Effect of high-performance facades on heating/cooling loads in London, UK office buildings

Office buildings require a significant amount of energy for heating and cooling purposes. A possible strategy for reducing this energy in order to reduce carbon dioxide emissions and operational costs is to specify high-performance facades. However, their benefits remain unclear for UK conditions with mild winters and cool summers. This paper reports on an investigation on the energy demand of offices in London, UK, incorporating facades with U-values between 1·2 and 2·6 W/(m² K) and g-values between 0·3 and 0·5 using the dynamic simulation tool Tas. Other variables considered included climate change (using the Chartered Institution of Building Services Engineers’ future weather data files), low internal gains, long working hours and office orientation. It was found that, apart from the case when internal gains are low, cooling is overwhelmingly necessary and energy usage increases with decreasing U-value and decreases with decreasing g-value. Low-U-value facades act to reduce conduction heat losses, thereby increasing energy use. Conversely, low-g-value facades act to reduce solar heat gains, thereby reducing the energy required for cooling. The results are used to highlight deficiencies in The Building Regulations 2010 and where more advice would be of benefit. The paper also discusses the merits of a number of strategies for reducing energy use in office buildings.