External constructions of buildings provide their protection from external influences. These constructions ought to create optimal comfort of interior environment in winter as well as in summer. It has been shown in practice that the largest number of breakdowns occurs in external constructions. The external constructions of walls, roofs and floors too present a big area of problems in design of new and reconstructed buildings respectively. Heat losses of buildings through external constructions - roof, external walls, floor on the ground - are not negligible. It is therefore important to pay more attention to these constructions. Basementless buildings stepped directly on the ground are in direct interaction with subgrade and its thermal state. An amount of heat primarily destined for creation of thermal comfort in the interior escapes from foundational construction and floor on the ground to the cooler subgrade. The outgoing heat represents heat losses, which unfavourably affect the overall energetic effectiveness of the building. The heat losses represent approximately 15 to 20% of the overall heat losses of the building. This number is a clear antecedent of need for isolation and minimalization of heat flow from the building to the subgrade.