How Much Roof Ventilation Do I Need

Use these numbers to select proportion and place static ventilation products.

How much roof ventilation do i need.

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. As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space. Also your building codes may dictate how many and which kind of vents you need to use. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.

Static ventilation needs may be reduced if you have an uninterrupted ceiling vapor barrier installed with a rating of 0 1 perm or less. That depends on a few different variables including the size of the roof the roofing material and what the building will be used for. 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. If there is no vapor barrier double it to one square foot of nfa for every 150 square feet of attic floor space half for intake half for exhaust.

This yields a total area of 1 104 square feet. Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. Near ridge of the roof. They should be divided equally between inlet and outlet vents and they can be used in any combination that will work with your roof s design.

Building codes vary. 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. This shortcut conveniently calculates the 2015 international residential building code minimum irc section r806 roof ventilation 1 which states in part 1 square foot of net free area for every 150 square feet of attic floor space with the attic defined as length x width floor of the attic. And this guideline you ll need a minimum of.

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. Jones must now take this required ventilation space and compare it against the total ventilation that he currently has for his attic space. To calculate the ventilation required with such a vapor barrier divide the square footage of the attic by 300 instead of 150. Based on your 1100 sq.

If your attic floor has a vapor barrier you will need one square foot of nfa per every 300 square feet of attic floor area half of that will be intake half for exhaust.