Insulation to historic homes

In historic homes it is not usually possible to achieve the ideal of a uniform level of insulation around the building. This means that there are likely to be gaps known as ‘thermal bridges’. There are advantages and disadvantages associated with particular insulation materials. Some (and particularly organic insulation materials) allow moisture to escape, but greater thicknesses may be required to achieve the same thermal performance as modern, man made, high performance insulation materials.

The Energy Saving Trust promotes levels well above those of the current building regulations. The target U-values for refurbishment (W/m2K), where appropriate, are:

Roof 0.16

Walls 0.30

Windows British Fenestration Rating Council

(BFRC) rating in band C

Floors 0.20-0.25

U-values are a measure of thermal performance – the lower the better. Although these appear complicated, they are well understood and routinely used by designers. Full details of the Energy Saving Trust refurbishment standards are given in CE83/GPG155 (see back page).