Part L changes could increase emissions

Proposed changes to Part L include software glitches that penalise homes using recognised low-carbon technologies including biomass boilers and air-tight homes.

Services engineer Hoare Lea tested the changes in the software used to calculate compliance and found that fitting a biomass boiler added more carbon emissions than one burning fossil fuels. It also found that fitting a mechanical ventilation system which recovers heat from air expelled from homes was “severely penalised”. These systems are considered essential on low-energy, air-tight homes.

Hoare Lea also found that the software penalised displacement ventilation systems with chilled beams, and instead treated fan-coil units favourably.

This is a reversal of earlier versions of Part L. When the 2006 version was introduced, for example, there were fears that fan-coil systems would become obsolete as they were less energy efficient than displacement systems with chilled beams.

There’s a lot of work to be done and i am not sure there will be time to get it ready

David Kingstone

Concerns have also been raised over potential delays to the changes.

David Kingstone, who headed a simulation group at engineer Buro Happold that analysed the software, said there were problems with a proposed change that would allocate separate carbon reduction targets to different building types.

He said: “There’s a lot of work to be done on the software and I am not sure there will be enough time to get it ready.”

The consultation closed this week.