Insulating Existing Walls

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bbauman1
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Insulating Existing Walls

Post by bbauman1 » Wed Oct 30, 2019 10:29 am

I have an older home that has a boiler system with baseboard heat. This winter we are planning on removing the plaster walls to install ductwork for a new furnace and A/C. The walls do not have insulation in them and the house only has cedar siding with no vapor barrier. I was told that I do not want to add fiberglass insulation because of the moisture and humidity that would penetrate through the walls, which could cause mold. I talked to a foam installer and he said that the best thing to do would be to spray closed cell insulation. However, I have also heard negative reviews about that type of insulation. I was just wondering if anyone had any other opinions or information on the best approach. Thank you!

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Shannon
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Re: Insulating Existing Walls

Post by Shannon » Wed Oct 30, 2019 3:51 pm

Well in my area I would say 85% of homes are batt insulation and we have air/vapour barriers on the inside under the drywall . If you are stripping the interior walls you will be able to install an air/vapour barrier and should unless you are in a climate that does not require them?
I would guess that the moisture /mould topic was brought forward by the foam installer? He wants to sell you on his product.
Don't get me wrong when closed cell foam is done and done right it is a great product,.... costly but great solution for insulation and sealing a home.
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bbauman1
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Re: Insulating Existing Walls

Post by bbauman1 » Thu Oct 31, 2019 1:00 pm

He told me that since there is no sheathing behind the siding that moisture and humidity would get into the batt insulation. Which he said would hold the moisture and cause the walls to get moldy over time. It makes sense, but perhaps it was just to sell me on the closed cell foam. I have heard that I should put foam board with a 3/4 -1 in gap from siding to allow an air gap. Therefore, the siding would be able to dry completely from the inside also. The foam installer suggested that closed cell would seal the siding from any moisture which wouldn't require an air gap? From what I have gathered for my situation, is that even if I do the closed cell insulation I would still want the air gap.

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Shannon
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Re: Insulating Existing Walls

Post by Shannon » Thu Oct 31, 2019 5:25 pm

ok so you said no "vapour barrier " but in reality you meant no house wrap on the exterior. Ok the sprayfoam makes more sense now. The sprayfoam would be the better way to go then in this case. If you do open cell then you may need to install a poly air/vapour barrier on the inside before re drywalling.That you will have to check with your local building codes.
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Wilxman
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Re: Insulating Existing Walls

Post by Wilxman » Thu Oct 31, 2019 8:49 pm

Whatever insulation you install between studs, if you hang a poly vapour barrier over the interior wall and then attach gypsum sheetrock, won't you compromise the vapour barrier with the drywall nails? Using dozens of staples to secure the poly to the interior face of the studs....will that not compromise the vapour barrier? Do codes describe the best way to install vapour barriers? And with closed cell spry foam, is the poly barrier really needed or maybe doesn't matter?

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Shannon
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Re: Insulating Existing Walls

Post by Shannon » Fri Nov 01, 2019 8:16 am

You bring up valid points . Yes you do puncture the barrier but there is very little leakage where drywall sandwiches the barrier against a stud and this is a very accepted procedure . You could run a bead of acoustical caulking on each stud under the barrier which would then seal around any punctures. Alternatively using a min. of 2" of closed cell spray foam does not require an additional air/vapour barrier. Check your local codes to verify before proceeding.
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bbauman1
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Re: Insulating Existing Walls

Post by bbauman1 » Sat Nov 02, 2019 6:24 am

I talked to another insulation company and they do blown in wood fiber insulation. Is that a good solution? He told me that it would work for my situation because it wicks the moisture towards the outside.

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Shannon
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Re: Insulating Existing Walls

Post by Shannon » Sat Nov 02, 2019 10:44 am

bbauman1 wrote:
Thu Oct 31, 2019 1:00 pm
He told me that since there is no sheathing behind the siding that moisture and humidity would get into the batt insulation. Which he said would hold the moisture and cause the walls to get moldy over time. It makes sense, but perhaps it was just to sell me on the closed cell foam. I have heard that I should put foam board with a 3/4 -1 in gap from siding to allow an air gap. Therefore, the siding would be able to dry completely from the inside also. The foam installer suggested that closed cell would seal the siding from any moisture which wouldn't require an air gap? From what I have gathered for my situation, is that even if I do the closed cell insulation I would still want the air gap.
If you are using foam board then the air gap is a good idea but i think with all the messing around you might as well do closed cell and be done with it. You get a air tight wall and good R value and it should repel any minor moisture.
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