Materials and retro-fit methods for reducing rates of heat loss through walls

Retro-fitting thermal insulation to walls has become popular, both as a [`]standalone' measure and as an integral part of building-refurbishment schemes. The benefits and disadvantages of fitting thermal insulants, either on the room side of the inner leaf, or to the [`]weather-side' of the outer leaf, or within the cavity of the exterior walls of buildings, are discussed. The effective thermal conductivities for a range of dry building materials are considered, and a [`]rule-of-thumb' equation deduced, for predicting approximately (to ±6%) the magnitude of the thermal conductivity of a dry insulating material from a knowledge of its density. Once the building is well-insulated thermally, an improvement in the effectiveness of the space-heating controls can usually further increase significantly the fuel-savings achievable, but the achievement of adequate thermal insulation should usually be the higher priority.