couple three years to get planning permission. Not because of the experimental nature or modern appearance of the house they wanted, but because it’s located outside the village’s designated building boundary.

Overhead view of the turf covered self-heating house set into a bank of earth

The house is covered in turf from the excavated site. Photo: Jefferson Smith

Inter-seasonal heat storage

Andrew has a PhD in low-energy systems and was keen to use an innovative and experimental self heating system. The building is built into an earth bank which, during the summertime, soaks up enough heat to raise the internal temperature through the winter.

‘With most homes the walls, roof and floor are insulated to stop warmth escaping. But I want heat to come through the house and also sink into the earth. This means the hundreds of tons of soil will gradually warm up. I think in about two years’ time we won’t need to heat the house at all,’ says Andrew. ‘Until then, there’s a woodburner with a back boiler, plus a small air-source heat pump. We also have some solar thermal panels for the hot water.’

Exterior view of the house showing the turf roof, glazed sliding doors and internal courtyard

The timber cladding is western red cedar. Image: Jefferson Smith

The long game

Planners approved the project in May 2018, and the build got underway. Andrew took on the role of project manager. About 60 per cent of the house backs straight into the earth behind it. A courtyard layout brings light to this side of the building. The remaining glazed, rendered and cedar-clad right-angled façade faces the garden. Andrew and Margretta designed their home with help from an architect who refined their ideas and prepared the technical drawings.

The walls are stainless steel formwork, with timber formwork for the roof. These are filled with GGBS concrete made of 60 per cent ground granulated blast furnace slag. This is an industrial byproduct that is more sustainable than standard concrete. A structural engineer vetoed plans for prefabricated panels. He had concerns about weak spots where the panel joints would be under pressure from the weight of the earth.

Overhead view of the courtyard garden at the centre of the Grand Designs self-heating house

A courtyard at the centre of the house brings light into the interior. Photo: Jefferson Smith