Research Projects

Project at a Glance

Project Status: complete

Title: Study of ventilation practices and household characteristics in new California homes.

Principal Investigator / Author(s): Piazza, Thomas

Contractor: UC Berkeley

Contract Number: 03-326

Research Program Area: Health & Exposure

Topic Areas: Indoor Air Quality


A survey was conducted to determine occupant use of windows and mechanical ventilation devices; barriers that inhibit their use; occupant perception of and satisfaction with indoor air quality (IAQ); and the relationships among these factors.
A questionnaire was mailed to a stratified random sample of 4,972 single-family detached homes built in 2003, and 1,448 responses were received. A convenience sample of 230 houses known to have mechanical ventilation systems resulted in another 67 completed interviews.


* Many houses are under-ventilated: depending on the season, only 10.50 percent of houses meet the standard recommendation of 0.35 air changes per hour.
* Local exhaust fans are underutilized. For instance, about 30 percent of households rarely or never use their bathroom fan.
* More than 95 percent of households report that indoor air quality is "very" or "somewhat" acceptable," although about one-third of households also report dustiness, dry air, or stagnant or humid air.
* Except in households where people cook several hours per week, there is no evidence that households with significant indoor pollutant sources get more ventilation.
* Except in households containing asthmatics, there is no evidence that health issues motivate ventilation behavior.
* Security and energy saving are the two main reasons people close windows or keep them closed.

Keywords: Indoor air quality, IAQ, mechanical ventilation systems, ventilation standards,
indoor pollutants, asthma, windows, exhaust fans, natural ventilation, thermal comfort


For questions regarding research reports, contact: Heather Choi at (916) 322-3893

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