Abstract
<jats:p>The criterion for the effectiveness of thermal insulation of a building wall is the reduction of heat loss from the wall after covering its surface with a layer of thermal insulating material. Heat loss is determined by the thickness and thermal conductivity of the wall and insulation materials, as well as the heat transfer associated with the outer surface of the wall. Heat exchange between the outer surface of the building and the surrounding environment is based on radiative and convective mechanisms. This process includes thermal radiation from the sun, heat exchange through long-wave radiation with the atmosphere, and convective exchange with the external air. Typically, less attention is paid to the effects of incident solar radiation and radiation exchange with the atmosphere than to heat transfer through the building wall caused by thermal conductivity. For calculating the thermal resistances of the outer surface of the wall related to radiation and convection, a simplified methodology proposed by relevant standards is usually employed. Under certain conditions, this can lead to significant errors in determining the heat loss of the building. On the other hand, the use of empirical dependencies to determine the apparent temperature of the atmosphere, necessary for calculating the thermal flow of long-wave radiation from the atmosphere, is unjustified. These dependencies are not universal and were obtained for specific meteorological conditions through measurements in specific locations. A modification of the calculation method for determining the effectiveness of thermal insulation of a building wall has been carried out by refining the calculation of heat transfer between the outer surface of the wall and the surrounding environment. From the thermal balance equation for the outer surface of the wall, considering the thermal flow of absorbed solar radiation and the thermal flow caused by the radiative cooling of the wall, expressions have been derived that allow for the assessment of the effectiveness of the thermal insulation of the building wall through the reduction of heat loss from the wall after covering its outer surface with a layer of thermal insulating material.</jats:p>