Take the solution and divide it by 150.
How far apart for roof vents.
The final number will be the total vent space needed for your attic.
Exhaust vents must be protected against rain and equipped with back flow prevention features e g flap dampers.
For example 1 500 square feet of attic space requires 10 square feet of vent space.
Vegetation must not be allowed to grow within 3 feet of an exhaust vent.
Ft you divide that by 150 to get 10 sq.
If you have 3 000 square feet of attic space this equates to 20 square feet of ventilation needed.
27 lineal feet required.
So if your attic is 1 500 sq.
Of vent space for every 150 sq.
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.
Optimum roof ventilation design.
These spacing intervals are measured on center meaning that the measurement is taken from the center of one rafter s horizontal surface to the center of the next rafter.
But they do tend to space rafters in one of several industry standard increments typically either 12 16 or 24 inches apart.
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.
As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.
Measure the length and width of the attic and multiply the two together.
The rule of thumb on the amount of vent space needed is approximately 1 sq.
What is the standard spacing of a roof rafter.
This ratio is required for modern insulated homes.
Ventsure 4 foot strip heat moisture ridge vent.
Divide the square footage by 150 to calculate the area of ventilation needed since you need 1 square foot of vent space for each 150 square feet of attic space.
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.
Provides continuous ridge venting continuous soffit venting and then close off those old gable end vents to force the intake air to come where you want it to flow.
In all areas exhaust vents should be at least 1 foot above roof surface.
Ventsure 4 foot strip heat moisture ridge vent with weather protector moisture barrier.
Thus if your attic is 450 square feet you need roof vents equaling 3 square feet.
This allows air to circulate over the insulation taking away any moisture evaporating upwards or trapped in the insulation fibres.
In my opinion one of the best places to fit roof tile vents is normally the bottom third of a roof just above insulation level.
