Environmentally sound eco-homes aren’t just for architects and self-builders. They’ve just pioneered the techniques, but with every passing year, the know-how to build zero carbon buildings trickles further down through the industry. As more homes are built to high efficiency standards, the expertise spreads and the costs come down, making it easier for others to build them too.
One example is the St Mary’s development in Oldham, which was completed last year. The council bulldozed an area of sub-standard flats, and replaced them with state of the art Passivhaus dwellings. Like the last building of the week I profiled, this is social housing, managed by the housing association Contour Homes.
If you haven’t come across the term Passivhaus before, it refers to a design approach that creates houses that are so efficient that they don’t need heating. Cooking and the body heat of occupants is enough for all but the coldest of days. This is achieved by making the house airtight and packing the outer walls with insulation. The house is then ventilated through a heat exchanger that extracts warmth from the stale air being vented out, and uses it to warm the fresh air coming in.
The cost of heating one of Oldham’s passivhauses, for an entire year, is around £20 or so. By contrast, the average household spends around £13 on space heating every week.
Building these homes to this standard added £20,000 to the build cost.
The Earthbound Report 
So it takes 30 years to recoup the cost.
As the cost of heating is rising and likely to continue rising, probably less.
Anything to do with the sustainability of buildings has to be looked at over the long term, because a well built house may stand for centuries. A 30 year pay-off is no problem at all, especially when you consider the carbon savings from day one.
Since very few people own their home for 30 years from new (or even 15 years if fuel cost were to double) and they are the ones who are going to have to stump up the extra up front cost then a 30 year pay off may be a problem. Just look what happened when the government introduced the Green Deal and people had to pay back over time the cost of insulation. Even though it goes with the house and does save money in the long term take up dropped.
Time/cost of money, capital vs current spending, people’s lack of financial knowledge. These all play a part.
I forget the biggest issue: interest. £20000 at 5% is £1000 pa on top of the capital costs. Fuel prices would have to quadruple to make this cost effective.
I refer you to my opening paragraph. It used to cost £50,000 extra to build to Passivahaus standard. Like fitting solar panels, it was something you only did because you believed in it and it was the last house you were going to own. It can now be done for £20k, and the more people do it, the cheaper it will become. Eventually I might even be able to afford one.
Incidentally, if you were designing a new build, would you include central heating, double glazing, or an indoor toilet? Damn expensive, all of them.
Of course you are right that as our economy develops this stuff becomes cheaper and more affordable.
But I would fit double glazing and the like since they have direct utility. Double glazing stops drafts straight away. Passivhaus doesn’t have a noticeable effect over normal central heating in terms of how the house feels.
Possibly, though the steady temperature and indoor air quality are immediate benefits too.