Attic Ventilation Crash Course

As construction technology has progressed, an increased focus on proper attic ventilation has become necessary. In most cases, this is due to a focus on energy efficiency - i.e. keeping heat inside your home so your energy consumption remains low. This means new vinyl windows, blown in insulation, and a variety of other improvements. While all this can be great, an unaccounted for side-effect has been overly warm attic spaces and resulting condensation.

If you have ever had a cold drink outside on a hot day, you know what condensation is. The water droplets that collect on the outside of your bottle come from the moisture in the air. As the hot air comes into contact with your cold drink, the air particles condense and are no longer able to carry as much moisture, and so it ends up on your bottle.

The same thing happens in your attic space when the outside temperature is much lower than your attic space. Water droplets will be released as the air in your attic space cools down too quickly, but instead of harmlessly rolling down your soda bottle, it will end up on your plywood and can cause long term damage and mold if not dealt with.

The solution to this problem is to keep your attic space as close to the outside temperature as possible. This is achieved through proper attic space ventilation. As the hot air in the attic rises and exits through the roof vents near the peak of the house, cool air will be drawn in through the low side of your ventilation system closer to your gutter line. If designed properly hot air will be continuously displaced by cool air, keeping the overall temperature of the attic down and reducing the risk of condensation related issues.

Common Causes of Ventilation Failure

1. Improperly Designed System: Everything comes down to math. There is a simple equation that will tell you your ventilation requirements to allow for adequate attic cooling. If the math does not add up, then you will likely be caught with a condensation issue.

2. Improperly Blown-In Insulation: Insulation can block off the low (intake) side of your ventilation system if baffles have not been set in place before the insulation was blown in. If these vents are blocked off, outside air will not be able to enter, making for a very warm attic space. A quick test you can do is to go into your attic space and turn off the lights. Look around and see if you can see light coming in through your eaves. If not, your intake vents may very well be blocked.

3. Energy Efficient Upgrades: This can be new windows, new doors, sealing the cracks in your siding, etc. Whatever the upgrade, the idea is to keep the heat in your home and not out the window. While this can be an amazing experience when you go to pay your heating bill, you should also consider the effects these upgrades may have on your attic space. All that heat that used to leak out of the windows has to go some place, and that place is likely to be your attic. Older, less energy efficient houses may have been able to get away with inadequate attic ventilation. But if suddenly that attic space is made substantially warmer, the old ventilation system may not be enough to cool down the area. Again, this can result is condensation, dry rot, mold and premature shingle failure.

We are not here to discourage you from making improvements to your home, and we are not trying to make you paranoid! We simply want to encourage you to stay informed to the condition of your house. Many extreme circumstances caused by inadequate attic ventilation could have been avoided if the problem was caught early on.

If you think you may have a ventilation issue, we are happy to come out and take a look.

To learn more about roof ventilation, check out this article from the International Institute of Building Enclosure Consultants: https://iibec.org/attic-ventilation-101/

Frequently Asked Questions

Q: Should I put ridge vent on my roof?

A: The short answer is that it depends. While ridge vent has become very popular, it should not be used in every situation. The objective of an attic ventilation design is to achieve what we call a Balanced System. This means that the amount of exhaust ventilation (vents near the top of the house, including ridge vent) should match the amount of intake ventilation (vents closure to your gutters, like soffit vents or bird blocking).

Installing a new ridge vent will usually dramatically increase your exhaust ventilation. If the adjustment is not made on the intake side of the system, this can actually cause more problems than it solves. Every house should be treated as an individual case - just because a product is trendy does not mean that it is the right thing to install on your roof.

Q: Will you add more soffits vents if I don't have enough intake?

A: Adding more soffit vents is one way of solving an intake problem - but as roofers, we like to stay on the roof! The benefit of using intake roof vents is that they are much less likely to be covered by blown in insulation or painted over.

Q: Do you install attic fans?

A: Yes we do. An attic fan can often do wonders to cool down the attic space. But again, there is no one-size-fits-all solution. If installing one is something you are curious about, make sure and ask us about it and we will walk you through making the best decision for your roof.

Q: The plywood in my attic is turning black! Do I need a new roof?

A: It all depends on the extent of the damage. In many cases, mold and mildew can be treated without replacing your roof, though you definitely want to fix the ventilation problem that caused it.

In other situations, the condensation has gone on for too long, and a roof replacement is necessary along with the replacement of any roof decking (plywood/OSB) that is damaged from the problem. If your plywood is discolored and you feel soft spots while walking on your roof, it is likely time to replace your roof.

Q: Will improper ventilation reduce the life of my shingles?

A: Yes. If signs of condensation are observable in your attic space, this means that the plywood has been exposed to water. When wood absorbs and releases water, it will swell and shrink. This movement can cause your shingles to pull against themselves causing premature degranulation, and a shortened roof life.

Because attic space condensation has become so prevalent in recent years, manufacturers warranties are significantly reduced if an attic space is not properly ventilated.