The 10 square feet X 144 square inches per square foot = 1,440 square inches required. If you are trying to determine the area in square inches, you can convert it by multiplying 144. To properly calculate the required roof ventilation, Section R806.2 specifies that the minimum net free ventilation area shall be 1/150 of the area being vented.įor example, an attic being 1,500 square feet in area requires 10 square feet of ventilation. Ventilation openings allow air to flow through the attic to remove any moisture and possibly minimize condensation problems within the attic and enclosed rafter spaces. To prevent this, the space within the attic must be vented to not allow the water to collect on the building components. Overtime this can cause the roof members to rot and decay.
Why is Roof Ventilation Required?Ĭommon activities around the house such as cooking, bathing, laundering, and even human breathing and perspiration can produce a large amount of water vapor that can make its way through the building envelope and into the attic.ĭue to the temperature difference between the attic and the conditioned space, the water vapors can reach a dew point where condensation can be present on the wood members in the attic.
RAFTER VENT HOW TO
Now before we talked about how to calculate roof ventilation, let us briefly go over why roof ventilation is required. We will discuss how these openings are required to be protected a little later in the post. These ventilation openings must also be protected from rain, snow, birds, rodents, and similar creatures while still providing enough opening to properly vent. Both enclosed conditioned will require ventilation. If an attic space is divided into separate spaces, each space is required to be vented, just like each enclosed rafter space is required to be vented.Īttic spaces are formed when ceiling joists are provided and enclosed rafter spaces are typical when a vaulted ceiling is provided.
RAFTER VENT CODE
Section R806.1 of the International Residential Code states the following:Įnclosed 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.īased on this code section there are two scenarios that will require attic ventilation: Enclosed Attics and Enclosed Rafter Spaces.īoth scenarios will require cross ventilation to be provided. Section R806 of the 2018 International Residential Code (IRC) outlines when roof ventilation is required and how to calculate it. When it comes to understanding what the roof ventilation requirements are for residential structures, we must look to the International Residential Code (IRC).
0 kommentar(er)
