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Understanding Passive Roof Vents

Passive roof vents are the most prevalent type of ventilation system found in homes, relying on natural airflow to ventilate the attic space. Box vents, ridge vents, and gable vents are common examples of passive vents. Passive airflow occurs due to the chimney effect, where air buoyancy results from indoor-to-outdoor air density differences caused by temperature and moisture disparities. The efficiency of passive ventilation depends on various factors, including attic temperature, ambient temperature, air moisture content, wind velocity, roof pitch, and roof height.

Active Roof Vents for Enhanced Ventilation

Active roof vents use a motor, fan blade, or turbine to exhaust air from the attic. The volume of air these outlets can transport every minute is expressed in cubic feet (CFM). Wind turbines, wire-powered vents, and solar-powered vents are popular active vent types. Active roof vents provide more consistent airflow than passive vents, exchanging attic air with fresh outdoor air much faster.

roof with limited ventilation

Challenges with Passive Ventilation

  1. Limited roof space for vents: Unique roof shapes like hip roofs may not have enough space for proper ventilation due to their large attic spaces, short ridge lines, and limited room for box vents.
  2. Complex roof structures: Roofs with intricate shapes, cavities, and corners are more challenging to ventilate, accumulating heat and moisture despite meeting the minimum passive vent requirements.
  3. Low-pitched roofs: Roofs with slopes lower than 3:12 are at a higher risk of poor airflow, as the chimney effect relies on attic height for adequate passive airflow. Building codes often recommend doubling the number of vents for low-slope roofs.

Enhancing Attic Airflow with Solar-Powered Vents

Canada Go Green solar-powered vents offer active ventilation during the day and passive ventilation at night. These vents work the hardest when the sun shines, moving up to 400 CFM each and increasing attic airflow. The CFM level will drop slightly on cloudy or overcast days when there is less need for high levels of air movement. At night, solar-powered vents continue to function as traditional passive vents.
Invest in energy-efficient and eco-friendly solar-powered attic ventilation systems to optimize your home’s roof ventilation. Contact us to learn more about solar powered vents and improve your home’s energy efficiency.

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