There is a patch of wasteland at the end of a terrace in Crouch End where, in less than two weeks’ time, a two-bedroom home will complete the street. This won’t be the work of round-the-clock brick layers and break-neck plasterers, but a team of carpenters inside a shed near the Welsh market town of Welshpool.
The timber house has been delivered as a flat-pack of over 100 parts on the back of three articulated lorries and craned onto site. The jigsaw of parts will be assembled like a piece of Ikea furniture over the course of the next week — shaving months off the traditional build time for a brick and concrete home.
The house is designed to Passivhaus standards, a type of highly insulated and airtight construction that almost eradicates the need for central heating in the UK climate. The design also uses Modern Methods of Construction (MMC), which sees more sustainable timber components produced inside a factory rather than using labour and energy-intensive on-site techniques like brick laying.
When complete, it will be home to the architect Jonathan Wilson, who has long wanted to build his own eco-house in his beloved north London neighbourhood.
“I’ve always dreamt of building my own house, and I was interested in doing Passivhaus because I’ve always been interested in sustainable building,” he says.
Wilson is a trained architect, but he brought in a specialist design team led by architect Tom Mason (circlearchitecture.co.uk) for the daunting Passivhaus certification process, which requires rigorous testing of the building’s energy performance and onerous documentation. “There’s no way I could have done it. There’s a scientific process of testing the design — that part of it was absolutely essential,” says Wilson.
“You have to know what you’re doing. Even though I’m an architect I’ve had to employ another architect to do all the technical design and the Passivhaus modelling, which is quite complex and requires some special software.”
The components of the house have been made almost entirely from engineered wood and manufactured off-site by PYC Construction (pycconstruction.co.uk), which specialises in timber and Passivhaus buildings. The wooden walls contain a thick wodge of Warmcel, an insulation made from recycled newspaper, which makes up 90 per cent of the wall thickness.
The house will stand on concrete foundations but almost half of the concrete for this build has been replaced with GGBS, a waste product from the blast furnaces used to make iron. The whole thing has been covered in a thick layer of expanded polystyrene blocks to insulate the building from the ground.
Hefty insulation will stop heat escaping from the home and, with triple glazing, solar panels and an air source heat pump, will slash Wilson’s future energy bills. But thick walls come at a cost on an inner city site. “That’s a problem on a site which is so constrained, it’s not like I can just expand the walls outwards, they actually take space away from the inside of the building,” admits Wilson.
He bought the derelict 225sqm site for £600,000 in 2019, and has spent a further £600,000 on the design and construction. At £1.2million, the resale value would be at the upper end for a two-bedroom house in the area, but Wilson has no intention of selling. “By any accounts that’s quite a lot, but it’s passion on my side.”
It’s not a requirement to build to Passivhaus standards or use MMC in the UK but Wilson is adamant it should be. “What we are doing here can be upscaled to major new housing developments. It is what needs to happen if we are going to meet the Government’s revised 2035 carbon reduction target, as current housing construction methods will not do so,” he says.
Some developers — most notably Urban Splash, which has created hundreds of prefabricated apartments across England — have picked up the baton but it’s the exception rather than standard. “There are a lot of building companies who are building volume houses. Those are the builders who should be doing this,” says Wilson.
“But they’ve got to be incentivised, they’ve got to be both incentivised and forced, coerced to do it through building control. There is absolutely no excuse for the building regulations, at least for residential buildings, not mandating this. It’s not rocket science, we just need to get used to it.”
More widespread use of Passivhaus-approved products and off-site methods of construction would also drive down the admittedly high price-tag of eco-consciousness. “If the whole industry was doing this, the product cost would come down and it would just become normal procedure.”
Wilson hopes to be living in his home by November, just in time to turn the heating off. By then, the wooden shell will have been clad in a combination of Thermowood and Tulipwood sympathetic to its wooded site and bracketed with plant-covered living walls, the interior fit-out complete and — all being well — a Passivhaus certification achieved.