Thermal mass helps to store heat within the building structure and moderate fluctuations in the indoor temperature. This heat storing capacity of building material helps in achieving thermal comfort for occupants by providing time delay. Hence, choosing appropriate building materials can largely effect the level of comfort within buildings. To meet NZEB design parameters, selection of building materials hold utmost importance in modulating indoor temperatures and hence reducing conventional energy loads.
Mass and density of a building material affects this heat storing capacity in buildings. High density materials such as concrete, bricks and stone have high thermal mass, while materials such as wood or plastics have low thermal mass. The efficacy depends on the placements of these elements with respect to direct irradiation of the sun.
Thermal mass regulates the temperature of the space by controlling the amount of thermal energy stored in the building. Heavy thermal mass buildings can keep the spaces comfortable for several hours even after the HVAC system is switched off.
Heavy thermal mass also delays the ingress of heat, and when combined with natural ventilation and night-purge strategies, can ensure that the building is pre-cooled naturally in the morning and stays cool even after the outside temperature soars.
In warm and humid climates, low thermal mass buildings eliminate heat build-up and dissipate heat quickly to the ambient.