The effect of suspended ceilings on thermal mass to reduce overheating

Thermal mass has the benefit of regulating energy in buildings and generates potential savings in energy and CO2 emissions. The effect of climate change with increasing air temperature intensifies even more the opportunities for the use of thermal mass to reduce overheating in summer and minimize the use of cooling energy, providing savings in energy and CO2 emissions. In most educational buildings, the thermal mass is hidden behind a compressed mineral wool suspended ceiling. The suspended ceiling produces a blocking effect for the use of the thermal mass to regulate the indoor conditions, avoiding the loading and unloading of the thermal mass as a regulatory mechanism for indoor temperature. The aim of this study was to investigate the impact of suspended ceilings on overheating and the benefits of using thermal mass to reduce overheating. The approach used in this study was based on dynamic thermal modeling to analyse the overheating performance of a test room with suspended ceiling and with the thermal mass exposed. The testing room was simulated under weather conditions for two locations in Europe, London in the United Kingdom and Munich in Germany. The test room was modeled and simulated using energyplus in DesignBuilder. The test room was modeled using medium weight construction in accordance with the UK Building Regulations Part L2 2010. All room surfaces were adiabatic apart from the south facing wall, which compromised 50% of glazing. The test room was naturally ventilated and a night cooling ventilation strategy was used to cool down the thermal mass. No cooling was used in the simulations to be able to quantify the benefits provided by the thermal mass to reduce overheating. An overheating limit of 28 ºC was chosen in accordance with the Building Bulletin 101 Ventilation of School Buildings to assess the performance of the thermal mass during the simulations. The simulation results show that by exposing and making use of the room thermal mass, the number of hours above 28 ºC can be reduce by at least 33% in Munich and 49% in London. The reduction in overheating hours will consequently minimise the need for cooling energy in summer providing savings in energy and CO2 emissions