Optimal Thickness of the Heat Insulation Layer for the External Walls

The paper presents the methodology for calculating the heat energy losses via external walls of apartment building before and after additional heat insulation of the facades using mineral wool insulation. Normally, a higher level of thermal insulation of external enclosing structures is provided by a greater thickness of the thermal insulation layer. Additional insulation thickness requires additional investment. The higher the level of thermal insulation of external walling, the less heat is lost through the walls. Therefore, energy saving measures should be considered not only from a technical point of view, but also from an economic point of view. Based on the known parameters of the duration of heating period, investments for additional insulation of the facades in the considered apartment building and values of the operating costs for heating before and after the facades insulation, an estimation of the predicted payback period was evaluated for various thickness of the additional thermal insulation layer (50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300 and 350 mm). For the considered object an optimal thickness of the additional heat insulation layer is calculated. For that optimal thickness, payback period, calculated with account for heating energy tariffs growth rates and discounted future cash flows, takes its minimal value.