The object of this Digest is to summarise the principal information which is available and to outline a method for determining the most suitable measures to be adopted for restricting the rate at which heat is lost from dwellings. The method given has been developed from a study of typical local authority dwellings and may be used where it is desired to compare the merits of different standards of insulation for the ground floor, external walls, and roof structure of such dwellings, including flats, semi detached, detached or terrace houses.