Review of the experimental methods for evaluation of windows' solar heat gain coefficient: From standardized tests to new possibilities

One of the most important properties of a glazing system is the solar heat gain coefficient (SHGC, or g-value) which quantifies the passive solar thermal gains. There are several standardized numerical methods of deter-mining a window's g-value. However, the methods do not consider the glazing systems in real boundary con-ditions, and usually are subjected to assumptions and empirical parameters regarding the thermal/optical behavior of the system, and the rate of ventilation of the gap between the glazing unit and the shading device which would result in under-or over-estimation of the results. For this reason, several experimental methods for investigating the g-value of windows have been developed to be used either alone or as a supplementary method for the validation purpose. This review aims to analyze the main experimental methods for assessing the g-value of windows that have been published as international standards or as scientific papers while taking into consideration the condition of experiment (laboratory or in-situ) and the part of the window which was tested (the glazing part or the entire window). The methods reviewed here include standardized numerical methods based on spectrophotometric measurements, solar calorimetric methods, non-calorimetric and in-situ methods. This review set out to give insights into the procedure, the necessary equipment units, the advantages and disadvantages, new possibilities, and the gaps associated with each method. At the end the authors proposed an approach for comparing the reviewed methods more precisely and confidently, and for investigating the reli-ability of in-situ methods.

Automated summary

The solar heat gain coefficient (SHGC, or g-value) is an important property of a glazing system that quantifies the passive solar thermal gains. Existing standardized numerical methods for determining g-values do not take into account real boundary conditions and often rely on assumptions and empirical parameters, leading to potential under- or over-estimation. Therefore, various experimental methods have been developed to assess g-values of windows, either individually or as supplementary methods. This review provides an analysis of these methods, considering the experimental conditions (laboratory or in-situ) and the tested window components (glazing part or entire window), and also proposes an approach for more precise and confident comparison of the reviewed methods and investigation of in-situ method reliability.