Attic Fan Ventilation Requirements

Vents are rated by their net free area or the amount of space for air to flow in or out.

Attic fan ventilation requirements.

Most building codes require a ratio of 1 150 ventilation space to attic floor space. Attic vent fans are commonly rated from 800 to 1 600 cfm making one fans suitable for attics of up to around 2 200 square feet. Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge. Attic ventilation fans could be effective if your home has.

Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. You can also contact your local municipality to check on building code in your area. Rafter vents ensure the soffit vents are clear and there is a channel for outside air to move into the attic at the soffits and out through the gable or ridge vent. Attic fans perform this ventilation by pushing hot air out into the environment while also pulling fresh cool air into the attic.

Calculate or enter the square footage of the attic or area to be vented. Of vent for every 300 sq. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Attic x 0 7 700 cfm minimum fan rating add an additional 20 cfm x 1 20 if you have a steep roof and 15 cfm x 1 15 for a dark roof.

Tips for assessing your needs. An attic floor that is thoroughly air sealed. Building codes vary. Ventilation openings having a least dimension larger than 1 4 inch 6 4 mm shall be provided with corrosion resistant wire cloth screening hardware cloth perforated vinyl or similar material with openings having a least dimension of 1 16 inch 1 6 mm minimum and 1 4 inch 6 4 mm maximum.

Complete coverage of the attic floor along with sealing air leaks will ensure you get the best performance from your insulation. Attic insulation that is less than r 19. You can calculate attic ventilation requirements by determining the square footage of your attic floor its width times its length and compare that to the total required net free area nfa. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

Hvac equipment in the attic that is well insulated and sealed.