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Clean duct and replace cap from outside?

My house has a bathroom vent fan that vents through a side wall. The hooded vent cap doesn't close very well, and birds have gotten in and made a nest.

Is there any way to clean out the vent duct and put on a better cap without cutting open the ceiling of the bathroom? I'd like to just remove the cap, pull out the nest with some tongs (the duct is only 4 feet long), and attach a new louvered cap, all from the outside of the house. I think it's a flexible aluminum duct.

One repair guy has told me, without really looking at the ductwork, that this is never a possibility since there's usually no slack in the ductwork. I'd think that pulling the cap out an inch or two would work. Would this be enough to replace the cap?

Would blowing the nest out from the inside with a leaf blower work?

Re: Clean duct and replace cap from outside?

So I found a contractor who claims he can probably clean out the duct and replace the cap from the outside.

I'd like to replace the cap with another one that has a hood on it, to reduce the change of rain getting inside the wall. But the contractor says hooded caps are no longer up to code in Massachusetts, though he says the code refers more to dryer and gas exhaust vents than bathrooms. He says the new louvered vent will keep the rain out, but I'm concerned that the louvers might not make a rain-tight seal a few years down the line.

Are hooded vent caps really prohibited? I've seen them even in relatively recent construction and renovations. Are there louvered vents for sale that include rain hoods?

Re: Clean duct and replace cap from outside?

Well, the contractor came and made the repairs. He did it all from the outside of the house. It took him about an hour and a half to replace the caps on 3 vents, and clean out bird's nests from 2 of them.

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