Sealing suggestions for Drywall + 4" duct

Hi everyone hope all is well..

My situation is.. I will be having a 4" duct pass through interior drywall and exterior particle board. I will need to cut drywall and particle board so the duct pass through. I've read some previous posts and I think I want to make the cut with a keyhole saw (does anyone agree?)

My question is.. what is used to seal the duct and walls? Chalking? Do I need different sealers for drywall and particle board? Any suggestions would be greatly appreciated. Beer 4U2

 

I'd use a 4" hole saw on a drill. And besides the location of the studs, consider the placement of the duct on the siding (on the outside) before selecting the exact location for your hole. Usually it works best when you have lap siding if the duct does not fall right on the "hump" of 2 rows of siding. You might want to move it up or down a little to make life easier. A small 12" long drill bit (1/8" or 3/16") works well to drill all the way through the wall... marking the location of the hole on both sides of the wall at the same time. Make sure there are no electrical wires in the wall where you are drilling!

As far as sealing is concerned, it works well to cut a piece of fiberglass that will fit into the wall cavity... such as a piece that is 14 1/2 x 14 1/2. Cut a 3 1/2" hole where the duct will be located, and stuff the fiberglass into the framing. By cutting the hole a little smaller, the insulation will fit snug as you slide the duct through. Then a siliconized acrylic latex caulk would probably work well for both sides of the wall, since it is paintable. Some dryer vents come with a ring (like a 4" washer) that you can slip over the duct to cover up the rough edges of your drywall.

 

Thanx for the info XSleeper..

Sorry, I'm a little new to this... the fiberglass.. it's real flexible like cloth, right? Should I wrap the fiberglass around the duct or just stuff it in with it clumped up in one area? Should any fiberglass be left outside the walls for the sealant?

Thanx!

 

No worries, we're here to help! Fiberglass is usually yellow... 3 1/2" thick, 14 1/2" wide, and comes in long pieces called "batts"... about 92 5/8" long, and yes, I guess you'd say it's flexible. What I was suggesting, assuming your wall already has some insulation in it... was to just cut a small square (such as 14 1/2 x 14 1/2) that would fit between your studs. Bunch it up so you can shove it into the wall through the 4" hole you cut. (so the hole is now completely blocked by the fiberglass insulation.) Flatten it out inside the wall as best as you can so that it isn't all bunched up. Then cut a 3 1/2" hole through the insulation. Since the insulation is a bit spongy, you should be able to shove the 4" duct through that hole, and it should fit nice and snug. Your insulation will be INSIDE the wall, no need to pack anything around the outside edges of the duct. That's where your caulk will go.

 

just to clarify...dasmo is thinking of fiberglass mat..as is used for body repairs on vehicles and boats. X is talking about fiberglass insulation as is used in houses.

 

Ok, Gotcha. That cleared things up quite a bit.

Thank you for your time, XSleeper. And Gunguy, thanx for the clarification