Knowing the importance of roof ventilation can assist you when considering a roof replacement or making improvements to your home. As the main line of defense against weather of all types, a well-made roof should protect against potential damage from all types of weather. While environments and weather patterns differ in each region, one principle will always remain the same: roofs require efficient ventilation systems.
Even in a securely constructed home with many layers of insulation, air rises through the ceiling to the attic and holds water vapor. Without proper ventilation, the trapped, moist air can condense on the underside of the roof, seeping into the insulation and the roof deck. Once the moisture soaks the roof deck, rot can set in. The moisture may drip into the ceiling beneath, penetrating drywall, cracking plaster and causing slow-growing mold and mildew.
When vents are installed at the eaves and ridge of the roof, it provides continuous air circulation in the attic, from the floor level to the top of the roof. Moisture-laden air joins in with the current, flowing freely to the outdoors, helping to prevent condensation and water damage.
Summer’s Drastic Heat
An enclosed attic in summer weather can reach unbearable temperatures. The trapped heat will affect the overall climate of the home. Your air conditioning system will have to work harder than usual to maintain a comfortable temperature, and your refrigerator may have to work overtime as well. Asphalt shingles are designed to withstand heat, but when the attic adds another dimension to the roof’s temperature, over time the shingles may break down faster than expected.
Winter’s Risk of Ice Dams
While you may associate the word ventilation with heat, the winter season requires adequate ventilation as well. Imprisoned attic heat will cause roof snow and ice to melt even when the outside air is below freezing. As the melting snow drips down the roof, it refreezes, causing an ice dam along the edge of the roof. Behind and underneath the ice is pooling water, sitting on a moisture-sensitive roof deck – a sure way to speed up roof degradation and interior water damage.
What Are the Code Standards of Roof Ventilation?
To ensure adequate ventilation in every home, the International Code Council, the U.S. Department of Housing and Urban Development and the American Society of Heating, Refrigerating and Air-Conditioning Engineers developed guidelines for minimum ventilation requirements.
For every 150 square feet of attic floor, one square foot of net-free ventilation is required. If the roofing contractor installs vents both at the base of the attic floor and at the roof’s ridge, providing equal ventilation, the ratio changes. In this case, one square foot of net-free ventilation is required for every 300 square feet. If a roofing expert concludes your attic does not meet these minimum regulatory standards, be sure to remedy the problem as soon as possible to avoid moisture damage.
If you notice signs of moisture in your attic, schedule an inspection with a local roofing contractor and closely examine your roof’s ventilation system. Understanding the importance of roof ventilation can help you extend the life of your roof and limit the risk of water damage and mold.