This past week I was asked to check out a home because they couldn’t cool their upstairs. When I got there, I didn’t need to get on the roof or even go inside their home to see that they didn’t have any attic ventilation at all.
Having no ventilation caused the heat that was trapped in their attic to burn up the roof system. And now, because it’s burnt up, the whole roof has to be replaced.
The sad part of this story is that the owners had the roof replaced only two years ago. The roofing company they used decided to cut a corner by not adding any ventilation at all. Because the owners didn’t know anything about ventilation, they were unaware of how important it was to their whole house.
Don't let that happen to you. By the end of this article, you'll learn everything you need to know about attic ventilation and how it affects your roof.
And at the very end, don't forget to grab your checklist of questions to ask a roofing contractor to help you find a great roofer to help with your attic's ventilation system.
Proper Attic Ventilation: What is it and why is it important?
Simply put, ventilation is a system that allows your house to breathe. It pulls fresh air through your attic and allows the heat to escape on a constant basis. This constant movement keeps the heat from staying next to the floor of the attic and then entering the area below it.
The amount of air coming into your attic should equal the amount of air leaving your attic. This is called a balanced ventilation system. This air flows in through intake vents and out through the exhaust vents.
Intake vents are located at the lower part of your roof called the eaves or soffits. Intake vents allow cooler air to enter the attic.
You’ve heard that heat rises? This is called “convection.” The cooler air from the intake vents pushes the warmer air up and out through the exhaust vents near the ridge. There are several different types of exhaust vents that I will talk about in a minute.
If your home doesn’t have the proper intake ventilation, none of the exhaust vents will work. If the air isn’t given a way to move around in your attic and for the heat to escape, then damage from heat and cold will shorten your roof’s lifespan and it will also void the shingle manufacturer’s warranty.
The amount of ventilation that an attic needs is different for each home. The square footage of the attic space is what determines how many vents you should have installed. In a publication released by the U.S. Federal Housing authority, there should be a minimum of at least 1 square foot of attic ventilation for every 300 square feet of attic floor space.
Why is proper attic ventilation important in the summer?
In the warmer months, your attic can get very hot. If it’s not properly ventilated, it can heat the upstairs of your home to the point where it’s uncomfortable. It may even get too hot to be upstairs at all during the day, only cooling when the sun goes down.
In the summer, your vents should be pulling in fresh air and allowing the hot air to escape. If the temperature outside is 90°F, the temperature in your attic can get as high as 170˚F.
If the temperature inside your attic is 170˚F, then the heat at your attic floor can be as high as 140˚F. The temperature in the rooms below your attic will be uncomfortable. Your AC will have to work harder to try to keep your home cool which will cause your energy bills to rise.
Poor ventilation in the summer can cause heat to build up in your attic which in turn burns your roof up. The roof decking can delaminate quickly. This means the adhesives in the decking has deteriorated and causes it to become brittle. It also causes your roof’s shingles to become brittle, crack or curl.
Making sure your attic is properly ventilated will help you get the full life out of your roof.
Why is proper attic ventilation important in the winter?
When I tell people that proper ventilation is more important in the winter than it is in the summer, they are always surprised. What most people don’t know is that heat and moisture from the home’s interior travel into the cold attic, which causes condensation and all the problems that can come with that.
Condensation collects on the underside of the roof which then causes the decking to swell. If the decking holds onto this moisture, it will become wavy. If the decking is wavy, guess what? Your roof will also be wavy!
Because the decking is wet, over a short period of time, it will also lose its ability to hold the nails and may lose its load bearing capacity. This can also cause mold and mildew which can contribute to serious health issues.
Plus, moist wood rots. And insects such as termites love moist, rotting wood.
What are the types of attic ventilation?
There are two types of ventilation systems, active and passive. Active ventilation means the air is pulled in from the outside and pushed out from the inside. Passive ventilation means the air in the attic is moved by natural sources, such as wind.
Active attic ventilation
An active roof ventilation system working year-round is the life of your roof. It creates a drawing effect on the air. They pull air from the intake vents and push it out through the exhaust vents. Some types of active vents are:
Turbine Vents (Whirlybird). Turbine vents are really great in that they have a drawing effect through convection (heat rising) even when there is no wind. Properly sized, they exchange the air in your attic 10-12 times per hour. Shortly after the sun goes down, the air inside the attic is the same temperature as the air outside.
I’ve been installing turbine vents for over 30 years and there is a myth about these vents that I’d like to clear up. Since turbine vents have slats on them and are open-aired to the attic, there is a misconception that rain, snow, and insects can enter your home through them. However, they are designed so that none of this occurs, contrary to the myth. Unless the vent is damaged (such as a tree falling on it), it works beautifully without any intrusion at all. If mounted properly, you will not see the vents from the front of your house.
Power vents. These vents are the circular-shaped vents with very low profiles you see on roofs. Placed near the ridge of the roof, they use electricity to pull the hot air from the attic. Power vent motors have a tendency to fail so be prepared to replace them at some point.
There are a lot of homes that have power vents installed. Be aware that if you run a power vent in the winter, you’ll want to run it with a humidistat. Otherwise, the humidity will build up in your attic and cause condensation, which is never a good thing as we’ve discussed in this article.
Ridge vents with a baffle. Ridge vents are very popular because they aren’t noticeable from the ground. They are cut into the ridge of the roof and run the length of it. If a ridge vent doesn’t have a baffle to help with airflow, then it is a passive vent. A downside to this vent is that if the vent doesn't have a filter, insects, debris, rain, and snow can enter the attic.
Solar powered vents. Solar powered vents are like power vents, except they use the sun as their power source. From an energy saver standpoint, these vents sound great, but the problem is that when the solar powered battery is charging, it turns off. The solar panel won’t hold a charge long enough to run the vent all day due to the power needed to run the motor. So while the battery is recharging, you may wind up with your air conditioner running more which will cause your energy bill to go up.
Passive attic ventilation
A passive roof ventilation system uses the natural forces of nature such as wind and convection to move the air through your attic. It has no moving parts, creates no noise and is virtually maintenance free. Passive vents include:
Static vents, also known as Turtle vents or Box vents. These vents are little boxes on your roof and are vented to allow the heat to escape out of the roof through the convection method.
Ridge vents without a baffle. As I said earlier, ridge vents are cut into the ridge and run the length of it. Ridge vents without a baffle will allow debris, rain, snow, insects, etc. to enter your attic.
Gable end vents. A gable end vent is that wooden vent we’ve all seen at the ends of houses at the steep part of the roof.
What are signs of poor attic ventilation?
It’s easy for you to check your own attic to see if it has ventilation. But it may take a reputable, qualified roofing expert to see if it has the required vents to properly ventilate your attic space. Most home are not properly vented. Here are a few signs that you have a poor ventilation system:
Stains on your ceiling
Excessive heat upstairs
High energy costs
Peeling or blistering paint on your walls or ceilings
Rust on the metal components of your roof from excessive moisture
Damage to siding
Mold and mildew
Do you think your attic isn't properly ventilated?
There should never be a poorly ventilated attic. Sadly, it is very common in North America. If you think you have improper ventilation, you may want to do some research to find a qualified, reputable roofing contractor to do an assessment on your attic and roof.
When looking for a potential roofing contractor you need to ask the right questions and get the right answers back to figure out if they're a reputable roofing company. Luckily, we have a checklist that does just that.
We here at Bill Ragan Roofing use our highly trained team of roofing experts to help people with their attic ventilation for over 30 years. We take pride in our award winning service and our customers trusting us.