Page 63 - Zero Net Energy Case Study Buildings-Volume 3

LA ESCUELITA EDUCATION CENTER
CASE STUDY NO. 13
Natural Ventilation
A form of natural ventilation is used for fresh air and cooling in place of standard air conditioning for the Great Room, namely the “Cool Tower” feature described below. The classrooms utilize openable windows controlled by the occupants, but the primary system for providing ventilation air is displacement ventilation1.
Heating, Ventilating and Cooling Systems
The “ZNE Group” utilizes two innovative heating and cooling systems that avoid the use of conventional compressors in mechanical air conditioning systems, as required by District policy, and make use of the natural properties of air to minimize the use of fans. The first system, applicable to larger spaces, was named the “Cool Tower” by the design team and is used to provide cooling air to the Great Room. (The “Cool Tower” is not to be confused with conventional cooling towers in air-conditioned buildings.) Without the use of any fans whatsoever, the Cool Tower initiates the designed movement of air through the space to ensure comfortable thermal conditions at all times of the year and for varying number of occupants in the room.
Two Cool Towers located on alternate sides of the west end of the Great Room act like “air scoops” for the consistent prevailing breeze off San Francisco Bay. (See cutaway diagram be- low.) For added cooling, fine mist sprays inside the Cool Towers create an evaporative cooling effect and lower the temperature of the incoming air to the level required. Within the space, displacement ventilation causes the air to rise due to the natural buoyancy of the air entering the space and the heat from the occupants in the room. The air is ultimately exhausted through the pressure relief louvers in the upper walls at the north clerestory windows. When the temperature in the space rises past the cooling setpoint, additional cooling effect is created by higher air ve- locity through the space by several large-diameter (18’) room fans.
The design works well in this California coastal marine climate, which is somewhat dry (allowing evaporative cooling to be effective) and moderate in temperature. Extensive calculations were
1 Displacement Ventilation is a room air distribution strategy where conditioned outdoor air is supplied at a low velocity from an air supply located near floor level and extracted above the occupied zone, usually at high ceiling height.
(Below) Cutaway diagram
of Cool Tower in the Great Room. Intake air is cooled by a water mist spray (above) and drawn into the room by natural air buoyancy and rising heat of the occupants. (Courtesy of SVA Architects)
Zero Net Energy Case Study Buildings, Volume 3
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