ASHRAE 62.2 “Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings” is the U.S. national minimum ventilation standard. Note that not all states require it or may apply it differently so check with your local building codes to see what they require.
The standard requires low-level, continuous ventilation in a home using a whole-building fan or other ventilation system. Intermittent whole-building ventilation can be used as an alternative. Note that the standard uses the term “whole-building ventilation fan”, not to be confused with the term “whole-house fan” which is a different product (see AirScape whole-house fans on hvacquick.com.
To calculate the required flow for continuous ventilation, count 1 cfm (cubic foot per minute) per 100 square feet of floor area of the house. Next, multiply the number of bedrooms plus one by 7.5 cfm (cubic feet per minute). Then add those results together. For example, a 2,000-square-foot house with three bedrooms would require 50 cfm (20 cfm for the building area plus 30 cfm for the 3+1 bedrooms).
Typically HRVs or ERVs are used to meet the standard, but bath fans are acceptable as well. There are additional sound and minimum cfm criteria that bath fans must meet in order to be allowable. Fantech and S&P inline fans are a good option due to their low sound levels and available 62.2 control options:
http://www.hvacquick.com/products/residential/Ventilation-Accessories/ASHRAE-62-2-Controls
An online version of the standard is available at the ASHRAE website (www.ashrae.org).
