Proper Attic Ventilation Requirements

The following are the requirements taken directly from the irc.

Proper attic ventilation requirements.

If you don t see any attic vents on the roof or in the eaves you need to add some. Of vent for every 300 sq. Rafter vents should be placed in your attic ceiling in between the rafters at the point where your attic ceiling meets your attic floor. You can also contact your local municipality to check on building code in your area.

Most building codes require a ratio of 1 150 ventilation space to attic floor space. Look at your eaves and roof. You can go as low as 1 300 of the attic floor area for attics which have a continuous vapor barrier below to a high of 1 5 in inches x the floor area in feet. The ventilation ratios go according to attic floor size not roof size.

Your roof vents may not look. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. That is a huge difference in allowance.

Proper ventilation necessitates that fresh air is able to find its way in the attic space while allowing stale air to get out. Once they are in place you can then place the batts or blankets or blow insulation right out to the very edge of the attic floor. The ventilation amount and opening size requirements can be found in section 806 roof ventilation of chapter 8 roof ceiling construction. This is accomplished through the placement of ventilation near the bottom of the attic space at the soffits or eaves intake and at the top peak s or ridge s of your attic space exhaust.

There should also be a 50 50 balance of attic venting and roof venting. Touch your ceiling on a warm sunny day. Measure the length and width of the attic floor space to be ventilated. A hot ceiling tells you that the attic is acting like a solar oven raising your cooling bills and.

Regarding attic ventilation nrca recommends designers provide at least 1 square foot of nfva for every 150 square feet of attic space 1 150 ventilation ratio measured at the attic floor level ceiling.