On Sunday the Guardian ran a story revealing that government officials have accepted that the goal of making all new homes zero carbon by 2016 has to be watered down.

ENDS Report readers will know this has long been the risk. The target was established by the previous Labour government in 2006. But achieving it in any literal sense was always going to be impossible because homes depend on sources of energy generated elsewhere, at present, mostly from fossil fuels.

A more flexible definition was developed (ENDS Report, January 2009). The key issue is how much of the carbon reduction will have to be delivered by improved building design and on-site renewables, and how much can justifiably be left to off-site solutions, perhaps with house builders paying into a fund for energy efficiency projects elsewhere.

Industry representatives and government officials are thrashing this issue out in discussions at the Zero Carbon Hub, the zero-carbon homes delivery body. A recommendation is hoped for later this year.

Until now the definition had assumed that some 70% of the carbon reduction would occur at the site of the new home and the rest off-site. The Guardian suggested there is increasing pressure from house builders to reduce this threshold.

ENDS’s sources seem to confirm the picture. One industry figure said that, although there was still broad support for the zero-carbon target, there was a “spectrum of views” over the right level for the threshold.

Another industry figure told ENDS that the threshold should be reduced to 44%. “You can’t ask the house builder to do the job of the energy company,” they said. The recession has also dented house builders’ confidence that the 2016 deadline can be met (ENDS Report, November 2009).