How to locate thermal mass
Thermal mass needs to be situated correctly and needs to work in combination with passive solar design and good performing insulation, otherwise it can have negative effects and even increase the need for heating and cooling. Thermal mass should be situated on the interior face of the building envelope and must be thermally separated from the outside via insulative materials.
Thermal mass should be located throughout the building to maintain comfort in summer, but the main focus should be on north-facing rooms. Good solar access is obligatory as the low winter sun needs to be able to enter the building and to strike the thermal mass. The more glass area, the more thermal mass is required.
Thermal mass is extremely important for multi-storey buildings, as warm air rises and therefore the rooms tend to overheat easily. Unfortunately most upper storeys are usually built in lightweight construction, as this is cheaper and easier to build. It is important, however, to incorporate as much thermal mass as possible, for example concrete floors or internal brick walls.
When using thermal mass in upper storey buildings careful attention has to be paid on the details. For instance that there are no structural thermal bridges, which can lead to unwanted heat transfer between the outside and the upper level concrete floors. But also the floors itself need to be insulated, to avoid heat rising up and heating up the upper levels. Insulating concrete floors isn’t a legal requirements, but highly recommended, if you do want to enjoy the thermal benefits and not the negative side effects of thermal mass.
In our next article we will speak about material and colour selections.