What is thermal mass?


The key reason that heavyweight floors and walls continue to provide a benefit to occupant comfort across the day is because they can absorb a significant amount of heat with only a small increase in the temperature. This ensures a relatively low surface temperature is maintained that provides a beneficial radiant cooling effect for the occupants across the day. At night, heavyweight buildings can be ventilated using the comparatively cool night air to purge heat from the fabric so it is ready to repeat the heating and cooling cycle the following day.

亚搏娱乐网站在冬季,也可以使用热量来通过被动太阳能设计提高织物能效。有关此应用程序和热量质量的更多信息,请参见:亚搏娱乐网站Thermal Mass Explained

What properties are needed to provide thermal mass?

For a material to provide a useful level of thermal mass a combination of three basic characteristics is required:

  1. A high specific heat capacity; so the heat squeezed into every kilogram is maximised.
  2. A high density; the heavier the material, the more heat it can store by volume.
  3. 中等导电率;因此,与建筑物的每日加热和冷却周期相对于材料的速率热流入和流出。




建筑法规的部分及其相关合规工具(SAP&SBEM)使用k-values(kJ/m)来说明热量亚搏娱乐网站2K), which provides a basic indication of the thermal capacity per square metre of floor or wall. Lightweight walls have a low k-value of around 10 kJ/m2K, whilst for heavyweight walls it can be up to 230 kJ/m2K. Some generic k-values for various types of construction are published in Table 1e of SAP 10.2, whilst more comprehensive values for concrete and masonry constructions can be found in:Thermal Performance: Part L1A 2013。另外,可以使用自由来计算定制的k值和其他相关信息亚搏娱乐网站Thermal Properties Calculatorproduced by Arup in partnership with The Concrete Centre.

承认tance values

Describing a material or construction as having high, medium or low thermal mass gives a useful indication of its ability to store heat, as does its k-value. But, in order to get a better idea of how effective it is likely to be in practice, there are a couple of other important factors that need to be considered. These are firstly the length of time available to get heat in and out of the material, which is typically assumed to be 24 hours, and secondly, the rate of heat flow to and from the material. These factors are accounted for in admittance values, which provide a more detailed means of assessing the approximate in-use thermal mass performance of walls and floors, making it a more sophisticated metric than the k-value. For more information on admittance values see:亚搏娱乐网站热量解释了。


承认tance values and k-values relate to the absorption of heat inside buildings, which is the most important use of thermal mass. There is however another thermal mass related property called decrement, which can influence summertime performance to some extent. Decrement describes the way in which the density, heat capacity and thermal conductivity of an external wall (for example), can slow the passage of heat from the sun as it passes from the outside to the inner surface of the wall (decrement delay), and also reduce those gains as they pass through it (decrement factor). For more information see:Thermal Mass Explainedand for a comprehensive range of decrement values for concrete and masonry walls see:Thermal Performance: Part L1A 2013

Does thermal mass have any disadvantages?

In summer, thermal mass is only beneficial if night-time ventilation (or some other means of cooling) can be used to remove the heat absorbed by the building fabric during the day. The provision of adequate ventilation can be challenging in some environments, particularly urban locations. However, the recently introduced Part O of the Building Regulations includes provisions to ensure measures that tackle overheating in new homes are practical and take adequate account of any related noise, pollution, security and safety issues.


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