For example 1 500 square feet of attic space requires 10 square feet of vent space.
How far apart for roof vents.
Thus if your attic is 450 square feet you need roof vents equaling 3 square feet.
Exhaust vents must be protected against rain and equipped with back flow prevention features e g flap dampers.
Take the solution and divide it by 150.
As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.
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.
If you have 3 000 square feet of attic space this equates to 20 square feet of ventilation needed.
Vegetation must not be allowed to grow within 3 feet of an exhaust vent.
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.
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.
Ventsure 4 foot strip heat moisture ridge vent.
The final number will be the total vent space needed for your attic.
In all areas exhaust vents should be at least 1 foot above roof surface.
Measure the length and width of the attic and multiply the two together.
Ft you divide that by 150 to get 10 sq.
This ratio is required for modern insulated homes.
Of vent space for every 150 sq.
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.
What is the standard spacing of a roof rafter.
Choose one of the following products to meet the recommended exhaust nfva of 528 square inches.
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.
Exhaust vents must not be allowed to be obscured or hidden by vegetation.
Ventsure 4 foot strip heat moisture ridge vent with weather protector moisture barrier.
Otherwise the exiting air at the ridge will usually pull its makeup air from the closer gable end vents and not from the soffit or eaves vents.
27 lineal feet required.
This allows air to circulate over the insulation taking away any moisture evaporating upwards or trapped in the insulation fibres.
So if your attic is 1 500 sq.
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.
