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The Importance of Roof Ventilation

Malarkey shingles are designed and engineered to beautify and protect a home. As part of the roof system, the shingles and underlayment limit the impacts of weather and exterior elements on the structure. Much like wearing a waterproof jacket, shingles and underlayment act as a protective membrane, but require ventilation from heat and moisture beneath. Without proper ventilation, many problems can arise, including a reduction in service life from the shingles themselves, according to Dr. Joseph Lstiburek of the Building Science Corporation.

Why ventilate?

A primary purpose of roof ventilation is to control moisture through an attic, ensuring the space is cooler in summer and drier in winter. Without proper ventilation during the summer, poor airflow can produce excessive heat in the attic. 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.

In the winter, improper ventilation can cause ice dams to form at the eaves. 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 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.

Intake and Exhaust

How does ventilation 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 encourage the cool air outside to move into attic spaces. The three most common types of air intake vents are eave, individual soffit, and continuous soffit vents. 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, on the other hand, cause outside air to move through the attic. These vents allow warm air to exit the attic. Exhaust vents are placed above intake vents, often near or at the roof ridge, to allow natural convection to occur.

There are also specific codes and guidelines for how much airflow is required in certain structures. These decisions and adjustments are best left to professionals.

Who to call?

To determine the necessary amount of venting for their residence, homeowners are advised to seek consultation from an HVAC professional and a roofing contractor. Malarkey recommends homeowners select a certified contractor to assist with their roofing projects.