An Experimental Investigation for the Influence of Glass Type on Indoor Thermal Comfort and Cooling Energy Consumption

Aligned with the sustainable development goals of affordable energy, health, and well-being, there is a growing focus on building energy efficiency and indoor environmental quality (IEQ). Solar radiation increases indoor mean radiant temperature, causing thermal discomfort for occupants near windows. To mitigate discomfort, it is inevitable to lower the indoor temperature, which may lead to increased electricity consumption. We set up test units with glass types having SHGC from 0.28 to 0.85 and also installed sensors near windows to measure the impacts of solar radiation on PMV and cooling consumption. Environmental Quality Index (EQI) serves as an indicator for assessing thermal conditions. EQI categorizes time fractions into seven levels (A to G), based on PMV categories of the thermal environment. At a set-point of 26°C, the test unit equipped with the lowest SHGC records an average daily electricity consumption of 1.23 kWh/day, with an EQI of C. In comparison, the test unit with the highest SHGC consumes 2.96 kWh/day, reflecting an EQI of G. Lower SHGC glass effectively blocks incident sunlight, resulting in reduced electricity consumption and improved indoor thermal comfort. To address discomfort stemming from high SHGC values, the set point was lowered to 24°C. Consequently, the test unit with the highest SHGC experienced an increase in EQI to E, accompanied by higher electricity consumption of 3.57 kWh/day. This study emphasizes the importance of using EQI as a unified benchmark for comparing the energy-saving potential of glasses, as temperature-based assessments may underestimate the potential of low SHGC glass.