thermal mass is a material that absorbs heat from a heat source, and then releases it slowly. In buildings, thermal mass is provided by the structure of the building, the level of which is determined by the material the building is constructed from. Buildings constructed of lightweight materials such as steel or timber are not considered to have good thermal mass properties compared to concrete, brick and stone for the reasons that they either have low thermal conductivity performance therefore a low ability to absorb heat, or can absorb large amounts of heat but the rate of heat release is also high. Concrete, brick and stone are all materials that are able to absorb and store heat until the surface of the material is exposed to cooler conditions and its temperature begins to drop. When this happens, the stored heat transfers to the cooler surface and is released back into the building.
The ability to absorb and release heat in this way enables buildings with thermal mass to respond naturally to changing weather conditions, helping to stabilise the internal temperature and provide a largely self-regulating environment.
The role of a buildings thermal mass can be of benefit throughout the year. During the warm weather in summer, heat will be absorbed by the thermal mass in order to prevent overheating in the building, providing a more comfortable living or working environment in naturally ventilated building or in air-conditioned building, reduces the cooling demand on mechanical air-conditioning systems. Allowing cool air to ventilate the building at night allows heat that has been stored throughout the day to be removed. This daily heating and cooling cycle works particularly well in countries such as the UK where night time temperatures are typically around 10 degrees less than peak daytime temperatures, making it an effective way of drawing heat from the structure of the building. The benefits of thermal mass during winter when heating demands are at their greatest, can help to reduce fuel consumption when used in a passive solar design. In doing so, solar gains in winter, along with heat produced from appliances, cooking, people and lighting, uses the thermal mass to absorb gains which is then slowly released overnight as temperatures fall, helping to keep the building warm and reducing the need for additional heating.
However most buildings constructed past and present do not utilise the thermal mass properties of the structure due to a number of reasons such as:
◦The requirement to internally insulate buildings from heat loss and improve air tightness, preventing heat conductivity into the buildings structure.
◦Secondary linings to the internal surface of the buildings structure for aesthetical reasons, reducing the heat conductivity rate or removing any thermal mass performance where insulated panels are used.
◦The structure of the building is of lightweight construction and has little or no thermal mass qualities.
Posted Saturday 8 Dec 2012 @ 12:40:55 pm from IP
# 
