[l008com]

This photo is my sewer vent pipe looking up. That hole is where it passes through the ceiling and into the attic. If you look real close, you can see attic up there.

Currently there is zero insulation up there. I'm getting all new stuff blown in. But thats a good size hole so I want to patch it up before hand. They insulation people might be doing that, but in case they don't, I'll just do it beforehand.

Whats the best way to do this? Do I need to leave any space around the pipe at all? I could pretty easily get some thin plywood, cut the appropriate circles in two pieces and nail it in to fill that gap.

 

[jimn]

They actually make fire stop for this kind of situation . It's available as a putty and spray foam. Not usually required in residential but it can't hurt.

 

[l008com]

That seems like too big a gap for spray foam or a putty though, no? Thats like a solid 1.5" by 3.5" gap on the large side of the pipe.

Also I didn't mention it but i also want to cover this up since it's a direct air flow to the outside (via attic vents) and i'm burning through a lot of oil waiting for the insulation to come.

 

[ront02769]

Just go spend six bucks for a can of the orange fireproof spray foam and have at it. It will be fine. If you are worried, grab any thick ness piece of ply or whatever wood you have and just make the gap smaller...but foam everything afterward. Ron

 

[l008com]

I've used that stuff a ton, it drips out of small holes. This stuff is way to big to use that stuff on. All of it will fall through the hole. I think maybe hole looks smaller in the photo than it really is?

 

[Bud9051]

As an energy auditor we advise a lot on air sealing. What you suggested with the plywood is close, we just use flashing. Configure as many pieces as you need so they fit around the pipe and overlap so they can be sealed together. They make a fire rated caulking that, along with the metal flashing provides proper fire protection.

As for the insulation crew taking time to air seal, not a chance unless they are specifically being paid to do so. I'll add a link on air sealing from Efficiency Vermont. You will want to address many locations BEFORE that new insulation goes in.
http://www.efficiencyvermont.com/stella/filelib/TBC_Guide_062507.pdf

Best,
Bud

 

[ChuckF.]

"I could pretty easily get some thin plywood, cut the appropriate circles in two pieces and nail it in to fill that gap."

Yes. Quick work with a jigsaw or sawzall, use no less than 1/2" plywood, screws, and follow up with caulk or foam.

It's possible that all your penetrations are done to that quality, you should spend some time in the attic checking them all.

 

[Mingledtrash]

If you dont want to use foam you can always go old fashioned with some rockwool or mineral wool.

Easiest way is to get a flat roof pipe flashing for the size you need and cut it in half.
also you need a plate strap on the other side of the wall.
http://www.strongtie.com/products/connectors/rps.asp

http://stores.hvacexpress.com/pipe-flashing-with-flat-pitch-3-inch-fp-3/