More Sustainable Masonry Façades: Preheating Ventilation Air Using a Dynamic Buffer Zone (DBZ)

During sunny conditions, surface temperatures on masonry façades can rise to over 40 degrees centigrade above the ambient temperatures. Conventional wall designs minimize the benefits of this solar heat through the use of thermal insulation. However, air that is drawn from the outdoors, between the façade and sheathing, can be used to recover heat from the masonry. The system, which utilizes a Dynamic Buffer Zone (DBZ), acts as a solar air collector. This system can provide an effective way to preheat ventilation air at little to no extra cost while not compromising the architectural features of the masonry wall system. A numerical model was developed to predict the amount of heat recovery possible using a DBZ. The numerical model was verified by comparing results with a commercial computational fluid dynamics software package and by conducting laboratory experiments. Preliminary results indicate that the DBZ as a solar air collector can achieve as high as 33% daily solar efficiency and seasonal solar efficiencies of up to 27%. Since this system is low-cost, yet effective, it may offer designers an opportunity to build more sustainable masonry wall systems.