Grand Designers Andrew and Margretta aim to create a self heating earth house - the first of its kind in the UK. 

Kevin with Andrew & Margretta at the Bletchley self heating House - grand designs

Image: Channel 4, Emily Brookes

The fourth episode in 2021's series of Grand Designs sees Kevin McCloud meet Andrew and Margretta, a couple who plan to build a self heating house that stores up heat in the summer to heat the home throughout winter.

While Andrew and Margretta moved to Buckinghamshire a decade ago after his parents passed away, a self build project in the area has always been the plan. It took the couple three years to get planning permission – not because of the experimental nature or modern appearance of the build, but because it’s located outside the village’s designated building boundary. 

Set into a sloping site and covered by several hundred tons of earth, 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 building maintains a comfortable temperature all year round. Built of concrete, the house acts like a giant storage heater.

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Inter-seasonal heat storage

outside view of bletchley self heating house - grand designs tv house 

To preserve the site’s biodiversity, its turf was replanted on the roof. Image: Jefferson Smith

Andrew has a PhD in low-energy systems and was keen to build a house using an innovative and experimental self heating system. The house is built into an earth bank which, during the summertime, soaks up enough heat to raise the internal temperature of the home 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, so that the hundreds of tons of soil 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.’

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The long game

 front view of self heating self build in bletchley - grand designs tv house

The house’s exterior is clad in western red cedar. Image: Jefferson Smith

Planners approved the build in May of 2018, and the build got underway with Andrew taking on the role of project manager. However, with the complexity of the project causing difficulties with contractors and budget constraints, not to mention the onset pandemic, the build faced its fair share of challenges.  

About 60 per cent of the house is backed straight into the earth behind it, with the remaining glazed, rendered and cedar-clad right-angled façade facing the garden. A courtyard layout brings light to the back of the building, where it is surrounded by earth. Andrew and Margretta designed their home with help from an architect who refined their ideas and prepared the technical drawings. Andrew acted as project manager and main contractor for the build, bringing in the tradespeople and working alongside them.

The walls were made using stainless steel formwork, with timber formwork for the roof. These were filled with a concrete made of 60 per cent ground granulated blast furnace slag, known as GGBS, an industrial byproduct that is more sustainable than standard concrete. The original plan was to use prefabricated panels, but that was vetoed by the structural engineer over concerns about weak spots where the panel joints would be under pressure from the weight of the earth.

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 Pale walls and a polished limestone floor help to bounce light around the living space Jefferson Smith

Sticking to the budget

Switching to an on-site poured concrete used up the contingency, so Andrew had to make sure everything else kept to budget. The couple funded the build using savings and by remortgaging the cottage. Shopping around proved key. ‘It opened my eyes to how wildly prices can vary, even for big things like windows which you’d think would be uniform,’ says Andrew.

With Margretta’s job on hold during the pandemic, she was able to get involved on site – rendering the exterior, taping up plasterboard and painting. Andrew estimates that, between them, their efforts saved around £200,000. The final build cost came to just £310,000, which is not bad at all for a house with four bedrooms.

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 Black ceramic floor tiles under the dining table absorb the warmth of the sun, passing it to water pipes which flow to the hot water tank Jefferson Smith

Natural benefit

With rosy-toned western red cedar cladding and the site’s biodiverse turf on top – carefully scalped and put to one side by Andrew – the finished house feels like a part of nature, even with its mass of glazing. ‘There was a muntjac deer on the roof the other day,’ says Andrew. ‘When Margretta and I were in the living room, we both said it was like being in a bird hide, there were so many birds flying backwards and forwards.’

With thanks to Twig Nurseries and Michells Trading for supplying plants and pots.

Watch along, and let us know your thoughts on TwitterFacebook and Instagram

This episode first airs on Channel 4 at 9pm on Wednesday 27th January. You can find the full preview of this series of Grand Designs in the January issue to read online for free 

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