In the past year the world’s biggest climate change laboratory has been testing Britain’s homes of the future. In a giant black cube near Manchester, scientists mimic the weather to see how two prototype new-build houses perform. The first results are in and they show that big housebuilders can build homes fit for the climate emergency.
Inside Energy House 2.0, a £16 million temperature-controlled chamber at the University of Salford, a pair of detached three-bedroom houses stand side by side. In an unusual collaboration between two of Britain’s biggest housebuilders, one house is by Bellway and the other by Barratt — both were built with materials from the French company Saint-Gobain. Here, the researchers can blast the houses with every type of weather, from gale-force winds and snow storms to 40C heatwaves and -20C blizzards.
These tests will reveal the most cost-effective ways to cut carbon emissions and energy bills in new-builds. Both houses closely match the government’s proposed Future Homes Standard, which will apply to all new homes from next year.
The standard is designed to cut carbon by up to 80 per cent compared with 2013 rules, and will require heat pumps for all new homes. Ministers are also consulting on solar panels, extractor fans and systems to recover heat from waste water in all new homes. It could save homeowners between £200 and £2,120 in energy bills a year, according to government plans published in December.
The technologies tested in Salford will be “locked into” the Future Homes Standard, Richard Fitton, a professor of building physics at the university, says. “We’ve got something that’s going to have a big impact.”
Advertisement
It will also influence what we can do to retrofit our homes. Fitton’s team is testing how different types of insulation, heating and ventilation stand up to a changing climate. The findings will show what works and what is not worth spending money on.
Barratt’s eHome2 pitches an air source heat pump against infrared heating in the shape of flat white panels and mirror heaters, which feel like the sun warming your skin. Bellway’s prototype, the Future Home, has no fewer than six types of heating system including a Worcester Bosch 3400i Hydrotop air source heat pump fitted invisibly inside the roof space.
The more you insulate, the more you must ventilate, or risk damp and mould. In each prototype house scientists are testing mechanical ventilation and heat recovery (MVHR) against a simpler system. Each MVHR system has a bulky machine and extensive ducts to extract stale air, which use heat from it to warm fresh incoming air.
In the Barratt house, the MVHR’s rival is a centralised unit in the loft that pumps moist air from the kitchen and bathrooms outside, while fresh air comes in through trickle vents around windows. Bellway’s alternative is a decentralised system with Titon extractor fans in the kitchen and bathrooms. The heating and ventilation test results are still to come.
First the laboratory tested the biggest difference between the two houses: the fabric of their shells. “This is not what a lot of people are interested in. The talk is around heat pumps and infrared,” Fitton says. Yet arguably, the fabric of a building is more important. It is what will stand for centuries to come.
Advertisement
Both homes are highly insulated, with top energy performance certificate (EPC) ratings of A. While the Bellway house’s structure is more traditional, made from brick with a combination of non-combustible mineral fibre and polyisocyanurate (PIR) wall insulation, Barratt’s uses innovative materials. Its timber frame has I-shaped beams (scotframe.co.uk) with more room for factory-fitted, non-combustible mineral wool insulation. Outside, a thin layer of Weberwall brick-effect sheets are plastered on — these are less carbon-intensive to make and up to three times faster to fit than slips cut from real bricks.
• The eco-pile: Britain’s first net-zero stately home
How did they fare? New homes have a performance gap in the amount of heat they are expected to lose under their design versus what actually happens once they are built. This gap can be between 6 per cent and 140 per cent, according to data published by Leeds Beckett University.
The prototypes tested in Salford “performed very well” by comparison, Fitton says. Barratt’s house has a performance gap of 3.9 per cent, while Bellway’s gap is 7.7 per cent. “We expected our houses to try hard, but these are prototypes. The first time you do something, it’s not perfect. The important thing this tells us is that we can build this type of home, and we can build it at scale,” he adds.
To test heat loss as a whole, Fitton’s team sent the temperature in their lab plummeting to 5C. “Then we put a lot of heat into the house,” he says. They heated each home to 24C inside and measured how much energy it needs to stay that warm when it is 5C in the chamber outside.
Advertisement
In Barratt’s eHome2, the main cause of the performance gap was a small error in how insulation was factory fitted inside the wall panels. It was pushed into the corners, “like tucking in your duvet”, which compacted the insulation, says Oliver Novakovic, technical and innovation director at Barratt. “Because it’s a highly energy efficient home, any minor mistakes have a much bigger impact. There’s much less room for error,” he adds. The manufacturer changed its processes to fix this mistake.
• Live guilt-free in the ‘greenest’ home in the world
According to Barratt’s modelling based on the performance gap results, it would cost £88 a month to run eHome2 — slightly more than the expected £83.50. “That’s much better than £250 to £300 for a Victorian home,” Novakovic says. The figure includes lighting, heating, hot water and fans, but not appliances.
Fitton says Bellway’s performance gap is largely due to the unusually high number of holes made in the walls and roof to fit its six heating systems — with about 150 sensors to test it all. Jamie Bursnell, group technical and innovations manager at Bellway, says the results are “very encouraging and allow us to be confident of delivering homes at scale under the new Future Homes Standard. We have learnt lessons throughout the project which we will incorporate in future designs.”
Both housebuilders say they will use the results to improve their products before building them in large numbers. They will also publish the findings to help Britain move towards net zero emissions.
