Project at a Glance

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 this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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