Abstract
Calculation of heat transfer in windows has a direct impact on the thermal transmittance on highly insulated glazing components. A series of experimental tests were carried out in order to calculate the U-value of active insulated windows using the Heat Flux Meter method (ISO 9869-1); this to compare the insulation properties of traditional single glass, double glazing with different aerogel fillings and vacuum glazing windows. The use of this heat flux method utilised an environmental chamber to provide a temperature difference of 15 °C reporting the U-values as follows: traditional double glazing 3.09 W/m2·K, vacuum glazing 1.12 W/m2·K, and double glazing with aerogel pillars 2.52 W/m2·K. On the other hand, double glazing with KGM wheat starch reported 3.40 W/m2·K, double glazing with granulated aerogel 2.07 W/m2·K and heat insulation solar glass 1.84 W/m2·K. Vacuum glazing recorded optimal results under these experimental conditions, describing a U-value 78 % lower when compared to traditional single glazing window units (5.15 W/m2·K). Installation of windows with lower thermal transmittance are expected to increase in the global market to meet the current construction codes, aimed for achieving net zero carbon buildings.
Highlights
Energy consumption in the construction sector has increased in recent years, as buildings account for more than 40 % of the energy consumption for most countries (IEA, 2013)
A summary of the outcomes derived from the experimental procedure is presented in Figures 6 and 7, along with the interior and exterior temperatures on the surface of the glass specimen (Tsij&Tsej); additional parameters analysed included the density heat flow rate (q) and the calculated thermal transmittance (U-value) during the 72 hour period
The reduction of gas molecules in the gap has demonstrated to have a considerable impact on the thermal transmittance of manufactured and commercial vacuum samples. These results demonstrate the high potential for vacuum glazing windows for the reduction on the heat transfer in window technologies, decreasing the overall glass thickness, and improving the thermal transmittance of the window prototypes
Summary
Energy consumption in the construction sector has increased in recent years, as buildings account for more than 40 % of the energy consumption for most countries (IEA, 2013). Windows allow bringing solar heat gain, natural light, ventilation and sound vibrations to interior spaces, and they are a barrier to inclement weather conditions. These elements are extremely important to estimate the building energy performance since they act as an envelope for thermal comfort in spaces. The assessment of the window’s thermal and optical properties utilises three parameters: visible transmittance, solar heat gain coefficient (SHGC), and thermal transmittance (or U-value) (Aguilar-Santana et al, 2020). Thermal transmittance is relevant for the analysis of insulating properties of glazing materials as per the main objective of this paper, and Figure 1 presents examples of their conventional values
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