Best way to insulate around pipes and cracks in my attic?

[tariskat]

Hi friends,

I've been putting down 2 layers of r5 insulation, the pink thick board kind, on the floor of our attic because it didn't have any insulation (just some cardboard on the roof in front of the shingles.  r10 has to be better than nothing, is my thought; we (for now) aren't blowing insulation because we'd lose a lot storage space.

There are two big pipes that vent to the roof.  One connects to the vent thingy over the stove (which doesn't even work) and is extremely thin metal.  One looks super thick, like cast iron, and it's over where our bathrooms are so it might be connected to that.  The thick pipe is covered in frost, and has clearly melted a few times, since there's water drips all over the insulation below it.  There is also a chimney, which might vent our heating system, which is a pretty standard brick chimney.

My question for you all is, what's the best way to fill in the gaps and cover the pipes that stick up? I don't want to leave the pipes naked, and me being a fairly amateur insulator, there are small gaps left over after I tetris pieces in around various 2x4s and the chimney and the pipes.  I've attached a few pictures.

I was thinking the fluffy pink batts for around the pipes, until I saw the one that frosts/defrosts, and some sort of expanding foam for the cracks between the insulation boards.

Hope you have some advice!

[Greg]

Normally best practice is to insulate ventilation ducts (the thin metal one) to prevent condensation where warm moist air meets cold duct.  This can rust out the duct on the inside.  You can use fiberglass or foam for this.  If it were me I'd fix the fan. :)

The thicker pipe is the main plumbing vent for the toilets, etc.  No need to insulate it.  Frost on the outside of this pipe in the attic could indicate a fairly high level of moisture in the attic, so more sealing of ceiling penetrations in the rooms below, as well as around wires and pipes where they enter the attic especially in upper wall plates is a good idea.

Spray foam in the joints of your insulation panels should work well.

[Cromacster]

Great stuff Expanding spray foam is good for larger cracks.  If you have "hot" items (recessed lighting, chimneys, furnace stacks) that need sealing its best to build a sheet metal box around it and seal it with high temp silicone.  I know they make special insualatino for wrapping pipes.  The insulation should prevent the frost/condesation.

As for the Attic:  What is under the foam board you are putting in?  Is it just the drywall?  I wouldn't store anything on there.  And the foamboard is pretty expensive isn't it?  Much more expensive than some loose cellulose insulation.

Personally, I would blow in insulation then put flooring system on top of blown insulation if you want to use it for storage.  Or you can blow more insulation on top of the flooring and just partition off a section used for storage.

Whatever method you choose, the most important part is the air sealing around any entries into the attic.  Wires, pipes, chimney, lighting.  Seal everything you can find.

[tariskat]

Fiberglass or foam for the thin metal pipe, check.  I'll leave the massive pipe alone, then.

And yes, fixing the fan is next on the list of things to do, I'm just tackling one thing at a time :)

As far as I can tell there are no hot items in the attic; there's a single bulb that hangs up there and it's not close to anything so I can leave it alone.  Re the floor of the attic, you maybe can tell from the picture of the thinner pipe.  Think hardwood floor only no one bothered to sand it down and seal it.  It's not exactly rough cut lumber but it's a solid enough floor. 

Re the foamboard, I got it half price because it was used, spent 300$ for 60 8x6 sheets.  It was used for spacing on a huge physics project and not really insulation so it's like-new materials, which seemed like a cheap enough fix for now.

I like the idea of partitioning off a part of it for storage and adding more insulation to the rest. We could do that for a lot of it and use the center (with the peaked roof tall enough that SO can walk without hitting his head) and throw down in the corners of the house.  The ceilings are high in this house, so the corners of the attic are incredibly cramped.

Thanks for the info!

[tariskat]

We have a new fan on order, no worries there.  I'll hold off on messing with that pipe until the new fan is in (can pick it up sometime next week, and put it in around Christmas).  The new fan had the same measurements and style so I'll be surprised if it doesn't fit up nicely, but nothing is irreversible yet!

We're picking up spray foam today so I'll check out their pipe insulation while we're there.  I did a quick search on CL for pipe insulation but need to nip up there and measure the pipe size before purchasing anything.

Thanks again!