Energy performance of school roofing materials in hot and humid climates

Effective roof insulation plays a pivotal role in reducing the energy used for air-conditioning, particularly in Taiwan’s extreme summer climate. In the present study, 1108 cases of rooftop insulation renovations in Taiwanese schools between 2018 and 2022 were investigated, and the thermal insulation performance and air-conditioning-related electricity savings associated with these renovations were analyzed through a cost–benefit assessment of the investment in insulation. The EnergyPlus software was used to model typical classroom roofs in seven climate zones in Taiwan. All the adopted thermal insulation methods considerably reduce air-conditioning-related electricity use; however, diminishing returns occur faster for thicker thermal insulation. The four main roof insulation materials used in the analyzed cases are galvanized corrugated steel, foam concrete, polystyrene sheets, and insulating bricks, which are associated with average maximum electricity-saving ratios of 17%, 15.3%, 10.2%, and 9.7%, respectively, and payback periods of 6.1, 6.4, 4.5, and 9.3 years, respectively. Electricity savings are greater and the payback period is shorter for the hotter southern zones of Taiwan than for the cooler northern zones. Galvanized corrugated steel has average energy efficiency of 21% and 13% in the southern and northern zones, respectively. The selection of roof construction materials strongly influences the consumption of energy for air-conditioning. Moreover, different construction costs result in distinct payback periods. The results of this study serve as a reference for school administrators and governments in the selection of insulation methods and design of building energy conservation and management, respectively.