As I’ve mentioned here before, I live in a 40 year old condo that’s a good example of what happens when you build something without understanding the principles of building science. I’ve previously written about the crawl space problems in one of our buildings and the basement problems in my building, as well as my proposed remedy to fix the basement. I’m on the board of our owners’ association and am doing what I can to make things better here, to the extent that our budget allows.
Recently, one of our owners had a problem with their dryer not venting properly, and that led me to go around and look at the wall caps on most of our buildings. All the buildings with 2 bedroom units in them have dryer vents that exit through the back wall. The photos above and at right (the same vents from two angles) are typical of what I saw on my tour.
That’s two dryer vent wall caps side-by-side. The one on the left is crushed so the flapper has almost no space to move. The one on the right seems to have no flapper. Both have little space for air to move out of the duct when the dryer’s running, and also don’t do a good job of stopping outside air – and critters – from getting into the dryer vent when it’s not running.
Restricting the air flow in a dryer vent causes several problems:
- The dryer runs longer.
- It uses more energy.
- Lint can collect in the duct, and the duct gets hotter. This creates a fire hazard.
The more restricted the air flow, the more extreme those problems will be.
The good news is that the solution is simple. All you have to do is replace the wall cap to improve air flow, cut drying time and energy usage, and reduce your fire hazard. The photo shown at right is from the other side of the same building where I took the above photos. You can see that both flappers are closed, and both have plenty of room to open widely to enhance air flow. Wall caps are only a few bucks and even if you pay someone to install it for you, it shouldn’t set you back too much.
Of course, the wall cap is probably only part of your dryer’s air flow problem. As with just about any duct system, the duct between the dryer and the wall cap probably has crimps, kinks, sharp turns, and extra length that all cut down the air flow, too. If your wall cap looks like the one at top, though, fix it right away.
See the followup to this article: 4 Products for Enhancing Air Flow in Dryer Vents.
Allison A. Bailes III, PhD is a speaker, writer, building science consultant, and the founder of Energy Vanguard in Decatur, Georgia. He has a doctorate in physics and is the author of a popular book on building science. He also writes the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.
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