Bathroom Exhaust Vent Question
 

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I don't think there is screen inside the duct. There is a spring loaded metal flap above the bathroom ceiling that closes when the exhaust fan shuts off. But, I am not sure if it closes tight enough to prevent wasps from entering the house. I would spray wasp killer into the soffit opening to discourage or kill the wasps, or hire a pest control company to handle the problem. As I understand it, wasps do tend to leave after a few months or so.

I just went through this, in our house and a few neighbors (2013 vintage) there was a screen with maybe 3/16 inch mesh. The wasps were able to get through this and into the house. I and my neighbors were able to remove the plastic covers, install regular screening and replace the cover. This took a few minutes for each cover. No wasps since the change.

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