Proper ventilation is a critical design and build decision for any new home roofing project. Ventilation contributes greatly to a building's performance in terms of energy use, longevity, and overall effectiveness.
Metal roof ventilation
When warm moist air comes in contact with a colder surface, condensation can occur. Nearly everyone has experienced a cold beverage in an aluminum can becoming wet with condensation on a warm day.
This same phenomenon can occur inside of your home. If you have an open air space, such as an attic or a large space between the roof panels and roof deck underneath, there is an opportunity for condensation to occur.
There are two ways to combat condensation inside of your home: insulation or ventilation. We won’t go into detail about insulation in this post, but think about your cold beverage in a foam cup for a moment, it almost never condensates because it’s protected with insulation.
Ventilation works by removing the warm moist air from the space before it has an opportunity to condense. For your home, you must give any warm moist air that enters the attic space an avenue of escape before it comes in contact with the underside of the roof assembly and condenses. Moisture in a roof space leads to a host of unwanted problems for any homeowner such as mold, mildew, and condensation which can soak insulation and possibly even ceilings and walls.
Other benefits to homeowners of proper metal roof ventilation include regulating temperatures in the home more easily and preserving air quality, all of which lead to a healthier environment for the occupants. Furthermore, ventilation will typically result in an energy performance improvement for your home.
How does ventilation work?
As we learned at a young age, heat rises. In buildings, warm air trapped inside of an open space will attempt to rise to the highest point of the structure, which is typically the ridge. For this reason, vents are placed near the top the roof to allow the warm air to escape naturally as it rises.
When warm air exits through the vents at the top of the structure, cooler air is drawn in from vents lower in the building – typically at the eave or around the soffit.
The video below demonstrates the movement of cool air being drawn from below, and warm air exiting from above.
Because the amount of air that exits at the ridge must be simultaneously drawn in from the eave or soffit, a critical factor in any successful metal roof ventilation project is having the same amount of airflow intake as airflow escape. Vent materials are usually specified in terms of net free ventilation area which is usually described as a total square inch area.
The amount of ventilation needed for your home or project will depend on the size of the building, we recommend consulting with an HVAC professional for your project.
There are two main types of venting for metal roofs: ridge vents and gable vents.
Ridge Vents
Low profile ridge vents are nearly unrecognizable from non-vented systems and often used with architectural style roofs because they are designed to blend in with overall building color, shape, and aesthetic.
Venting material is placed on the metal roofing panels and then covered with ridge cap flashing.
Standard ridge vents are typically 10 feet in length and are common for industrial and agricultural buildings.
These vents are part of the overall building ventilation system and used in conjunction with fans and other building components such as controllable dampers and are potentially able to allow large volumes of hot air to escape.
Gable Vents
Gable vents are often seen at the peak of gables and function as an intake or exhaust method depending on the overall venting system. Gable vents are commonly utilized for residential applications and in conjunction with low profile ridge vent solutions.
Intake Venting
In addition to gable vents, soffit and drip edge vents can also function as intake vents for both ridge and gable vented systems and are designed to bring in cooler air, pulled in as the hotter air leaves the building through the vents above.
For your metal roof project make sure you ask your contractor how they plan to adequately ventilate your roof. A properly installed and ventilated metal roof will last for decades and will provide you with safe, healthy, and efficient residential roof solution.
Many thanks to ProfileVent for their help with this post and for allowing us to use the video.
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About McElroy Metal
Since 1963, McElroy Metal has served the construction industry with quality products and excellent customer service. The employee-owned components manufacturer is headquartered in Bossier City, La., and has 14 manufacturing facilities across the United States. Quality, service and performance have been the cornerstone of McElroy Metal’s business philosophy and have contributed to the success of the company through the years. As a preferred service provider, these values will continue to be at the forefront of McElroy Metal’s model along with a strong focus on the customer.
Topics: Residential
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