This paper attempts a new classification of insulating materials from the perspective of their utility in the pro-ecological passive construction industry. The main criterion is the conductivity of thermal and solar energy. Based on their ability to conduct or block fluxes of thermal and solar energy, six types of insulating walls are proposed. On the basis of this criterion there are traditional dividing walls (typical walls, wall insulating materials, windows), energy-saving building materials (Trombe walls, transparent insulation, energy-saving windows) and materials of the future. This classification will facilitate the conscious and planned development of the latter. These new-generation materials allow energy to be saved, but they also enable it to be harnessed from sunlight (transparent insulation) and to store it, for example, in phase change materials. Combining these materials in hybrid solutions will provide fresh opportunities for the energy-saving building industry. Theoretical research into these six types of insulating material has enabled their properties and building utility to be formulated. (C) 2013 Elsevier B.V. All rights reserved.