How Far Apart Should 3 Roof Vents Be Placed

As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.

How far apart should 3 roof vents be placed. Fairly simple stuff fresh air in old stale air out. Ft divided by 150 equals 10 sq. For the previous example you would need 20 soffit vents. The federal housing authority fha requirement for attic venting is 1 square foot of venting for every 300 square feet of attic space.

Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. One square foot equals 144 square inches so the standard 16 inch by 8 inch soffit vent is 0 89 square feet. 2 snow guards per valley every 10 feet of roof. It should be noted that these vents which expel warm moist air from the bathroom and food prep areas of the home need their own ducts and vent hoods which direct air to the home s exterior.

When finished there should be a row of furring strips stretching from one end to another with the top edge aligned at the peak. Attic systems may use registers placed in the ceiling instead. 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. These vents and ducts should never share space with the roof vent and air should never be vented directly into the attic.

Calculate the total vent area needed. Different forms of high and low level ventilation are used as well apart from the soffit vents and ridge vents pictured. 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 there are gaps around the roof penetration or valley points cut extra sections of furring to fit.

Builders refer to this as the 1 in 300 rule and it requires that the total venting space should be at least shared equally between the soffit and roof vents. Length x width of attic in feet 150 total sq. A 50 x 30 attic would have a total area of 1 500 sq. 3 12 up to 4 12 pitch.

The supply vents which push air through the duct work must be placed properly. Pick out your soffit vent size and determine the square footage of the vent. Divide this by 144 to calculate how many square feet each vent is. Many have duct work in crawlspaces so the registers are placed in the floor.

In this case their height will be determined by your system. Place it two feet apart from the first row. Up to 45 psf ground snow load. Roof ventilation this picture represents what is considered to be the best way to ventilate a roof space.

Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find the total square feet of vent space needed. Of total vent space needed.