Attic Fan Ventilation Requirements

An attic floor that is thoroughly air sealed.

Attic fan ventilation requirements.

Most building codes require a ratio of 1 150 ventilation space to attic floor space. 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. 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. Building codes vary.

Attic fans perform this ventilation by pushing hot air out into the environment while also pulling fresh cool air into the attic. 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. Attic ventilation fans could be effective if your home has. 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.

You can also contact your local municipality to check on building code in your area. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. Vents are rated by their net free area or the amount of space for air to flow in or out. 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. Calculate or enter the square footage of the attic or area to be vented. Tips for assessing your needs. 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.

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. The result is a cooler attic space with plenty of air exchange. 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. Bountiful eave soffit ventilation space.

Enter your square footage.