A Reminder on the Importance of Roof Ventilation

Proper ventilation for a home involves a measured balance of air intake and exhaust to move air throughout the structure

By Malarkey Roofing Products

Asphalt roofing shingles are designed and engineered to beautify and protect a home. The shingles and underlayment are part of the roof system that limit the impacts of weather on the structure. Shingles and underlayment act as a protective membrane, much like wearing a waterproof jacket, but require ventilation from heat and moisture. According to Dr. Joseph Lstiburek of the Building Science Corporation, without proper ventilation, a reduction in shingle service life from the shingles can result.

What does ventilation do for a home? Roof ventilation controls moisture through an attic, ensuring the space is cooler in summer and drier in winter. Improper ventilation can cause ice dams to form at the eaves in the winter. Ice dams cause roof runoff to backup behind the ice dam and seep underneath shingles and fascia boards. Once this moisture enters the home, several problems can occur.

For instance, homeowners may encounter damage to interior and exterior walls, peeling paint, and cracked ceilings. If ignored for a prolonged period, moisture gain on building materials can also compromise the integrity of the roof structure itself. Likewise, houses have become more tightly sealed and insulated in recent decades, according to Malarkey Roofing Products Vice President of Technical Services Eileen Dutton, in a past issue of RCI Interface Magazine. Coupled with dishwashers, dryers and other moisture-producing appliances, conditions for mold-growth can be prevail.

Poor airflow can produce excessive heat in the attic in summer months. The buildup of heat can create attic temperatures as high as 140°F on a 90°F day. Eventually, this heat moves into the living spaces and causes fans, refrigerators, and air conditioners to consume more energy to keep the home cool.

How does the ventilation system work? Properly ventilating a home involves a measured balance of air intake and exhaust to move air throughout the structure. To establish a steady, high volume airflow, ventilation system components must be properly sized and placed. Natural or mechanical features can provide sufficient airflow. Air intake vents pull cool air outside to move into attic spaces. The vents should run along the roof's lowest eave and for soffit vents, be placed as far to the outside edge of the soffit as possible. Exhaust vents push air through the attic by allowing warm air to exit the attic at a higher elevation. Exhaust vents are placed above intake vents, often near or at the roof ridge, letting natural convection to occur. There are also specific codes and guidelines for how much airflow is required in certain structures.

Learn more about Malarkey Roofing Products at www.malarkeyroofing.com.