Sealing Gaps into Attic

[msmity29]

I have a question concerning sealing gaps in the attic....I was told I needed to seal, with caulk, the gaps where pipes etc enter from the second floor into the attic. Is this only true on exterior walls or should I seal anywhere a pipe enters the attic? And what about where pipes pass through joists in first and second floor exterior walls (pipes running horizonatally)? Do they need to be sealed too?

[David]

I have a question concerning sealing gaps in the attic....I was told I needed to seal, with caulk, the gaps where pipes etc enter from the second floor into the attic. Is this only true on exterior walls or should I seal anywhere a pipe enters the attic? And what about where pipes pass through joists in first and second floor exterior walls (pipes running horizonatally)? Do they need to be sealed too?

All very good questions. I think I had told you in a post before to seal gaps heading into the attic.

Not with caulk, though. #1 It needs to be a fire-rated substance. #2 In this case, you won't get a great seal with caulk. Here, expanding foam fits the bill well. It'll have a lasting seal and is fire-rated.

It has nothing to do with walls, but everything to do with your conditioned spacing. Your building envelop is the air/water/vapor protection your home has, and it's where you want your conditioned air. Thus, seal all penetrations into the attic. Technicaly, you'd like to seal all penetrations in the drywall, too. Aka, ceiling lights (especially canned lights) and fans. You need to seal off any holes resulting from cable tv, phone, and any other low voltage wires you may have. Yes, these are in the walls, interior and exterior. Does not matter.

And what about where pipes pass through joists in first and second floor exterior walls (pipes running horizonatally)? Do they need to be sealed too?
Water pipes on exterrior walls should have a foam insulator around them. HD and Lowes have 'em, but you SHOULD NOT have to install them. Shame on your builder if the plumber does not install these!

You may want to look into rubber air-tight outlet boxes. I've been in the attic and felt my warm air in winter come right up thru the conduit to a light I was working on.

You should also seal the holes where your conduit penetrates into the attic.

You have lots of work. Be sure you have enough cans of fire-rated expanding foam. You can always take unopened ones back. Work systematically and safe, and not by yourself! Bring lights you can hang from rafters. Your knees will get sore. And, realize this is not just some theoretical practice. You are building a home for your family...do it right and be proud of your efforts.

[Vector]

In MN, and I'm farily certain IL, code requires the use of an "air tight" electrical box on all external walls. It also requires sealing all vertical penetrations with foam or fire-stop rated caulk.

The proper electrical boxes should be installed my the electrician as a matter of course. And generally speaking, the insulation sub will foam all the holes (this varies sometimes, sometimes the mechanical subs are responisble for foaming the holes they create). You should not have to do anything.

Even the cheapest, most cost-cutting, crap house builders I worked with did these things (or they would never pass any framing or insulation inspection).

[David]

My house in NW chicago burbs was built in '94. Air Tight boxes were not required then. Maybe now??

FWIW, air tight boxes should be used on internal walls, too, as air can seep up inside the conduit and find it's way out in the attic. They are supposed to be (almost) completely air tight, so air can't escape up the conduit or out the back. I've never seen one, but plan to use them if I eventually build a place up north. Don't they have rubber flanges to keep air going up the conduit?

As for foaming holes, agreed, this should be done by contractor. However, I think the OP wants to be certain it is done everywhere. Subs may miss spots (*if* they do it), and most inspectors will miss spots for sure.

[Vector]

FWIW, air tight boxes should be used on internal walls, too, as air can seep up inside the conduit and find it's way out in the attic.

That's right, Chicago an the areas around still require conduit in all cases. Typically elsewhere non-metallic cables are used and the holes are sealed at the top with foam, so airtight boxes are not necessary on internal walls.

Using airtights in external walls is for insulation purposes, not fire resistance.

As for foaming holes, agreed, this should be done by contractor. However, I think the OP wants to be certain it is done everywhere. Subs may miss spots (*if* they do it), and most inspectors will miss spots for sure.

The thing is, the insulation contractor generally foams and puts in the fiberglass and vapor barrier all at once, so it's hard to go in and catch anything they missed.

[David]

The thing is, the insulation contractor generally foams and puts in the fiberglass and vapor barrier all at once, so it's hard to go in and catch anything they missed.

Good point.

[msmity29]

Thanks for all the great input! We were out at the house yesterday and someone did seal almost all the holes leading into the attic along with those between second floor and first, and first and basement. I am going to go back and make sure they didn't miss anyway. Thanks again!