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Part L: wait for key information not over

Industry experts say they are still waiting for crucial information on implementing the Government’s moves to tighten building regulations.

They said they have yet to see the most crucial aspect of the Part L Approved Documents after the Government published its longawaited amendments last week.

The revisions to Part L, about the conservation of fuel and power in the building envelope, put a new emphasis on energy consumption as well as carbon emissions. But the crucial calculation methodology is still in draft form and subject to change.

David Kingstone, associate at engineering consultancy Buro Happold, said: “Although the
approved documents have been published a month later than expected, the most important document – the calculation methodology – is still subject to change.

This needs to be finalised and published so that the software can be updated and approved, and assessors are able to study the new software prior to the October launch.”

Principal consultant at sustainability consultant Inbuilt Mel Starrs said it is difficult to fully understand the impact of the changes to Part L until they get all the supplementary documentation.

She said: “Overall, I’m very happy that the Approved Documents are out, but there are a number of supplementary documents referred to which aren’t yet available.

“This included the new calculation method modelling guide, without which we can’t calculate
those all-important key figures. “The modelling guide is yet another new process for us all to grasp. Although it doesn’t appear to make much change, it’s still unfamiliar enough to unsettle us all.”

One big change will come in the way fan and pump emissions are calculated, which will mean that energy performance assessors will have to reconsider how the emissions will influence system design selection.

Although the definition for the Energy Performance Certificate (EPC) reference building has not changed, the way emissions are calculated for an actual building have. This will mean the resulting EPC rating will be different to that calculated now.

According to Mr Kingstone, this may result in a change in the EPC rating band, the number of BREEAM energy credits and even the BREEAM rating. But only by assessing this in detail, and on a range of building types, will the result be known.

Another change sees carbon emission calculations having to be submitted at the design stage, in addition to the completion stage calculation that is currently required.

With the launch of Part L’s new Domestic Building Services Compliance Guide, ventilation
performance levels are highlighted. For the first time, a specific fan power requirement of less than 0.5 W/sec is included for intermittent fans used in both refurbishment and new-build developments.