27 lineal feet required.
Number of vents for roof.
After that find out the vent s nfa as rated by the manufacturer.
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.
If your attic floor has an area of 1 500 square feet for example you need 10 square feet of ventilation space unless your house has a vapor retarding liner in which case you need 5 square feet.
The next step is to select a suitable exhaust vent and intake vent that fits the roof design for best performance and best aesthetics.
For example if your roof structure has a ventilated area of 150 m 2 and you wish to use the lomanco bib12 unit you would need three units for an efficient and balanced ventilation system.
It s time to install.
Advantages of proper roofing ventilation.
Divide the vent s nfa into 1 100 to yield the number of vents needed either in linear feet or units pieces.
Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation for every 300 square feet of attic floor space evenly split between intake and exhaust.
Ventsure 4 foot strip heat moisture ridge vent.
The rule of thumb used to determine the number of roof vents to install is one for every 300 square feet of attic area if your attic has a vapour barrier and one for every 150 square feet of attic area if the attic does not have a vapour barrier.
Thus if your attic is 450 square feet you need roof vents equaling 3 square feet.
As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.
Choose one of the following products to meet the recommended exhaust nfva of 528 square inches.
Use the factor 1 square foot 144 square inches to convert.
The table below is a guide that can be applied to most common roof types and pitches.
The federal housing administration recommends 1 square foot of attic ventilation for every 150 square feet of attic space.
Although there are many different types of roof vents to choose from ensuring you have the right number of both intake and exhaust vents is a central part of roof design.
Use the calculator below to find out how many exhaust and intake vents you will need on your house.
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.
Building codes typically echo the administration s guidelines.
Ventsure 4 foot strip heat moisture ridge vent with weather protector moisture barrier.
