Modelling software for Part L
Ahead of the Part L Conference, BRE’s Paul Davidson explains how dedicated software can help tackle the stricter targets set by the new Part L.
Ever since Part L was revised in 2006, the only way to demonstrate compliance for a new building has been to calculate its overall energy performance and to compare the resulting CO2 emissions with a target value.
As buildings move closer to a zero-carbon goal, the interaction between fabric and services becomes ever more critical. The revision to Part L, which came into force on October 1 this year, maintains the same underlying methodology, though the targets have been tightened up to deliver energy improvements of 25%.
The calculation is performed using dedicated software tools, two of which have been developed for the government by the Building Research Establishment. For dwellings, the Standard Assessment Procedure is the only acceptable option, though different software suppliers have their own versions, approved by the Communities & Local Government department for this purpose. The latest version of the specification – SAP2009 – allows features such as thermal mass and some innovative heating and ventilation technologies to be properly accounted for in dwellings with low energy demands.
For all other buildings, the default software is the Simplified Building Energy Model. The latest version of this – v4.1.a – is available from www.2010ncm.bre.co.uk.
For more complex buildings, especially those that need sophisticated models to help design some of their features, approved simulation software can be used to demonstrate compliance. Recent improvements to SBEM have reduced the variability between its results and those delivered by the other tools.
Although neither SAP nor SBEM should be used as design tools, in the sense of confirming that a particular solution will work in practice, or sizing its components, they can assist in the design process. SBEM, for example, provides diagnostic information on the different uses of energy within the building, and therefore where improvements might be sought to achieve compliance with the target.
Paul Davidson is director of Sustainable Energy, BRE and will be aking part in the Part L Conference on December 14