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Part L


Conservation of Fuel and Power
Recent changes in the building regulations are being driven by the commitment for the Government to continually improve thermal performance of buildings.

The building regulations part L are subdivided into L1A (new dwellings), L1B (existing dwellings), L2A (new buildings other than dwellings) and L2B (existing buildings other than dwellings). Within each of these documents are different limiting U Values setting minimum performance requirements and the calculations methods to prove compliance.

Copies of the building regulations can be downloaded from: www.planning

Compliance Methods

Key Changes 2010
The limiting values have remained largely unchanged for the commercial market giving building designers flexibility to improve different building elements to achieve overall building targets.
The residential market has seen increases of 0.2W/mēK in the limiting value. Document L1b and L2b relate to both replacements and extensions to exiting buildings. The limiting value for refurbishment was previously lower then the value required for extension, this has been brought in line with the same value for replacement and extensions and all replacement windows should be installed with cavity closers where appropriate.

New build reduced to 2.0W/mēK (from 2.2W/mēK).
Replacement Windows 1.6W/mēK (from 1.8W/mēK) or a Rated D (from E)
Replacement doors remain at 1.8W/mēK
Domestic Windows by 0.2W/mēK or 10kWhr/mēYear.

New Build remains at 2.2W/mēK
Replacement windows and doors at remain 1.8 W/mēK
High usage entrance doors are now to be 3.5W/mēK from 6.0W/mēK.