What Is Attic Ventilation?

There are two sides to every story—but what some homeowners may not realize is that there are also two sides to most roofs, too. Beyond the professionally installed roofing system that protects your house from water on the outside, an attic ventilation system works from the inside to protect your home from heat and moisture.

What Is Attic Ventilation?

Through a balanced system of intake and exhaust vents, proper ventilation lets your attic—and your entire home—breathe. The word "ventilate" originates from the Latin word meaning "to fan." Essentially, ventilation moves hot air out and cool air in, replacing stale, overheated air with fresh air from outside.

How Does an Attic Ventilation System Work?

Hot air rises naturally, so intake vents located at the bottom of your roof under the soffits allow cool air from outside to enter the attic. This fresh air keeps flowing through the attic before escaping back outside through the hot air exhaust vents, which are located on the top of the roof.

This is a natural process called passive ventilation—one of the most common and effective ways to achieve a balanced attic ventilation system. The amount of exhaust ventilation at or near the roof ridge should never exceed the amount of intake ventilation at or near the roof's soffit.

Why Is Attic Ventilation Important?

If your attic is not properly ventilated, the space can reach more than 160 degrees Fahrenheit, particularly in the summer heat. Those high temperatures risk overloading your home's air conditioning system. Without adequate ventilation, a buildup of heat and moisture in the attic can cause your roof system components and structural supports to degrade over time, potentially reducing their service life. It's crucial to release that excess heat.

During the winter months, the hot, moist air in your attic along with the sun, can heat up your roof and melt the snow that accumulates on it. When that running water then refreezes as temperatures dip, ice dams can form on the colder roof edges under the eaves. These ice dams can also cause water to work its way back up under your shingles, damaging the roof and potentially leading to leaks inside your house.

Here are a couple of more reasons why ventilation is so important.