Part L Building Regulations 2010
Approved Document L of the Building Regulations, for the conservation of fuel and power, has recently undergone a major revision, which came into force on the 1st October 2010. The overall impact of the changes will be a 25% reduction in the CO2 emissions, which is a step along the governments stated trajectory to zero carbon by 2016/2019.
One of the most significant changes is the method for calculating the target emissions rate for buildings other than dwellings. The compliance for new build will still be assessed using SBEM (or other approved software packages) against the 2010 Notional building.
How has the methodology, for demonstrating CO2 emissions compliance for new buildings other than dwellings, changed?
Part L compliance for CO2 emissions is achieved by ensuring that the actual building emission rate (BER) is less than the target emission rate (TER) which is calculated from the new 2010 Notional Building. The 2010 Notional building specification has been derived such that the weighted average CO2 reduction across the entire building stock will be 25%.
Some buildings will show significantly larger or smaller improvements when compared with a 2006 compliant building, however the actual percentage improvement against 2006 is purely academic as compliance is against the new 2010 Notional Building emission rate.
The building designer must submit the SBEM calculations to Building Control at design stage as well as on completion. Altering specifications between these stages could affect compliance.
Is using the same building specifications as the Notional Building the best way to comply with the requirements?
The specification for the Notional Building has been derived as a single specification, which will give an overall 25% reduction in CO2 emissions from the building stock. It has not been optimised for any specific building type or size and as such could be considered as the “best single compromise solution”. It does however provide the building designer with a good starting point, which can then be adjusted to suit the actual building. The building designer needs to establish the most cost effective solution to deliver the required performance.
Looking specifically at pre-finished steel building envelopes, good levels of air-tightness and thermally efficient details can provide large benefits, with relatively low cost implications. Decreasing insulated element U-values in some cases will only yield small benefits and can have knock on cost effects on the overall building structure. By specifying some aspects of the building which perform better than the Notional Building, the designer can relax other aspects, however he must ensure that all elements of the building perform above the minimum or backstop values.