Field Experimental Study of the Effect of Cool Roof Coating on Indoor Air Temperature in a Typical Concrete Building in Hadhramout, Yemen

Abstract

Roof heat gain is a crucial factor in determining a buildings thermal performance. However, strategies aimed at minimizing this heat gain—both during construction and in post-construction retrofitting—are frequently limited or inadequately addressed. This study examines the effect of a cool roof coating on the indoor thermal conditions of a typical concrete residential building located in Hadhramout, Yemen. Despite the growing global interest in passive cooling technologies, no prior research has evaluated the effectiveness of cool roof coatings in this specific regional and climatic context, nor has the extent of indoor air temperature reduction resulting from such an intervention been empirically established. In-situ measurements were conducted through a field survey involving two adjacent rooms of identical design, condition and specifications. The measured parameters included indoor and ambient air temperatures, in addition to indoor and outdoor roof surface temperatures, both before and after the application of the cool roof coating. Data were collected during the peak thermal stress months of July and August. The results revealed that the application of the cool roof coating led to a decrease in indoor air temperature ranging from 0.1°C to 2.4°C. Moreover, indoor surface temperatures decreased by approximately 1.2°C to 5.4°C, while the outdoor roof surface temperature exhibited a marked reduction of up to 15.9°C at midday. These findings provide empirical evidence supporting the efficacy of cool roof coatings as a viable passive cooling strategy for improving indoor thermal condition in concrete buildings situated in hot-humid climates.