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Active vs. Passive Roof Ventilation

Passive and active are the two main types of attic ventilation. Each method has its pro and cons and the best option for your home will depend on your specific situation. 

Passive Attic Ventilation

Passive attic ventilation relies on natural forces, such as wind and temperature differences, to draw air through the attic. This can be achieved through the use of soffit vents, roof box vents, or ridge vents, which allow air to flow in and out of the attic. This type of ventilation is generally considered to be the most cost-effective and energy-efficient option, as it does not require any additional power or maintenance.

Examples of passive attic ventilation:

Soffit vents - an intake vent installed in the underside of the eaves or soffits of a building to allow fresh air to enter the attic or roof space. Soffit vents are well protected by the roof but also are susceptible to blockage.

Roof mounted box intake vents – box style vent that is designed to be mounted lower on the roof and provide intake airflow.  Since these vents are installed on your rooftop they are more exposed to the elements than soffit vents.

Static box vents – exhaust vent installed near the peak of the roof, these vents are simple to install and maintain. With its 360-degree open area, it provides ample space for efficient air exhaust. However, it's important to note that historically, these vents have been susceptible to potential leakage caused by wind-driven rain and snow.

Slant back vents – slant back vents are roof exhaust vents that feature a sloped design that helps to protect against wind-driven snow and rain.  This slant design also means there is an enclosed space within the vent where snow and other particulate can accumulate.

Ridge vents – exhaust vents designed with a narrow opening that spans the entire length of the roof ridge, seamlessly blending into the roofline. These vents are complex to install and also do not provide protection against blowing snow and rain

Tower vents – tower vents are exhaust vents that have their opening a few feet above your roofline, in theory this makes it harder for snow and other particulate to enter. These vents are taller than other vent types and are therefore more impacted by wind.

Gable vents – these vents typically provide exhaust airflow and are located near the peak of a gable end, the triangular-shaped wall section at the end of a building. These types of vents are easy to install and maintain but proper ventilation depends on wind direction and they are also prone to leakage.

Active Attic Ventilation

Active attic ventilation uses powered fans or mechanical devices to push air through the attic, which can be more efficient at eliminating heat and moisture with fewer vents. However, this method requires more energy and maintenance due to the presence of moving parts. Additionally, there is a risk that too much air may be removed from the attic, which can be replaced with treated air from the living space. It is essential to properly seal the attic and balance intake and exhaust vents to avoid this issue.

Examples of active attic ventilation:

Turbine Vents - Turbine vents, also known as whirlybird vents or rotary vents consist of a spinning turbine-like structure with vanes or fins that rotate when exposed to wind or air movement. This type of vent is wind powered, providing the benefits of active ventilation with no electricity cost.  The moving parts on this vent will require more maintenance than a passive vent and are also dependent on wind direction to work properly.

Power Vents – low profile circular-shaped vents that incorporate a fan and motor to exhaust air from your attic.  These vents will work effectively regardless of wind direction but the motors that power them are prone to breaking.  Maintenance will be required.

Solar powered vents – these vents function similarly to traditional power vents, however, instead of relying on electricity from the grid, they harness solar energy to drive the fan.  Solar vents are typically expensive up front but provide cost savings during the lifetime of your roof as they are powered by the sun.  Solar vents only operate during the day and only when the sun is shining, meaning your attic may be under ventilated at certain times.

Active vs. Passive Comparison

Passive attic ventilation is generally considered the optimal choice for most homes as it is natural, cost-effective, and energy-efficient. It requires minimal maintenance and produces less noise compared to active ventilation. A properly designed and installed passive ventilation system will effectively ventilate your attic without any additional input. However, in some instances, active ventilation may be necessary to address specific issues such as high humidity.

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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


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


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 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.

Lower Roof Intake Vent

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

Skylite Exhaust Vent

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

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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?
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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 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 vents have been tested to allow for airflow even under heavy snowfall conditions. See the link below for video proof.

Will SNOWVENTCO 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.

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