The continuous appearance of new materials, the general tendency towards lighter structural loads, the increased personal welfare levels, the extended use of mechanical equipments for environmental conditioning in most of the housings presently being constructed, and the incessant and considerable increase of the organic fuel costs have given rise to a new study, both in scope and precision, of the physical and construction basis of the fundamental problems of living spaces. A comparative study is here carried out of the existing national and foreign Norms on the hygrothermal requirements that the members, and the spaces they form, have to comply with, so as to obtain comfort within the budget limits of an effective economy. As already mentioned, this is the last one of three articles published in consecutive issues of INFORMES DE LA CONSTRUCCION.