Mandatory energy calculations

From April 2006 there has been a fundamental change to the way of dealing with energy requirements in Building Regulations in England and Wales (Scotland and Northern Ireland will follow). Roger Hitchin of the BRE explains what it means to you.....

Target emissions

Instead of having to satisfy particular values for insulation levels, lighting efficiencies and so on, it is now necessary to show that the carbon emissions of the building as a whole are below a particular level. This means doing an energy calculation.

For housing the calculation is a new version of the Standard Assessment Procedure SAP, so the procedure is not too different from what we have been used to.

For non-domestic buildings (and a few large dwellings), new procedures are used. The simplest of these is the Simplified Building Energy Model SBEM. This is intended to be able to deal with most buildings and can be downloaded from www.ncm.bre.co.uk , together with the user interface iSBEM and a User Guide. Some commercial software companies will also include SBEM as part of their product package. Other software – for example, energy simulation programs – may also be used, provided that it has been accredited as suitable by ODPM.

The calculations take account of the efficiency of heating, lighting and cooling systems as well as the provision of day-lighting and the insulation and air-tightness of the building. The target emissions value for a building is determined by calculating the emissions of a “notional building” of the same size, shape, use and weather as the proposed building but with standard values for insulation, heating efficiencies etc. This is then reduced by a factor defined in the Regulations to set the target. (All the notional building calculations are carried out automatically by the software.)

There are still minimum values for insulation, boiler efficiency etc but, in themselves, these will not produce a compliant building.

These changes have been introduced so that the UK will comply with the European Energy Performance of Buildings Directive. Other measures will be introduced to comply with further requirements of the Directive: notably “energy labelling” (strictly speaking “Energy Performance Certification” of both new buildings and existing ones (when they are sold or let). This provides a means of identifying new buildings that significantly outperform the Building Regulations requirements. It also enables purchasers or renters to compare the energy efficiency of new and old buildings.

Further information

Building Performance Directive Implementation Advisory Group (DIAG): www.diag.org.uk
DEFRA: www.defra.gov.uk/ENVIRONMENT/energy/internat/ecbuildings.htm
European Alliance of Companies for Energy Efficiency in Buildings (EuroACE): www.euroace.org/bdirective.htm