A Really Cool Wall: Passive Cooling Building Skin for a School in Phoenix
Graduate Project, with Andrea Love [MIT] and Debashree Pal [Harvard]
The school is based in the hot and arid climate of Phoenix. The goal of the project is to greatly reduce energy usage with passive thermal, ventilation, and daylighting strategies. Thermal mass is used to shift loads and buoyancy effect drives the natural ventilation. Air is introduced to the space low and exhausted high as it is heated by occupants and equipment. Nighttime flushing helps cool the interior surfaces to reduce the radiant temperatures during the day.
During parts of the year with extreme heat, evaporative downdraft cooling towers are utilized to cool the incoming air. Outside air passes through a wetted pad that is fed by a small electric water pump. The evaporation causes a decrease in temperature, and the cooler and heavier air drops down the tower. The dropping air causes more outside air to be pulled in from the outside.
The cooling towers become defining elements on the facade. They are made of precast concrete panels with surface impressions for self shading. The depth of the impressions very by orientation and cut the amount of solar radiation falling on the surface by as much as 75%. The cooling towers also act as an exterior shading device to block direct sunlight and solar heat gain.