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All About Attic Ventilation

September 16th, 2022 | 6 min. read

All About Attic Ventilation

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You put shingles on the roof to keep out the elements, right? Then why do roofers tell you to let air flow through your attic, no matter the time of year?


Look, we get it. Here at RoofCrafters Roofing our clients ask us about their attic ventilation all the time. For over 29 years we addressed their concerns and answered their ventilation questions.


The answer is quite simple. While you want your home to be weather-tight, you don’t want your attic to be airtight. If your attic couldn’t breathe, it would trap both heat and moisture, neither of which is good for the roof or the contents contained there. Far from reducing the heat stress on your home, an airtight attic would work like a balloon by expanding in the summer and contracting in the winter. This in turn would undermine your roofing system and inevitably spawn leaks. 


If you’ve ever wondered about attic ventilation, in this article, we'll explain a thing or two.


How does an attic breathe?


While your attic has neither lungs nor gills, it does indeed breathe. Intake vents located under the eaves allow fresh air into the attic. Intake vents are usually installed in the soffit either individually or as one continuous unit that runs the length of the soffit. Gabled roofs may have vents located on the side of the house, within the peak of the gable. Exhaust vents located atop the roof allow hot air to escape the attic. Known as passive ventilation, this system promotes air exchange. 


roof ventilationExhaust vents come in three varieties:


  • Static vents

  • Ridge vents 

  • Powered vents


Static vents often protrude from the roof like metal mushrooms, due to the covers that are meant to exclude precipitation. Some static vents contain wind-powered blades meant to suck the air out of the attic any time the wind blows.  Like the whirlybird shown below.


whirlybird roof vent


Ridge vents are a little harder to see since they run the length of the roofline. This type of exhaust vent works by leaving a screen-covered gap in the sheathing that runs along the ridge.  This vent allows the heat in your attic to escape naturally. With heat rising and these vent positioned at the peak of the roof. 



Powered exhaust vents use electricity to power an exhaust fan whenever the temperature inside the attic reaches a preset limit. By setting a thermostat inside the attic the fan comes on and off without manually turning the switch. Power attic fans are rated to pull out so many cubic feet per minute. To keep from adding to your electric bill, some of these units are solar-powered.


Power attic fan on a roof



As a rule, your attic should have 1 square-foot of vents for every 300 square feet of attic space. 


Why does an attic need to breathe?


Well it does depend on what type of insulation your attic has. If you have open cell or closed cell insulation it doesn't. If you have conventional insulation it does. And there are three reasons why air needs to flow into and out of your attic. 


First, if hot air gets trapped in your attic, it will add to the amount of time your home air conditioner needs to run in the summer. This will not only cost you more when you pay your utility bills, but it will also reduce the life of your home’s HVAC system. 


Second, without adequate ventilation, condensation can occur in your attic. This can lead to several problems, including mold, and damage to the attic insulation, not to mention potential damage to your roofing system and supporting timbers. The number one cause of roofing materials failing prematurely, you guessed it, is poor attic ventilation. 


Third, for the northern regions, trapped heat in the attic can cause snow, ice, and frost to melt only to refreeze along the eaves, potentially undermining the shingles, tile, or metal that are attached there.


How can you tell if your home’s attic is improperly ventilated?


walking roof with poor ventilation

The first sign of inadequate ventilation would be an uptick in your utility bills. If your electric bill suddenly went sky high or your home’s heating and/or air conditioning system seems to be running non-stop, your attic ventilation may have been compromised.


This can happen in several different ways. The vents could be clogged with dust or debris. This is fairly common in autumn when the leaves are falling from the trees. It’s also possible that squirrels or other wildlife decided to build a nest on or inside one of the attic vents.


How often should you clean out your home’s attic vents?


If you want to maintain the optimal efficiency of attic ventilation, it’s a good idea to clean out the attic vents once a year. This can be done by using a can of compressed air to blow out dust, dirt, and loose insulation that can compromise ventilation by partially clogging the ridge vents. Soffit vents are best cleaned out with a broom. You may need a vacuum to clean out-static vents, although you may first have to remove the cap. Before you turn on the vacuum, take the time to inspect the vent with a flashlight to look for any obvious obstructions. If there are a lot of leaves or a nest blocking the vent, you don’t want to suck that into the vacuum since it could clog it. If you can’t get your hand down the stack to remove a clog, try using ice tongs. 


Attic Ventilation Takeaway


As you can tell now, your attic ventilation is one of the most important components of your property. Inadequate ventilation can cause havoc and unnecessary damage. Having the right ventilation along with enough will surely improve the efficiency of your roof and lower your utilities.


If you have any questions or concerns our family at RoofCrafters Roofing has assisted thousands of homeowners over the last 3 decades. We've helped them by answer their most challenging ventilation questions. We'd love to help you. To get an onsite ventilation assessment Schedule your inspection here. 


For more information about the types of ventilation and the importance of a proper roof ventilation system, read: What You Need to Know About Roofing Ventilation Systems.