ASHRAE Standard 62.2-2007, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings, is the national ventilation standard of design for all homes 62.2 allows exhaust, supply, or balanced ventilation, meaning that a simple exhaust fan or supply fan can be used, or these flows can be balanced with both a supply fan and an exhaust fan, with or without heat recovery. It is up to the architect or builder to decide if filtration, tempering, or dehumidification is required, based on where the house or building is built.
The ASHRAE 62.2 fan sizing is based on total square footage of the home and number of bedrooms. The formula is; (total square footage of the home/100) + ((number of bedrooms+1) X 7.5 cfm). For example; a 2500 square foot house with 3 bedrooms needs ((3+1) x 7.5) + (2500/100) = 30 + 25 = 55 cfm.