Agata Anna Swierc, Henryk Foit

Sensitivity analysis of the proposed method for determining dynamic heat flux lost through the building envelope

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Abstract

Energy consumption of the building depends on transmission heat loss through the building envelope and ventilation heat loss, gains from solar radiation and internal gains such as from people or household appliances, as well as the efficiency of HVAC system. To evaluate the energy performance of building, it is necessary to collect all the available information about building construction and installations. The focus of this study was on transmission heat losses. For determination of the building energy load in dynamic conditions, the new method was proposed, which makes use of modified external air temperature. In order to calculate this temperature, the Exodus method (modification of the Monte Carlo method) was used, to obtain the dynamic heat flux which penetrates the building envelope. Based on the chosen method, authors developed their own computation procedure. It gives full access to source code and unrestricted (in terms of research objectives) structure of the model. The program calculates the dynamic heat flux penetrating multilayer walls used in the centraleastern Europe. This paper presents the sensitivity analysis of heat fluxes on a group of selected factors. The effect on the heat flux lost through the building envelope was studied for such factors as: wall orientation, layer thickness variation and changes in the physical properties of the individual layers. The variability in heat flux, which depends on the wind speed and solar radiation, and therefore the heat transfer coefficient on the external building surface was also examined.

Keywords: heat loss; transmission heat transfer coefficient; energy consumption measurements; thermal diagnostics of buildings.