Why a dryer vent must not have a screen on it
Can a dryer vent have a screen or cage on the outside?
A dryer vent must not have a screen, mesh, or cage over its termination. This is not a preference — the International Mechanical Code (IMC 504) prohibits it, and the reason is straightforward.
Why a screen blocks the vent
Everything a dryer pushes out of the duct is lint and moisture. A screen is a grid of edges sitting directly in that stream, and lint catches on edges. It does not pass through and it does not fall off. It accumulates until the mesh is a solid mat and the outlet is closed.
The failure is quick, and from inside the house it is invisible. The first thing anybody notices is clothes that will not dry.
Why they get fitted anyway
Almost always to keep birds or rodents out — which is a real problem, and a screen is an understandable response to it. The trouble is that it trades a seasonal nuisance for a permanent restriction, and it does not solve the original problem especially well either.
The right answer to an animal getting into a vent is a proper hood with a flap that opens under airflow and closes when the dryer stops. That excludes animals precisely because it is shut whenever the dryer is off, and it does not obstruct the outlet when the dryer is on.
What we do when we find one
We tell you, and we show you. Replacing a screened or failed cap with a proper flapped hood is a flat $225, and it is one of the more satisfying repairs to see before and after — the run goes from no visible daylight to a clear line of sight.
If you would rather not have it replaced, that is your call. We will still tell you what we found and why it matters.
Last reviewed Sunday, August 30.
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