SBEM – limited benefit for modern buildings

Prior to the introduction of SBEM (Simplified Building Energy Model), Part L of the Building Regulations relied largely on the setting of minimum fabric insulation requirements to reduce heat losses from buildings during the heating season. As consecutive revisions of Part L were introduced, insulation levels increased, and later air permeability targets were introduced. As fabric elemental performance increased, other aspects of design such as solar gains and system efficiencies became dominant in defining building energy performance, writes Chris Croly, Building Services Engineering Director, BDP (inset).

SBEM was introduced to capture some of the more complex interactions between heat gains and losses from the building fabric. SBEM also allowed the energy implications of basic system selection and design to be considered. The method attempted to introduce some flexibility in design by comparing the performance of a proposed building with that of a reference building with fixed fabric properties applied.

While it was a useful tool for expanding the scope of Part L, it is also of limited benefit in accurately assessing the environmental performance of the next generation of buildings. A further refinement of SBEM targets is likely to be ineffective as the method is not designed to assess the modern techniques that are required to further improve building performance. The method has a number of well-established limitations and these are as follows:

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