Complying with Part L

L is for … Some building types need to shave their carbon emissions a lot. Others, less so. Yet the regulations say they all have to improve by 25%. The last in our series on Part L examines a proposal to fix this anomaly.

One of the oddities of the energy regulations is that it can be easier for an energy-guzzling air-conditioned building to comply with Part L than a naturally ventilated one. The reason is that, under the last two revisions of them, all new buildings have had to cut their carbon emissions by 25% compared with a notional model of the same building. This is obviously a lot harder to do if the type you are comparing yourself with already has low-energy credentials. The upshot is that some impeccably green buildings have failed to pass Part L, which is at best an anomaly and at worst plain daft.

Under the proposals for the 2010 revisions to Part L, rather than going for a flat 25% improvement in energy emissions for all buildings, the communities department is proposing a more flexible approach for non-domestic buildings. This would allow some to achieve less than a 25% reduction while others would be expected to cut more.
To level the playing field and make sure designers get the biggest bang for their buck, a series of cost–benefit curves will be incorporated into the notional model. This will determine the cost-effectiveness of improving elements such as lighting, windows and hot water systems relative to the overall energy performance of the building. And when the communities department carried out its cost–benefit analysis it modelled an ideal specification and came up with some potential carbon reduction targets.

So designers of types where there is room for improvement suddenly have a lot of thinking to do. Here, Building looks at which will have to make the biggest cuts, and what impact that may have on their designs.