Thermal properties of clay bricks
The thermal properties of a wall are related to its ability to transmit or resist the movement of heat and to its capacity to store thermal energy.
Thermal transmittance, (U value) is measured in Watts (W) per square metre (m2) per degree Celsius, W/m2 oC as the rate of heat flow through an element, e.g. a wall. The lower the U value, the better the insulation properties of the wall: it has a greater resistance to the flow of heat. The U value not only takes into account the resistance offered by the wall, but also the outside and inside surface resistance. Since the U value notionally provides a measure of the heat flow through a wall, it is the figure used to compare the performance of different constructions and to make energyuse calculations.
Thermal capacity is measured in Joules (J) per square metre (m2) per degree Celsius, J/m2 oC, and is a measure of the degree of heat that can be stored by a wall. Clay brick walls, with their high thermal capacity, have the ability to store heat during the day and release this heat at night. In climatic regions where there are high temperatures during the day and low temperatures at night, this results in thermally comfortable dwellings with a reduction in energy consumption to cool or heat the buildings.