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Adjusting to Part L changes

In April this year significant changes were made to Part L1 of the Building regulations. This short blog focuses on Part L1A (newly constructed dwellings).

Energy Performance Certificate rating scale

As well as assessing the dwelling emission rate, under new regulations more focus is being made on the fabric efficiency of new homes. This approach prevents poor fabric performance being offset with renewable technologies i.e. solar/PV panels, FGHR, MVHR etc.

Due to the above two calculations are now created, one being a DER (Dwelling Emission Rate) and a DFEE (Dwelling Fabric Energy Efficiency). The inclusion of the latter means the target u-values that were previously acceptable need much improvement. The table below highlights the reference values for a notional dwelling as set out in Table 4 of the Building Regulations:

Opening AreasSame as actual up to 25% of floor area
External Wall (W/m2K)0.18
Party Walls (W/m2K)0
Floor (W/m2K)0.13
Roof (W/m2K)0.13
Windows (W/m2K)1.4
Air Tightness (m3/hm2)5
Non-Repeating Thermal BridgingStandard psi values from Appendix R of FSAP 2012, or y-value= 0.05 if 0.15 is being claimed
Ventilation TypeNatural (with extracts)
Gas Boiler89.5% SEDBUK efficiency

To assist designers with the changes Aldrock has been providing preliminary advice and specifications.  Advising on materials, insulation and construction to ensure standards are met even before design stage. This cuts down on time and ultimately cost as the project progresses.

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Energy Performance Certificate rating scale
  • 17th December 2014