Thermal comfort of a radiant cooling system in glass fiber reinforced gypsum roof – An experimental study

Abstract

• Thermal comfort is achieved in a low embodied energy building with low energy cooling. • A high supply water temperature of 20 °C provided thermal comfort in a warm climate. • Radiant cooling of all surfaces provided thermal comfort even in hot weather. • Regression equations are developed to quantify the comfort in similar structure. • Air cavities in glass fiber reinforced gypsum roofs reduce penetration of solar heat. A holistic energy conservation approach that reduces the operational and embodied energy of the building is the need of the hour. A novel system that integrates the energy-efficient thermally activated building system (TABS) with the eco-friendly glass fibre reinforced gypsum (GFRG) reduces both operational and embodied energies. This system is termed a thermally activated glass fibre reinforced gypsum (TAGFRG) system, and research publications on this novel system are scarce. TAGFRG system is in the development stage; hence, its thermal comfort performance must be investigated extensively. A good understanding of the influence of operating parameters of the TAGFRG system can help in achieving the required thermal comfort by controlling these parameters. Therefore, the influences of supply water temperature and cooling surfaces are investigated experimentally and quantified using Fanger and adaptive thermal comfort models. An experiment room (3.46 m × 3.46 m × 3.46 m) with a TAGFRG roof in a warm and humid climate is used for this study. The proposed system can achieve 90% thermal comfort throughout the day, even at a high supply water temperature of 18 and 20 °C. An increase in supply water temperature from 18 to 26 °C increases the diurnal average operative temperature from 24.1 to 26.1 °C. An increase in the cooling surface area increases the cooling output and improves thermal comfort. The average predicted percentage dissatisfied is 22% if the roof alone is cooled directly with TABS. It reduces to 6% if all surfaces are cooled. The regression equations developed can quantify the thermal comfort indices for buildings with similar conditions at various water temperatures.