Here’s one we made earlier

Could prefabs help solve the UK’s housing shortage – and deliver on the quest for sustainable homes?

'Prefab’ is a funny word.

It’s hard to shake off the image of temporary homes built during the Second World War, or ready-made houses trucked from one state to another across the USA. But in countries like Sweden prefabricated housing represents something very different – highly insulated, energy-efficient, low-waste buildings that are cheap and easy to construct. It’s these Nordic homes that have inspired a new generation of modular eco-houses that Skanska is introducing to the UK.

Low-cost and low-energy, Skanska’s prefabricated model is known as ‘ModernaHus’. They’ve already built lots in Scandinavia, and they’re in active discussions with developers and social landlords about bringing them to the UK.

So what’s so exciting about these homes? For a start, the fact that they use 60% less energy than conventional houses. They’re engineered to meet the Code for Sustainable Homes’ Rating Level Three (the top level being six) as standard, with the option to upscale. And they’re expected to perform 35% better on energy than building regulations. Originally designed for the Scandinavian climate with its sub-zero winters, the homes incorporate triple glazing and super-insulated walls, so their thermal performance is very high. Each house also has a super-efficient ‘whole building ventilation system’, a common principle in Scandinavia, to provide fresh air with little energy use. A heat exchanger unit extracts warmth from the stale air expelled out of the kitchen and bathroom and feeds it back into the heating system.

As well as offering home owners savings on running costs, the houses themselves aren’t likely to be priced out of most buyers’ range, as many eco-homes currently are. “By designing sustainability in, rather than bolting it on, we can keep costs down,” explains David Fison, chief executive of Skanska UK. It’s also the off-site construction methods that mean building costs about 15% lower than comparable green homes. By prefabricating the structure – frame, walls and windows – and bathroom elements, the company can control waste and can build houses twice as fast. “We’ve applied principles from the motor industry, sharing common components across different housing layouts,” explains Fison.

“Our dream is to turn a construction site into an assembly site. A site where hammers aren’t necessary; everything fits right first time, every time and that’s it,” he says.

So far, Skanska has focussed on apartments, as these represent 49% of the market in the UK, but even then the components can be used to create different configurations. For example layouts can incorporate external stairwells or be built in a mansion style with central access leading off into up to six apartments per floor. This means that ‘pepper-potting’ – sprinkling poorer people throughout a community in the name of better social cohesion – is possible too, says Fison. The company is also looking at the possibility of creating individual two- and three-storey houses and incorporating ground floor retail or basement car parks, which would work in high-density urban areas.

While the idea of inhabitants altering the size and lay out of their ‘modular’ house as their circumstances change may still be a vision [read about Forum for the Future’s ‘Reef Living’ concept in GF66], Skanska has designed the ModernaHus with the future in mind. The units can be dismantled and ‘recycled’ when they come to the end of their useful life.

Although the model isn’t on the market yet, the high-speed, low-energy house should go some way into making up the 40,000 shortfall in homes built each year in this country. Not to mention taking the UK one step closer to creating the sustainable homes it has promised to build over the next decade.

Skanska is a Forum for the Future partner.

6 January 2008

Jo Reeves