Insulating Stairwell Into 2nd Floor

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DIMwhit
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Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Sun Sep 22, 2019 11:22 am

I have an unfinished 2nd floor with an actual stairwell, not an attic hatch. I would like some advice on how to properly air seal/insulate. Currently the inside of the stairwell gets very hot in the day. It’s got drywall on the inside of the stairwell and its framing has batt insulation with the paper toward the interior drywall. No drywall on the outside/framed side of the stairwell.

Here’s a picture from the 2nd floor. I’m very worried about the air leakage coming from this area.

Thank you for your time.
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DIMwhit
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Re: Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Sun Sep 22, 2019 11:31 am

...also it has an interior door at the top of the stairs with a sizeable gap at the threshold. I have towels and foam shoved in the gap but I don’t think that’s the problem.

P.S. attic roof decking is not insulated (yet).

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Shannon
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Re: Insulating Stairwell Into 2nd Floor

Post by Shannon » Mon Sep 23, 2019 7:08 am

What is your plan with this space? will the second floor be a usable conditioned house space? If so then after it is all insulated you would then add air vapour barrier and drywall. If its not going to be finished and conditioned then the stairwell needs to have air vapour barrier under the drywall that is on the inside. Don't forget about the ceiling of the stairwell as well. The door itself is likely letting a lot of heat/cold through it so either installing an insulated /sealed door or adding foam and weather strip to the existing door would help.
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DIMwhit
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Re: Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Mon Sep 23, 2019 10:50 am

Shannon,

Man you are awesome! Thank you for getting back to me. 👍

My plan is to finish the entire second floor with a little electrical help from a friend. Great thought about the area above the stairwell—I had the same thought. I bet it’s hottest there and I haven’t been all the way up there to see it yet. Yes, it will be a conditioned space. I’m thinking about spray foaming the roof decking or putting the rigid foam but not 100% which direction i’ll be going yet. So over the top of the current batts I would install air/vapor barrier? Kinda like your basement video?

Would I need to cut a rabbet in the jamb if there is none (for weather stripping)?

Thanks Shannon!

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Shannon
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Re: Insulating Stairwell Into 2nd Floor

Post by Shannon » Tue Sep 24, 2019 5:50 pm

Well if you are finishing the entire area then insulating the the stairwell is not needed.
You will insulate the exterior walls and ceiling and depending on your local codes you may or may not need a vapour barrier. Also weather stripping the door should not be needed.
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DIMwhit
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Re: Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Wed Sep 25, 2019 12:41 pm

Initially I can’t afford to finish the entire area. Do you think I should continue with finishing the stairwell & then do the rest as my funds build up?

Thanks.

Btw the stairwell ceiling is not insulated. Got up there just now.
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Shannon
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Re: Insulating Stairwell Into 2nd Floor

Post by Shannon » Thu Sep 26, 2019 8:23 am

Insulate the top of stairwell and don't worry about poly if your plans are to insulate the actual second floor over time. This should keep the stairwell cooler.
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DIMwhit
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Re: Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Wed Oct 02, 2019 5:08 pm

Would you closed cell spray foam the roof decking, use roxul, batt, or blown-in ideally? I’ve been watching vids on the spray foam and looking into the Dow Froth Pak and some other options.

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Shannon
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Re: Insulating Stairwell Into 2nd Floor

Post by Shannon » Thu Oct 03, 2019 7:33 am

Well personally I would use spray foam on the roof decking in the areas that also serve as the "sloped" walls of your attic right down to the top plate of your walls below the floor. The flat ceiling I would use either blow in or a combination or blow in and batts.
Just to clarify an earlier point , don't worry about vapour barrier on the walls of the stairwell since you are planning on finishing the attic area soon. But you will need it on the ceiling of the stairwell and eventually the entire ceiling . For above the stairwell I would cut strips about 4" wider than the joist spaces that you can fit and seal to each joist before insulating. Install 2x4 blocking between the joists spaces laying flat and flush to the bottom of the joists at the perimeter of the stair well. This will give you an spot to seal the poly and start and stop when you add the next poly to the entire ceiling later.
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DIMwhit
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Re: Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Fri Oct 04, 2019 10:07 am

I had to put some pictures for context. So you would put spray on all sloping walls down to the top plates of the 1st floor walls? Do I need to pull up all existing subfloor on floor 2 or could I cut certain parts away? The ceilings of floor 1 already seem to have cellulose blown in.

Thank you.
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Re: Insulating Stairwell Into 2nd Floor

Post by Shannon » Fri Oct 04, 2019 11:28 am

So what you have is a lot going on with that type of structure and you will have to kinda do a "hybrid" type insulating to get it working properly.
Your sloped walls/roof are only 2x6 and there is lots of solid blocking in the spaces. To insulate a roof like that with batt insulation you need a 1' air space between the roof sheeting and batts for air circulation from the eaves to the ridge. 2x6 does not give you enough space to do that and still keep a decent R value that is useful. Also all the blocking creates other problems fro proper circulation. So I would recommend 2"-3" of closed cell spray foam in all those areas, and the natural places to start and stop the foam are right from top of top plates of 1st floor walls right up to a point about 2" above the bottom of the flat ceiling joists. From what I see in the pictures you likely do not need to pull up any floor but you will need more blocking along top plates and stopping point at the top. These blocking areas will give a surface to spray against to get the seal you will need. Spray foam contractors can show and explain exactly what they need you to do for that. I personally would hire this out instead of buying DIY sprayfoam kits for this amount of area.

The insulation in the floor is fine, it won't hurt anything.
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DIMwhit
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Re: Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Sun Oct 06, 2019 9:08 am

How do I trust a contractor who may be less educated on their product than even I may be?!

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Shannon
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Re: Insulating Stairwell Into 2nd Floor

Post by Shannon » Sun Oct 06, 2019 10:42 pm

Im sorry but there are good contractors but you are correct there are many who are not . IMO have 3 or so come look at the job tell them what you wanna do and see what they say and what they will charge. I have basically explained what they should do so you do have some understanding on what they should be suggesting.You want closed cell foam.
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DIMwhit
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Re: Insulating Stairwell Into 2nd Floor

Post by DIMwhit » Mon Oct 07, 2019 9:50 am

Thank you Shannon, you are a gem! I appreciate everything.

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