How Many Roof Vents Should You Have

You ll need the square footage of your attic to calculate the number of roof vents that you should need.

How many roof vents should you have.

8 perform similar calculations for the roof and ridge vents. First determine your attic area by multiplying the length by the width. Then aim for about 1 sq. As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.

A 30 x 40 ft. Attic for example has an area of 1 200 sq. In of vent opening per 150 sq. Attic ventilation requirements how many attic vents your roof needs.

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. Choosing round soffit vents for this home means that 8 square feet of required ventilation be divided by 0 196 for about 40 round vents. Solid vinyl soffit material costs the same as the vented material. Enter square footage calculate or enter the square footage of the attic or area to be vented.

Industry standard for proper attic ventilation recommends for no vapor retarder type of attic insulation no paper plastic or aluminum layer between the attic floor and insulation layer 1 sq. If the home already has a fan roof vents or gable vents these should be blocked and sealed from the attic side of the home. Then you can begin choosing the style and type of roof vents you want for your home. Hot air exhaust vents located at the peak of the roof allow hot air to escape.

Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. It s important to remember that it s better to have too much intake ventilation than too little and many homes often undercalculate the amount of intake needed so worry less about having too much intake and err on the side of having more. Taking advantage of this natural process referred to as passive ventilation is the most common way to vent an attic. The building code lets you reduce that by half under some conditions but more roof ventilation is usually better.

For example if you have 1200 square feet of attic space you should need at least 4 air vents to ensure proper ventilation. With any attic ventilation system the attic can be 20 degrees hotter than outside. Feet of attic space divided 50 50.