Attic Cross Ventilation

You can also contact your local municipality to check on building code in your area.

Attic cross ventilation.

That said air resistance and interference such as vent grates reduces the area of true ventilation. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Intake vents located at the lowest part of the roof under the eaves allow cool.

Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. Proper insulation and air sealing also keeps attics cold in winter by blocking the entry of heat and moist air from below. The soffit vents are now installed but you still need to make sure there s no insulation blocking the new vents. Most building codes require a ratio of 1 150 ventilation space to attic floor space.

Generally speaking you need a ratio of 1 300 where for every 300 square feet of ceiling space you need 1 square foot of attic ventilation. In the summer natural air flow in a well vented attic moves super heated air out of the attic protecting roof shingles and removing moisture. In other words the entire vent opening doesn t count as vented space.