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Insulation and U values

Dense concrete has a large thermal mass and it is not a particularly good insulator. In winter weather conditions, the temperature differences between the interior and exterior of a structure can lead to significant heat losses unless properly insulated, airtight and efficiently designed. Retaining as much heat as possible in the structure in cold weather conditions, to reduce the environmental impacts associated with heating a building, is important. It has been estimated that 27% of the UK total CO₂ emissions are from domestic heating. It is for this reason the Building Regulations (Part L1: ´Conservation of fuel and power in dwellings´) have been changed and now require lower U-values.

U values for various building elements.

Exposed element
Pitched roof with insulation between joists.........................0.16 W/m²K
Flat roof....................................................................0.25 W/m²K
Walls including basement walls................................... ....0.35 W/m²K
Floors, including ground floors and basement floors.............0.25 W/m²K

For further information see U-values: understanding heat movement, published in CONCRETE in March 2003, pp 42–43. Copies are available as a free download from the Members Area of the Concrete Society web site.

Acknowledgement: UKQAA