Abstract
In the design of high-energy performance buildings with ventilated facade systems, the evaluation of point thermal bridges is complicated and is often ignored in practice. This paper analyzes the relationship between the point thermal bridges resulting from aluminum fasteners, which are used for installation facades cladding, and the thermal properties of materials that are used in external walls layers and dimension of layers. Research has shown that the influence of the point thermal bridges on the U-value of the entire wall may achieve an average of up to 30% regarding thermal properties of materials of the external wall layers and the dimension of layers. With the increase in thermal conductivity of the bearing layer material and the thickness of the thermal insulation layer, the point thermal transmittance χ-value increased. For this reason, the U-value of the entire wall may increase by up to 35%. With the increase of the thickness of the bearing layer and thermal conductivity value of thermal insulation layer, the point thermal transmittance χ-value decreased by up to 28%. A simplified methodology is presented for the evaluation of point thermal bridges based on the thermal and geometrical properties of external wall layers.
Highlights
In the design of high-energy performance buildings according to Passive House standards, it is necessary to identify and evaluate the factors that increase a building’s energy losses
A 3-D temperature field simulation was done in order It is dashto determine the influence of the point thermal bridge on the behavior of the heat flow in the external wall of the building
According to the results (Figure 12), it can be stated that the influence of the point thermal bridges on the U-value of the entire wall may achieve an average of 30%
Summary
In the design of high-energy performance buildings according to Passive House standards, it is necessary to identify and evaluate the factors that increase a building’s energy losses. Because the air flow must be carefully considered and assessed, energy consumption should be below 15 kWh/m2/year One such factor is the thermal bridge, where the thermal resistance of the building envelope is significantly changed by full or partial penetration of the building envelope by materials with a different thermal conductivity, and/or a change in thickness of the fabric, and/or a difference between the internal and external areas, such as occurs at wall/floor/ceiling junctions [1]. Ascione [4] learned that thermal bridges can increase the heating demand of buildings by over 20%. Linear thermal bridges, which occur at the junction between two or more elements of the building envelope, are evaluated in the calculations of the building energy demand. Sierra [15] used a 2D model to assess thermal bridges, because they occur around windows
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