Proper attic ventilation is an important aspect of any roofing system and it serves many functions for your home. It can help regulate temperature throughout your home, keeping your family comfortable all year long, and by reducing heating and cooling costs, but even more importantly, good ventilation ensures that the internal components of your roofing system remain dry.
How Attic Ventilation Works
Effective attic ventilation usually includes intake vents along the soffits, and exhaust vents at the peak or roof ridge. This allows for a continuous flow of air through the space from low to high.. Cooler air gets drawn in through the soffit vents, and warm, humid air migrates to the peaks and exits through the vents along the roof ridge.
Why Adequate Roof Ventilation is Important
Proper ventilation in your attic helps address excess heat and moisture that can otherwise wreak havoc on your home. Heat and moisture buildup in an attic can cause different problems in both hot and cold climates. People who live in areas with hot summers and cold winters can suffer the effects of both issues and are most in need of a good roof ventilation system.
During the spring and summer months, the sun beating down on the roof can increase the temperature in the attic. This excessive heat can warp the roof sheathing and distort and age the shingles prematurely. If the attic floor isn’t properly insulated, that heat can radiate down into the living space causing your AC unit to work overtime.
In places where the temperature drops below freezing during the winter, warm air can escape into the attic from the heated living space below, and rises up to the underside of the roof deck. As the roof deck warms, the bottom layer of accumulated snow on the rooftop begins to melt, causing water to run down the roof. Once the runoff reaches the cold outer edge, it refreezes into ice. When this happens repeatedly, an ice dam forms along the eaves, blocking the escape of further runoff. Once the water has nowhere to go, it can back up under the shingles. A properly installed self-adhered underlayment is a final defense against ice damming. This tear-resistant, waterproofing product seals tight around nails. It helps prevent water overflow from entering exterior walls or the attic where it can saturate the floor insulation, ruin the drywall underneath or get into the interior walls.
Humidity, generated from your living area or from outside, that enters a cool attic condenses into a liquid when it meets colder surfaces. Over time, that moisture can cause deterioration of the roof system and interior structural elements or ruin the attic insulation. In a warm attic, the moisture can allow mold and mildew to flourish and put added strain on the home’s cooling equipment.
Spotting the Signs of Improper Ventilation
An inadequate attic ventilation system can cause a variety of problems that manifest themselves in different ways.
Here are some things to watch out for:
- An increase in your household heating and cooling bills, which can happen if your attic insulation gets wet and loses its effectiveness.
- More frequent HVAC repairs as heating and cooling equipment that’s under a heavier workload can become more prone to breakdowns or even premature failure.
- A noticeable buildup of ice along your roof edge during the winter months.
- A wavy or rippled appearance to your home’s roofline and shingles that’s caused by warping of moisture-damaged decking underneath.
- Rust and corrosion on metal materials in the attic, such as nail heads, electrical boxes, light fixtures, and HVAC system components.
- Dampness, water stains or frost on the attic side of your roof sheathing, or any evidence of deterioration and decay of the roof’s structural supports.
- An increase in discomforting allergy symptoms or respiratory illnesses among your family members, which may be related to the spread of fungi spores through your indoor air supply from mold growth in your attic.
How to Address a Poorly Ventilated Attic
If you notice or have suspicions about any of the warning signs listed above, it’s wise to have your attic inspected by a certified roofing contractor who can assess whether there’s enough ventilation for your specific environment and climate zone.
A certified roofing contractor will take various factors into account during an inspection:
- The local climate in your area
- Your roof’s architecture
- The age of your shingles
- The condition of the decking and other roof components
- Whether your attic floor is sealed and well-insulated
If your roof is getting close to the end of its lifespan, or the decking or other components are damaged or deteriorated, repairs or a replacement may be recommended along with the following steps to properly ventilate your attic:
- Installing continuous soffit vents along the outer edge of the eaves
- Adding a ridge vent.
- Insulating along the top plates to meet or exceed the R-value already in the walls.
- Sealing the attic floor to make it airtight, and making sure there’s the recommended R-value of properly-installed insulation in place and that it doesn’t block the soffit vents.
- Allowing one to two inches of air space between the installed insulation and roof sheathing.