Concrete @ your Fingertips

In-service environmental performance - housing

In UK domestic buildings, about 65% of the total energy used is in space heating, followed by 22% for hot water. The remainder is used for cooking, lighting, appliances, etc. Consequently, the main operational cost is heating. This is determined by the building envelope and orientation, ventilation rate, window type and area, and climate.

The energy used in space heating over a month depends on the average interior temperature during that period and the insulation levels (U-values) of the various structural components. Minimum U-values are specified in the UK Building Regulations; concrete, whether plain, foamed, in block form or in combination with, for example, insulating cavity fill, can easily fulfil or surpass recommended U-values.

The use of concrete in a building can affect the response of the interior temperature to the extremes of external temperatures. Its high heat capacity acts as a temperature stabiliser, preventing sudden temperature fluctuations caused by heat loads from occupants, solar gain, electrical equipment and lighting. For example, a house with concrete block walls for the outer leaf, insulation in the cavity, and concrete blocks for the inner leaf will have a high thermal capacity.

When the interior heating is off, the inside temperatures will be sustained by heat stored in the inner leaves of the walls and other concrete elements within the envelope. In summer, the walls will absorb heat from the interior space caused by solar radiation through windows, and limit temperature rise.

For further information see Concrete and the Environment, published in CONCRETE in September 2001, pp3946. Copies are available as a free download from the Members Area of the Concrete Society web site.

Acknowledgement: The Concrete Society