Insulation Against External Noise

This Digest explains how the external envelope of a building (the windows, walls and roof) affects the level of noise that is transmitted from outside to inside. It depends on a number of factors: the mass of the envelope, its continuity and the extra insulation afforded by double-leaf construction. There are also certain planning measures that will minimise the exposure to outside noise. The proportion of wall area that is occupied by window glazing has an appreciable effect on the overall performance of the window/wall area unless the windows are designed to a standard that matches the wall construction. Open windows greatly reduce the overall performance. It is therefore necessary to consider the ventilation needs of buildings in noisy locations. This Digest replaces Digest 128 and 129 which are now withdrawn.