Attic Vent Insulation Requirements

The majority of the requirements related to attic ventilation have not changed much from the previous editions.

Attic vent insulation requirements.

Attic ceiling to stop airborne moisture from reaching a cold surface and condensing inside the building envelope in this design insulation effectively separates the interior and exterior spaces while slowing down moisture flow so the dewpoint is not achieved within. Enter square footage calculate or enter the square footage of the attic or area to be vented. Whole house fans powered attic fans. For the same reason insulation shouldn t touch the roof s underside.

The following are the requirements taken directly from the irc. The recommended ventilation ratio to provide for vented attic assemblies when an air barrier is present is the 1 300 ratio as specified by most building codes. Fans and vents may be installed on the roof system that will draw the air out of the. Intake vents located at the lowest part of the roof under the eaves allow cool.

Code requirements the international building code. In addition insulation baffles must be installed at the point where the attic floor meets the roofline to prevent the attic insulation from migrating into the cavities and restricting the airflow from the soffit vents. 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. Roof insulation thermal resistance at roof perimeter should be equal or greater to thermal resistance of exterior wall.

The roofing industry also has practical guide lines for attic ventilation. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. Proper attic ventilation can be an impor tant performance consideration when design ing and installing steep slope roof systems.

Sure installing roof vents for older homes can reduce your hot air during the summer but there are probably more low risk cost effective ways to increase your home s energy. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Good roof ventilation can do this but shingle color sun exposure and insulation are exponentially more important to overall energy efficiency than ventilation. 1 300 ventilation ratio recommended.

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. Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator.