ATLANTA - A 10-step guideline for use in designing displacement ventilation systems is available from the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE). According to ASHRAE, while displacement ventilation has not been widely used in the United States, its potential for use is great, due to the existence of large core offices in many U.S. buildings that are isolated from the external climate and that need cooling.

System Performance Evaluation and Design Guidelines for Displacement Ventilation is the result of an ASHRAE research project by Qingyan Chen, Ph.D., professor of mechanical engineering, Ray Herrick Laboratories, Purdue University, West Lafayette, Ind., and Leon Glicksman, Ph.D., professor of building technology and mechanical engineering, Massachusetts Institute of Technology.

"Our results show that displacement ventilation systems can provide a thermally comfortable indoor environment at a high cooling load through careful design," Chen said.

Displacement ventilation is used mainly in Scandinavian countries. Many U.S. cities have higher temperatures in summer than those in Scandinavian cities, and U.S. offices may have more lighting and equipment that produces more heat. Therefore, the cooling load could be higher.

With displacement ventilation, warm contaminants rise to the ceiling, the contaminated air is extracted, and fresh, cool air is supplied at floor level.

"The indoor air quality is better if the contaminant sources are associated with the heat sources, such as computers, people, and equipment," Chen said. "This is because the thermal plumes from the heat sources will bring the contaminants to the upper part of the room where exhausts are located. The displacement ventilation system can also save energy but requires a separate heating system if it is applied to building perimeter zones."

The cost of the guideline is $59 ($47, ASHRAE members).

To order, contact ASHRAE Customer Service at 800-527-4723 (United States and Canada) or 404-636-8400 (worldwide), fax 404-321-5478, by mail at 1791 Tullie Circle NE, Atlanta, GA 30329, or visit the ASHRAE bookstore at

Publication date: 11/10/2003