Thermal Evaluation of a Water to Air Heat Exchanger Combined with Different Roof Configurations for Passive Cooling

Traditional conservation strategies often prioritize minimizing water use; nevertheless, water can also enhance thermal comfort by incorporating a water to air heat exchanger (WAHE) alongside non-direct evaporative and radiant cooling techniques. A WAHE can be installed in features such as ponds, water tanks, or rainwater cisterns. This article assesses the cooling potential of two prototypes of roof ponds and a green roof connected to WAHE. Several testing units measuring 1.35 x 1.35 x 1.35 meters with identical heat characteristics, excluding the roof, were constructed and tested. In the first system, the heat that the green roof could not absorb was transferred to a water reservoir and then dissipated to the outside. The first roof pond prototype features a 0.35 cm deep water pond topped with a 0.03m thick insulating panel and a spray system. The second roof pond variant has an aluminum sheet with a 0.10m air gap above a 0.25m deep water pond. Several test series were conducted over a year, and a comparison was made with a baseline unit that meet California's energy code standards. The results suggest that combining a WAHE with different roof configurations offers promising benefits while keeping water consumption limited.