The thesis deals with cost-based selection of construction materials, illustrated on the example of a single-storey house to be built in Gabarje. A bill of quantites is prepared for every thickness and type of building material. The calculation is based on the data related to the origin of material, the purchase price and the price of the material supplied to the site for the materials selected. A pro forma invoice that includes the cost of materials, labour and transport is prepared for every item. Three different load-bearing materials (cast-in-situ concrete, brick wall and foam concrete brick wall) and two different insulation materials are selected. The analysed envelope system consists of load-bearing wall and insulation layer, where the thickness of both layers is varying. All feasible envelope systems are analysed by using the software that complies to the Slovenian standard for building energy efficiency, and yields as result the building's annual heat consumption and heat resistances of the walls. The break-even analysis was carried out for all envelope systems considered. The system resulting in lowest initial (construction) cost that also meets the regulatory requirements was selected as the reference case. Three differenty types of fuel, namely wood, natural gas and oil were considered in the analysis. Assuming that the price of fuel does not change in the future, the analysis results show that the fastest return of initial investment into additional thermal insulation is achieved for the case of foam concrete brick walls.