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DETR's Part L preview goes easy on U-value reductions

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The Department of Environment, Transport and the Regions has taken the unprecedented step of issuing interim draft Building Regulations on energy efficiency provisions to allow industry time to gear up to accommodate the changes. The revisions to Approved Document Part L, covering insulation and ventilation standards, will be published in August and will come into effect in February 2002. The AJ has obtained a copy of the document.

Elemental U-value standards for metal frame windows and wood/PVC windows have been published for the first time and will be 2.2W/m 2K and 2.0W/m 2K respectively. A pitched roof with insulation between the rafters will be 0.2W/m 2K or 0.16W/m 2K with insulation between joists; and flat roofs and floors will be 0.25W/m 2K. The full target U-value calculation method is retained.

U-values for walls in dwellings will be reduced from the current 0.45W/m 2K.This is less of a reduction than originally envisaged.

Construction minister Nick Raynsford said the hoped-for dramatic reduction to 0.3W/m 2K for walls 'would cause an undue burden on builders'.

'A key issue in the consultation on Part L was the target U-values. We have listened to the views expressed in response to the consultation and have decided to implement the changes in one stage rather than two to reduce the disruption to the industry, ' said Raynsford.

'European standards have yet to be settled.

0.35W/m 2K is still an important improvement on the current standard and we will work towards further reductions at a future date by early signalling of the prospective future target, ' said Raynsford.

The document includes 'robust construction details' on limiting thermal bridging, forcing building inspectors to pay particular attention to reducing the bridging effects between elements and around openings.

New windows, doors and rooflights, as well as the replacement of boilers and services installations, will need to comply with Part L, but maintenance items are exempted. Domestic rooflights are also likely to be exempt. The regulations now apply to existing houses rather than simply to 'material alterations and change of use'.

Trading off U-values with boiler efficiency has been removed.

For full details see the AJ on 3 May.

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