Vented or Unvented: Answering the Attic Question


When it comes to venting your attic, there’s a lot of contradicting information. Some will say it’s a waste of money and will do more harm than good, while others say venting is crucial no matter what climate you live in.

If you’re going to vent your attic, the key is executing it properly. Time and time again, poorly constructed attics lead to issues such as ice dams, mold, rot and extreme energy loss, sucking up time and money.

It’s important to understand exactly what the purpose of venting is, the pros and cons of venting your attic, and whether it’s the right decision for you.

Venting in Hot Climates

In hot climates, the primary purpose of ventilation is to rid hot air from the attic or roof to the reduce the building’s cooling load. It also helps alleviate strain on you air-conditioning unit.

Venting in Cold (Dry) Climates

The purpose of ventilation in cold climates is to avoid ice dams created by melting snow and to vent moisture that moves from the conditioned living space to the attic.

Venting takes on either role in mixed climates, depending on the season.

Pros of Venting the Attic

When constructed properly, vented attics serve a number of purposes and benefits. In the winter or colder climates, a natural flow of outdoor air keeps the attic cold, reducing the potential for ice damming, and in turn, roof damage. In the summer and places with hot, humid climates, vents move hot air out of the attic, protecting roof shingles and removing moisture. If you have asphalt shingles left unvented, they are likely to heat up, reducing the service life of the shingle.

Cons of Venting the Attic

Sometimes when attic venting is not executed properly, in hot, humid climates, moisture is brought into the structure. If indoor humidity is high and the air leaks into the attic, moisture problems can develop this way as well. In cold climates, it may allow snow to blow in. Attic and roof assemblies are also becoming more complex, with designs such as skylights and multiple dormers. This makes it harder to construct vented assemblies.

If you do vent your attic, you can’t use it as a living or storage space. Venting will be most efficient if there isn’t anything in the attic except for insulation and air. The attic also has to be air-sealed in order for it to work properly. Vented attics should also be coupled to the exterior, isolated from the conditioned space.

To Vent or Not to Vent

Whether or not you vent your attic depends on a number of factors, including the design of your home, the climate you live in, whether your attic is air-sealed, and the type of shingles on your roof. When properly executed, vented attics have many benefits, but too many times, the process is screwed up over and over again.

Do you have a vented attic? What are the pros and cons you’ve come across?