What is the best, most permanent and water resistant way to install a range hood wall vent through existing aluminum siding? The siding is installed over housewrap, housewrap is directly over plywood sheathing. My brother-in-law says to trim siding as large as outside of vent mounting flange, screw vent mounting flange directly to plywood, (behind housewrap?) and trim cut edges of siding with aluminum j-channel. The guy at Home Despot says no, just cut a hole as big as the ductwork, screw right through siding, and fill gaps between siding and vent flange with gobs of silicone. Complicating things, I read an article online (I know- never believe anything that you read online, except DIY.com) that says to NEVER use j-channel outside- it is purely cosmetic and actually directs water BEHIND the siding.

 

Cutting the hole just the right size and using sealant (I'd use Quad or Vulkem) is probably your best bet.

If the vent was being put on at the same time as the siding was being installed (originally) you could do it differently, but since you can't unzip aluminum siding very easily I'd say the HD guy is steering you in the right direction.

 

Thanks! I was not relishing the thought of trying to unzip the siding. Perhaps I will cement a piece of flashing under housewrap at top edge of vent for a little extra protection.Beer 4U2