The cost of building zero-carbon homes makes the government's ambitious housing targets impossible to achieve, a top sustainability expert has claimed.
The source, who is among the European Commission's chief advisors on sustainability, said that building zero-carbon houses could cost up to £100,000 extra per unit, casting into doubt the possibility of delivering Prime Minister Gordon Brown's target of three million new homes by 2020.
The whistleblower also labelled housing minister Yvette Cooper's target for all new houses in the UK to be zero carbon by 2016 as 'complete science fiction'.
The source said: 'By the time you've added up your shopping list of items to build a zero-carbon house, referred to as Code Level 6 in the Department of Communities and Local Government's (DCLG) Code for Sustainable Homes, you're looking at anything up to £60,000 to £100,000 extra on top of the regular building costs.'
These allegations have been substantiated by several major practices, such as Hunter & Partners, which is currently looking into building its first Code Level 6 zero-carbon homes.
The firm's head of sustainability, Tim Ashton, said: 'We are looking at a small, pilot Code Level 6 scheme at present, and this is currently being priced at around £60,000 per unit over standard comparable housing costs.'
The insider added that even if costs came down enough to make building Code Level 6 houses feasible, the building skills involved are way beyond the current level within the construction industry.
He said: 'We are not even building houses, in bulk at least, to German PassivHaus standards - which is only comparable to Code Level 4 in this country - particularly when it comes to airtightness.
'If we get to German PassivHaus standards by 2016 that would be phenomenal, but to think we can build zero-carbon houses by 2016 is complete science fiction.'
Sheppard Robson's head of sustainability, Alan Shingler, who helped design the UK's first Code Level 6 house - the Lighthouse, at certification group BRE's research site in Watford - agrees that the lack of skills is a major issue.
'There needs to be a complete shift in the construction of houses - a behavioural change. It is meeting the air-tightness parameter that will be the biggest challenge,' said Shingler.
The UK's three largest housebuilders - Persimmon, Barratt and Taylor Wimpey - declined to comment on the 2016 target, but the National House-Building Council (NHBC) was optimistic.
Robert Lockey, service training manager for the NHBC, said: 'Yes, it will be hellishly challenging, and there is a lot of work to do. But I have to say it's possible. First, we need the designers to figure out what works best. When that is decided, we can get on with training people up.'by Richard Vaughan