The proven adverse environmental and energy impact of mechanical cooling globally has influenced the recent research in environmental engineering but air-conditioning is still widespread and its use set to increase progressively. Architecturally the reliance on mechanical cooling has had the effect of thermally disconnecting the occupants from their climatic context creating sealed spaces where the building no longer responds to the local external climate. Amongst several lines of research in passive cooling in the past 20 years, Passive Downdraught Evaporative Cooling (PDEC) has been proven as a viable alternative to conventional mechanical cooling in buildings located in dry-hot climates. Following the theoretical and experimental work by Givoni, in Israel and by Cunningham & Thompson, in Arizona, a number of pioneering buildings adopting this innovative technique have emerged around the world. These first generation buildings demonstrate the technical applicability of PDEC as part of a climatically responsive approach to design and to the provision of comfort. However, many questions arise on the design implications of a PDEC building and specifically on the relationship between system performance, architectural integration and occupants’ perception.
Four case study buildings using PDEC were identified in the states of Arizona, Utah and California, for which a post occupancy study was undertaken by the author, as part of a dissemination project supported by the European Commission and completed in 2010. These buildings use various PDEC system typologies and approaches to building integration. This paper reports on the outcome of this study, which has shown that the ‘success’ of a PDEC system is often related to the ability of the designers to anticipate the implications for the users of their buildings (i.e. building integration) and to the robustness of the overall passive design strategy. The study also showed that the occupants’ perception of such buildings is influenced by their expectations (pre-conditioning) and by their ability to control their surrounding environment.