The significance of occupancy profiles in determining post retrofit indoor thermal comfort, overheating risk and building energy performance

Recently, retrofit of tower blocks has gained momentum particularly in the UK social housing sector due to the increasing rate of fuel poverty coupled with deteriorating indoor living conditions. However, the process of making improvements to the thermal performance of building envelopes can significantly impact on occupants’ thermal comfort, increasing overheating risks with the changing climate and associated heat waves. The first phase of the study evaluated the building energy performance of a 1960s social housing tower block prototype in London, pre-retrofit, where the building simulation model was created and calibrated with monitored indoor data and occupants’ interviews. The second research phase, the subject of this paper, uses the model to further investigate the impact of improved thermal insulation of the building envelope, based on U-values prescribed by the UK Building Regulations (Part L1B), on the potential risk of overheating. The study investigates the impact of retrofitting on occupants’ thermal comfort and building energy performance in the current and future climate scenarios (2030, 2050 and 2080). Results confirm that improving the U-value of external walls will significantly reduce the heating energy use by 70% under future climate scenarios while the Tₒ increases by 15-17% with U-value of 0.5 W/m²K and 0.3 W/m²K in comparison to the base case. The overall results indicate that the different occupancy patterns adopted in the simulation model have a significant impact on the predicted duration of overheating which will, in turn, have an impact on determining appropriate retrofit strategies to reduce overheating risks.