Assessment of the Effect of Energy Saving and Heat Loss Through External Enclosure Structures with Low Resistance to Air Penetration

Abstract

The features of heat and mass transfer through external enclosure structures with capillary - porous material, which are not taken into account in the norms of thermal protection of buildings, are considered. Such features more often occur in buildings with a long service life because of the increasing heat loss, caused by the violation of the terms of repair for a long time. For structures, located in the lower part of the building and having little resistance to air penetration, a calculation model is considered to determine the value of the economizer effect and the saving of thermal energy in conditions of cold air infiltration. The developed model clearly demonstrates, that for two - and twelve-story houses the saving of thermal energy, as a result of the economizer effect, is about 3% and 10% respectively. A computational model of exfiltration of warm air through similar structures, located in the upper part of the building, is proposed. An additional value of heat loss during exfiltration of the warm air from the rooms is determined, using an example of old building with a wooden floor of a cold attic and bulk insulation in the absence of layers with high resistance to air penetration. This value is 3.5 times higher, then that determined by the standard method, which does not take into account the redistribution of cold and warm air densities along the height of the building. This leads to a deterioration of the indoor climate and an increase in heat loss. By calculation, the dependence of the value of heat losses on the total thermal resistance of the attic floor and on the number of floors was established. A number of measures, aimed at improving the energy efficiency of existing residential buildings, are proposed, such as laying a vapor barrier layer and an additional layer of effective thermal insulation on top of the bulk insulation as part of the attic floor and installing a cement-sand screed for this insulation.