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.