Whether you vent a garage roof or not is choice but generally speaking, it’s a good thing to add a vent to a garage. Most garages are not heated but a vent is made to vent out moisture in the winter and heat in the summer.
Most municipal codes do not require vents and if you have an attached garage (attached to your house), sometimes there is an aesthetic reason to skip the vent. However, the pros outweigh the cons.
Here’s why you should consider having a vent:
- Heat build up hurts longevity: A vented garage roof will allow heat to escape. This is especially important in hot weather months and will prevent shingles from breaking down prematurely.
- Moisture is unhealthy: A vented garage will allow moisture to escape. In cold weather climates and climates that have a lot of rain, moisture can build up inside of a garage and can result in mildew or even mold on the inside.
- Moisture can damage concrete flooring: If your floor doesn’t dry as fast as a well ventilated area could, water that freezes between cracks will expand and will prematurely damage your floor.
Even a single vent on a garage can help keep a garage cooler in the summer and vent out moisture in the winter
Today I received a call from a customer who was concerned that their garage would be too cold in the winter now that we had installed a vent in her garage. Previously her garage did not have a vent. I explained that a vent was beneficial to her. Still, she insisted, it would make it colder, would it not? Well the answer is yes, it will make it so that her unheated garage will lose heat quicker in the winter. The plus side here is that the shingles will not have as many freeze/thaw events this coming winter and therefore will last longer.
Like shoving unchewed meat in your throat to prevent overeating <bad idea>
She suggested that we should just push some insulation up into the vent to keep heat from escaping. I explained that such a practice would cause more harm than good and we do not recommend closing off vents for the winter. You’re actually causing more problems than you are solving.
“Just cover it up for the winter” <bad idea>
… was her next idea. That’s a horrible idea since car tires and wheel wells have ice and snow on them and that ice and snow melts in garages here in Wisconsin and that snow gets into garage. That moisture needs a place to escape.
Intake ventilation
To understand how proper ventilation works, you have to understand that a roof that is well ventilated has appropriate venting for exhaust, but also must have intake ventilation. On houses that is typically coming in from the soffit so air comes in from under the overhang (the soffit) and exhausts out through the top. Garages are different animals. Many garages don’t have soffits that are as big as on houses and some garages just don’t have soffits. However, a garage doesn’t typically have insulated walls, they leak like crazy from around the doors as well as from any windows. Thermal insulation in an unheated space is typically not the priority of a builder. Therefore, a garage that is very leaky and inefficient acts as a giant intake vent naturally.
Some ventilation is better than none
On a house there are three common types of passive air vents — pod vents (sometimes called turtle vents), slant back vents and ridge vents. Most pod vents and slant back vents vent out about 240 square feet of roof and the average 2-car garage is about 600 square feet. Ridge vent capacity can vary widely depending on materials used, height of the ridge vent (the rise off of the roof) and how clogged the ridge vent fabric has become from dust and dirt. While some ventilation is better than none, keep in mind that none will allow your garage shingles to slow cook over the next 10 to 30 years. Before completely dismissing adding vents, consider how that portion of the roof will look when it comes time to sell your home. Is a short term aesthetic gain worth a roof that might look worn after as little as 10 years? A roof with a southern exposure is going to tend to wear out quicker in countries north of the equator.