Comparison of CIBSE thermal comfort assessments with SAP overheating assessments and implications for designers

Abstract

A comparison of the overheating risk assessment of a number of residential developments shows that designs can more easily pass the Part L overheating assessment using the SAP methodology compared to the CIBSE thermal comfort assessment using dynamic modelling. There is a risk, therefore, that residences are being designed and built without an appropriate evaluation of overheating risk, if only the standard building regulation assessment procedure is used. The Part L overheating assessment is relatively simplistic, thus potentially leading to inappropriate design decisions regarding building form, materials and ventilation strategies. Dynamic modelling, on the other hand, provides a more detailed assessment and prediction of overheating risk and should be more widely used to evaluate residential designs. This work shows that, without appropriate evaluation, overheating risk in residences could increasingly become a problem. Practical application: Residential overheating risk assessments using CIBSE comfort criteria show that risk of overheating can occur in a sample of proposed residential properties, despite passing heat gain compliance checks for building regulations. Therefore, overheating assessments using dynamic thermal modelling, implemented at the planning and design stages, can provide a more appropriate assessment of thermal discomfort than Building Regulation Part L1A (criterion 3) compliance checks alone.