 Building Science at UC Berkeley: Research
Edward Arens, Department of Architecture & Director, CEDR University of California Energy Institute There are several opportunities to save energy by cooling building interiors with wind-induced air motion. They result from increased heat transfer rates from either the building’s interior surfaces or from the building occupants themselves. With such air movement, building can be passively precooled during period when the outside air is cooler, such as at night. In addition, the occupants experience increased sensible and latent heat removal that offsets higher ambient air temperatures and radiant temperatures. Thus, wind-driven natural ventilation can be used during night or day or both, depending on the climate. In the past it has been impossible to predict the interior air motion resulting from forced convection through openings in the building envelope. The problem is not simple because interior air flow is a complex consequence of several scales of building geometry, site obstructions, and outdoor wind. It is not surprising that there have been virtually no design tools for this purpose. The absence of tools has, however, acted to suppress design thinking about this form of convection heat removal, and has led to the assumption that mechanical air conditioning is essential for removing heat from buildings during warm seasons. In order to address this problem, we have completed a series of wind tunnel experiments that have produced mathematical functions linking climatic wind records, a description of the building surroundings, the resulting wind pressure on building surfaces, and the interior air velocities resulting from those pressures. The functions appear to be robust at representing ventilation within complex building and site geometries and have matched full-scale data where available. The project is in its final experimental stages, developing a model of the effects of building surroundings on the wind pressures that drive the completed ventilation model.
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