How Far Apart Should Roof Vents Be

So the space between rafters can be greater without reducing the maximum span.

How far apart should roof vents be.

Some people install the ridge vent the easy part and leave older gable end vents as intake this does not work very well. 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. This allows air to circulate over the insulation taking away any moisture evaporating upwards or trapped in the insulation fibres. The general rule of thumb on the amount of total attic vent space needed is to have at least one square foot of vent space for every 150 square feet of attic area.

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. Common spacing for trusses on this type of building is often between 2 and 4 feet but trusses built with advanced designs may allow spacing as great as 8 or 12 feet. In all areas exhaust vents should be at least 1 foot above roof surface. Proper installation number and location of roof ventilation is needed to maximize the performance of a roof.

Proper roof vent location for air intake and outlet. 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. Exhaust vents must be protected against rain and equipped with back flow prevention features e g flap dampers. For the previous example you would need 20 soffit vents.

Fan calculation as a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space. Measure the section of the roof from the fascia to the peak and divide this by two which is the two foot spacing of the wood nailers. Space the vents at the bottom and top of the attic equally according to house size. You need to have an equal number of vents located at the bottom of the attic or under the roof easement as you have at the top of the attic near a gable or ridge.

This video has examples of both static and ridg. The same concept holds true for roof trusses. Ideally half the vents should be located in the soffit at the bottom of the roof and half in gable or ridge vents near the top to allow for natural circulation of air through the attic. Thus if your attic is 450 square feet you need roof vents equaling 3 square feet.

Simply pulling in the needed makeup air from typical gable end wall vents will not move air under the lower and center areas of roof sheathing thus inadvertently. Vegetation must not be allowed to grow within 3 feet of an exhaust vent.