A Dynamic Ceiling for Improved Comfort with Evaporative Cooling

Marc Zuluaga and Dianne Griffiths, Steven Winter Associates

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Abstract

In dry climates, evaporative cooling offers significant energy and peak demand reductions compared to compressive air conditioning. One of the main barriers to its greater implementation is a difficulty in maintaining occupant comfort on design days. For this reason, envelope upgrades that reduce peak cooling loads are especially beneficial when evaporative cooling is being considered since sufficient reductions can make it a more viable alternative.

Ceiling heat gains may be eliminated if a portion of the conditioned air normally exhausted through open windows during evaporative cooling is first directed through air permeable “dynamic” attic insulation before finally being expelled to a vented attic. The load reductions associated with integrating evaporative coolers with the buildings that they cool in this manner will be greatest during design conditions. In addition to reducing sensible load during these critical periods, controlled ceiling intake locations distributed in different rooms will aid in the circulation of conditioned air throughout a house that is typically supplied to only one central location by an evaporative cooler.

With co-funding from the California Energy Commission and DOE’s Building America Program, Steven Winter Associates has developed a furred ceiling design with a small number of controlled openings that allows conditioned air to be uniformly exhausted through attic insulation. Test chamber results demonstrate that a relatively small airflow rate is necessary to eliminate ceiling gains and that this airflow can be captured with a design that does not significantly depart from standard practice. A prototype dynamic ceiling house will be constructed in 2004.