How Far Apart Should Roof Vents Be

Proper installation number and location of roof ventilation is needed to maximize the performance of a roof.

How far apart should roof vents be.

Space the vents at the bottom and top of the attic equally according to house size. In this example the section of roof is 20 feet wide and 14. Vegetation must not be allowed to grow within 3 feet of an exhaust vent. In all areas exhaust vents should be at least 1 foot above roof surface.

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. Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. Fan calculation as a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space. Some people install the ridge vent the easy part and leave older gable end vents as intake this does not work very well.

The same concept holds true for roof trusses. 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. 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. This allows air to circulate over the insulation taking away any moisture evaporating upwards or trapped in the insulation fibres.

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. 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. 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. 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.

Exhaust vents must be protected against rain and equipped with back flow prevention features e g flap dampers. Proper roof vent location for air intake and outlet. Exhaust vents must not be allowed to be obscured or hidden by vegetation. 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.

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. 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.