Sustainable reflective triple glazing design strategies: Spectral characteristics, air-conditioning cost savings, daylight factors, and payback periods

Buildings with conventional glazing systems are responsible for excessive cooling and heating costs. Sustainable use of energy in building environments requires the use of high-performing opaque and windowed walls. Triple glazing units attenuate solar heat gain/loss compared to single- and double-glazing assemblies, thus reducing airconditioning costs and greenhouse gas emissions. The optical, energy, economic and environmental performances of a glazing unit are strictly correlated with each other. An improvement of optical properties leads to higher glazing energy performance, cost savings, and greenhouse gas emission mitigations. This work aims to suggest and define an energy-efficient triple glazing unit for lowering cooling and heating costs in buildings while experimentally testing the spectral performance of reflective glasses and assessing heat gains/losses. In this regard, bronze, green, grey, sapphire blue, and gold reflective glasses were considered and settled in sixty different triple glazing combinations. Spectral characteristics of reflective glasses were measured experimentally using a spectrophotometer over the entire solar spectral range (300-2500 nm). For the aims of this investigation, a numerical model was developed to assess the net annual cost saving ($/m(2)) and the payback period of the examined glazing units for the eight cardinal directions (N, N-E, E, S-E, S, S-W, W and N-W). The results confirmed that the TWG35 window glass unit in the S-E orientation was the most energy-efficient glazing in terms of alleviating this critical challenge (air-conditioning cost-saving 16.72 $/m(2) among all other studied window glass units), while a payback period of 2.2 years was revealed. On the other hand, the TWG33 window glass unit has led to the optimal-lowest payback period (2.1 years), with a net annual cost saving of 16.55 $/m(2). The findings of this paper demonstrate the significance of triple-glazing design approaches from an economic and environmental point of view.

Automated summary

This study aims to propose an energy-efficient triple glazing unit for reducing cooling and heating costs in buildings, while experimentally testing the spectral performance of reflective glasses. The results indicate that the TWG35 window glass unit in the S-E orientation is the most energy-efficient glazing in alleviating this critical challenge, with an air-conditioning cost-saving of 16.72 $/m(2) among all other studied window glass units, while the TWG33 window glass unit has the optimal-lowest payback period (2.1 years) with a net annual cost saving of 16.55 $/m(2).