Frequent Questions

How much ventilation do I need?

 The American Society of Heating, Refrigeration and Air-Conditioning Engineering (ASHRAE recommends (in its Standard 62-1999, "Ventilation for Acceptable Indoor Air Quality") that homes receive .35 air changes per hour, but not less than 15 cubic feet per minute (cfm) per person. A common rule of thumb is the 15 cfm multiplied by number of bedrooms in the house plus one. For example, a 3 bedroom house would require at least 60 cfm of outdoor air. [(3 bedrooms + 1) x 15 cfm = 60 cfm]. Kitchens should have an intermittent exhaust capacity of 100 cfm; bathrooms an intermittent capacity of 50 cfm. (ASHRAE also notes that "dwellings with tight enclosures may require supplemental ventilation supply for fuel-burning appliances, including fireplaces and mechanically exhausted appliances. See information on combustion appliances.)

For a basic overview of ventilation, including different types ventilation systems, try the following resources:

For a detailed analysis of ventilation system options for new homes, see the Lawrence Berkeley National Laboratory report Recommended Ventilation Strategies for Energy-Efficient Production Homes.  Copies of ASHRAE Standard 62 are available from ASHRAE.

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