How Much Roof Ventilation Do I Need

Jones must now take this required ventilation space and compare it against the total ventilation that he currently has for his attic space.

How much roof ventilation do i need. Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. 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. Building codes vary. 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.

That depends on a few different variables including the size of the roof the roofing material and what the building will be used for. 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. Static ventilation needs may be reduced if you have an uninterrupted ceiling vapor barrier installed with a rating of 0 1 perm or less. As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.

Of vent for every 300 sq. That said air resistance and interference such as vent grates reduces the area of true ventilation. Based on your 1100 sq. This yields a total area of 1 104 square feet.

Near ridge of the roof. 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. 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. Also your building codes may dictate how many and which kind of vents you need to use.

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. To calculate the ventilation required with such a vapor barrier divide the square footage of the attic by 300 instead of 150. Use these numbers to select proportion and place static ventilation products. If you have a hot roof or are getting one installed how much ventilation will it need.

Jones takes this measurement and divides it by 150 for a total of 7 36 square feet of ventilation space that is needed.