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How many roof vents do I need?

Requirements depend on several factors

When it comes to attic ventilation, the number of vents you need can vary depending on the size of your attic and the type of ventilation system you have. The most common type of attic ventilation is passive, which relies on natural air flow to ventilate the attic space. To determine the optimal number of vents for your roof, you'll need to take a few factors into consideration.

Measure the size of your attic

First, you'll want to consider the size of your attic. The larger the attic, the more vents you'll need to ensure proper ventilation. As a general rule, you should have at least one square foot (144 square inches) of ventilation for every 300 square feet of attic space. So, for example, if your attic is 1,500 square feet, you would need at least 5 square feet (about 750 square inches) of ventilation.

Check your vent specifications

Another factor to consider is the type of vents you're using. There are several types of vents, including soffit vents, box vents, and ridge vents. Each type of vent serves a specific purpose and will have a different measure of NFA (Net Free Area, a measure of the flow of each vent).   You will need to balance exhaust and intake evenly as well as ensuring the NFA of the vent you are using will provide enough airflow through your attic.  Try our easy-to-use roof vent calculator to see the recommended amount of vents for your roof.

Consider your climate

Finally, you'll want to consider the climate in your area. In hotter climates where humidity can be a problem, slightly more vents may be needed to allow hot air to escape, while in colder climates where heat loss is the bigger problem, slightly fewer vents may be needed to prevent heat loss.

How many vents do you need?

The optimal number of roof vents depends on the size of your attic, the type of vents you're using, and the climate in your area.  Typically more vents are better than less and the general 1/300 square feet recommendation does not need to be followed strictly.  It's always a good idea to consult with a roofing professional to ensure that you have the right number and type of vents for your specific situation.

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Chislett Roofing has been in business for over 40 years and we shingle over 4,000 homes each year in Ontario. In the winter, constantly blowing snow through roof vents can be a real problem in our area. We have used SNOWVENTCO roof vents for years and their snowproof stainless steel filter is a great solution. These vents are a little more expensive, but leaking vents silently destroy attic insulation. Today over 90% of our installs use only SNOWVENTCO.

Bill Chislett

Chislett Roofing

Newmarket, Ontario

About time someone made a vent that does what it's meant to all year round!!! Good vent - will use on all my own roofing jobs.

Krzysztof Wolf

Roofer

Toronto, Ontario

The roof vents in today's market are very low quality, have a short life span and a high tendency to fail. This leaves homeowners with multiple problems including bugs/wasps, mould, overheated roofs and, most of all, water damage caused from leaking and major snow intake. When I first saw the new SNOWVENTCO Roofers' Vent I immediately liked its sleek look as well as its craftsmanship and durability. I would recommend this vent to anyone without hesitation. It's by far the most state of the art roof vent available today.

Dave Flynn

Roofer

Brighton, Ontario

I have not had a good product available to stop the snow from being blown into an attic during a windy snow storm, UNTIL NOW! The SNOWVENTCO Roof Vent will be the ONLY vent I recommend for use on any roof in any location that ever gets snow! A journeyman roofer from Germany taught me the roofing trade, but was always looking for a good vent that would keep snow out. Now we have a good vent, one that really works, available for our customers.

Francis E. Harris

Roofing Company Owner

Calgary, Alberta

SNOWVENTCO Snow Vents

snowventco upper roof exhaust vent in black polypropylene

Upper Roof Exhaust Vent

Install near roof peak to allow warm air to escape. Blocks 99% of snow, diverts rain.

a group of three snowventco lower roof intake vents in brown, grey and black

Lower Roof Intake Vent

Suitable for use in place of soffit vents. Blocks 99% of snow, effectively diverts rain.

translucent version of snowventco storm vent to allow light into a shed while keeping rain and snow out

Skylite Exhaust Vent

Perfect for sheds and garages to allow light in while keeping moisture out.

30 day
MONEY BACK
GUARANTEE
30 YEAR
WARRANTY
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in CANADA & USA*

Frequently Asked Questions

Why do I need roof vents?
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Roof vents are necessary in order to improve the ventilation in your attic. Adequate ventilation helps to remove excess heat and moisture from your attic, which can prolong the life of your roof and prevent damage to your attic and the rest of your home. Additionally, proper ventilation can help to prevent the growth of mold and mildew, which can be a health hazard.

What is the best roof ventilation system?
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There is no one "best" roof ventilation system as the appropriate system will depend on the specific needs of your home and roof. Roof vents are generally divided into active or passive systems with each system having its pros and cons.

How many roof vents do I need?
arrow down to open frequently asked question

The number of roof vents you need will depend on the size and layout of your attic. A general rule of thumb is to have 1 square foot (144 square inches) of vent area for every 150 square feet of attic space. For example, if your attic is 900 square feet, you would need 864 square inches (6 square feet X 144) of vent area. Additionally, it's important to make sure that your vents are properly placed and balanced, with an equal amount of intake and exhaust vents. This will ensure that air is flowing effectively through your attic and not creating pressure that could cause leaks or damage to the roof. Try our roof vent calculator to find the right amount of vents for your roof.

How Do I Install SNOWVENTCO Storm Vents?
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Installing roof vents can be a complex task that requires a certain level of skill and experience. It is recommended that you hire a professional roofing contractor to install your vents, as they will have the knowledge and tools necessary to do the job safely and correctly. However, if you're determined to install them yourself, take a look at our installation video for a step by step demonstration.

Can raccoons, squirrels, or other rodents chew through the vent and gain entrance into my attic?
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No, determined vermin will have a difficult time chewing through the heavy duty plastic outer shell which is much thicker than typical roof vents. If they are able to chew through the plastic they will not be able to get through the stainless steel filter. This will restrict attic access through the vent openings.

Can roof vents breathe under snow?
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Roof vents can breathe under snow, but it depends on the amount of snow and the type of vent. SNOWVENTCO Storm Vents have been tested to allow for airflow even under heavy snowfall conditions. See the link below for video proof.

Will SNOWVENTCO Storm Vents perform well under high wind conditions?
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Yes, the low profile and aerodynamic design of SNOWVENTCO vents combined with heavy duty polymer outer shell mean the SNOWVENTCO vents are very resistant to high winds. Our vents have undergone testing showing that they prevent over 99% of rain, snow, and other particle penetration of attic in CAT 3 hurricane wind conditions. They are also durable enough to stay intact when faced with 120 mph winds.

Still have questions?

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Keep Your Attic Dry

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30 day
MONEY BACK
GUARANTEE
30 YEAR
WARRANTY
FREE
SHIPPING

in CANADA &
CONTINENTAL USA