Optimal thickness of various insulation materials for different temperature conditions and heat sources in terms of economic aspect

The article presents the methodology for calculating the optimal insulation thickness that is related to the quality of energy supply and fuel prices. Assuming that the total cost following renovation is the sum of the costs of heating and thermal upgrading, it was shown that when calculating the optimal insulation thickness, the thermal resistance of the outer walls should be taken into account. Such calculations, in addition to the characteristics of the heat source, should be carried out taking into account local weather conditions. The study presents the results of such calculations for the building heated with gas and the air-source heat pump. The results of the investigations are referred to the mean climatic conditions recorded in the last 10 years. It was found that for thermal upgrading with the use of foamed polystyrene having the optimum thickness, total investment costs are almost the same, regardless of polystyrene thermal properties. The same also refers to energy costs. The article also provides sample calculations for plaster, the main ingredient of which is perlite. In the case of internal thermal upgrading of the historic buildings, such isolation is recommended in order to prevent moisture problems inside the envelope.