ARB Research Seminar

This page updated March 23, 2015

How Air Movement Makes Comfort Energy-Efficient

Photo of Edward Arens

Edward Arens

Photo of Hui Zhang

Hui Zhang

Edward Arens, Ph.D., and Hui Zhang, Ph.D., Center for Environmental Design Research, University of California, Berkeley

March 24, 2015
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


Air movement can cool a person indoors in a similar manner as lowering the temperature, but needs only a tiny fraction of the energy. New fans of 1-8 watts producing 0.6 to 1 m/s (1.5 to 2 mph) air movement near each of a building's occupants can offset a 6F (3K) increase in indoor air temperature, while actually improving the occupant's comfort and perceived air quality. Increasing the indoor temperature reduces a building's total HVAC (heating, ventilating, and air conditioning) energy about 5% per degree F, or 10% per degree C, and even more in climate zones where the indoor temperature allows natural ventilation or evaporative cooling systems to be used instead of compressor-based cooling. Across US climates, air movement permits year-round HVAC energy reductions averaging 1000 watts per occupant. The energy reductions possible from improved fan use exceeds that of many other current technological improvement to buildings.

The opportunities for new design approaches and new fan products are considerable. Room fans have many applications in both new and retrofit designs since they do not involve changing HVAC systems, can be easily turned on and off (as with occupancy sensors or wireless controls), and can provide an instantaneous cooling effect for the occupant. They strengthen the effectiveness of other energy-efficient measures that are inherently slow-acting or unpredictable, such as radiant ceilings/floors, and buildings designed to rely on natural ventilation. The technologies involved are especially applicable in California climates. However, it is important to be aware of possible unintended consequences of built environment energy management and possible impacts on indoor air quality.

The presentation addresses a wide range of topics ranging from fundamental human subject lab studies to new product designs, and to the removal of barriers to air movement in comfort and energy performance standards. This valuable project should not be regarded as the final word on the nexus of built environment energy reduction and potential indoor air and comfort impacts. Additional research in this area would be useful.

Speaker Biographies

Edward Arens, Ph.D., is Professor of the Graduate School at UC Berkeley. Dr. Arens is Director of the Center for Environmental Design Research, the University of California, Berkeley's research unit for building science and resource efficient urban design. Professor Arens is also Director of the Center for the Built Environment, an industry/university cooperative research center focusing on commercial/institutional buildings. Professor Arens received his Ph.D. in Architectural Science in 1972 from the University of Edinburgh, UK, and also holds a BA in architectural history and masters degrees in Forestry and Urban Studies from Yale University. Prof. Arens started UC's Building Science Laboratory in 1980 after heading the Architectural Research Section at the National Bureau of Standards. Dr. Arens has been principal investigator for a large number of State, Federal, and industry grants addressing building energy performance, indoor environmental quality criteria, field monitoring procedures, and architectural aerodynamics. Projects include developing wireless sensor systems for building control and electricity demand responsiveness, developing and testing new personal environmental control systems, human comfort testing and modeling, web-based surveying of occupant satisfaction in buildings, determining energy efficiency potential of thermally diversified environments, metrics for rating comfort and energy use in building perimeter zones, effects of humidity on comfort and health, and natural ventilative cooling. He is active in technical and standards committees of ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers), and co-founded SBSE (Society of Building Science Educators). Professor Arens has advised over 90 graduate students in the research track, and 18 Ph.D. students.

Hui Zhang, PhD, is a research specialist at the Center for the Built Environment at UC Berkeley. Her work focuses on human thermal comfort in complex environments and comfort modeling. She has been actively involved in ASHRAE Standard activities, and currently is a chair of the research subcommittee for ASHRAE Technical Committee 2.1 on Physiology and Human Environment. She holds a PhD in building science from the Department of Architecture at UC Berkeley. She received the ASHRAE Ralph Nevins Physiology and Human Environment Award for her Ph.D. dissertation study, "Local Thermal Comfort in Asymmetrical and Transient Environments." She received her M.S. in Architecture in 1986, and her B.A. in Engineering in 1983 from Tsinghua University, Beijing,China. Before she came to the U.S. in 1989, she taught in the Architecture Department of Tsinghua University as an assistant professor for three years. Previous research interests include energy conservation analysis in buildings, passive solar house design, and human thermal comfort.

For a complete listing of the ARB Research Seminars and the related documentation
for the seminars please view the Main Seminars web page