Opinion on adding foam board insulation on the interior over existing drywall.

FrankSmith · Jan 13, 2015

I would go in the attic and block of the top of every interior and exterior wall. I would block it off with wood and then foam any air gaps. I would go to the basement and block of and foam any gaps down there. If you can get the walls to stop connecting to the attic it will instantly feel warmer. This of course is only a start but it is a rental.

hdavis · Jan 13, 2015

FrankSmith said:
I would go in the attic and block of the top of every interior and exterior wall. I would block it off with wood

I use foamboard - I can cut and fit right in place.

TNTRenovate · Jan 13, 2015

hdavis said:
I use foamboard - I can cut and fit right in place.

I also fireblock spray foam all penetrations and drywall to top plate seams.

TNTRenovate · Jan 13, 2015

To the OP, why not spray foam injection?

FrankSmith · Jan 13, 2015

So long as it stops air and fire it sounds like a good plan to me. I have seen people stuff fiberglass in to try to block the cavity off and its stops neither air or fire. I think that blocking this off is the biggest bang for the buck to get started.

Lugnut1968 · Jan 13, 2015

Gotta go with TNT on this one... spray foam injection all the way. To me this whole deal is about like asking if you want to be shot or stabbed... imho spray foam injection is being stabbed the least to me.

illbuildit.dd · Jan 13, 2015

these houses are never nice to us. gutting is obviously the best option. bandaids and quick fixes lead to high energy bills/unhappy renters. one of my clients usually consults me before buying houses, but two houses back he didnt. he asked me to bandaid it up, and the can of worms kept growing. which is a common occurrence. so in the meantime.... foam injection is what i would do as well.

unless someday the house would need re-wiring??

SLSTech · Jan 14, 2015

The problem with injection foam is will it last - highly unlikely as I still hear cases of pulling away, etc... The next is if you haven't solved your flashing errors you are going to run into water & rot issues.

As for "if wiring needs replaced" - if that is a concern, you shouldn't be installing it in the first place especially if it is K&T or aluminum. I would say the older style romex type but as most houses here use conduit that isn't as big of a concern.

As it is a rental - air seal & fire block are going to be your biggest savers with least risk. Next look at the attic for insulation - but if there is any K&T don't insulate unless you rewire first --- Airsealing & insulation articles

CaptainRon · Jan 15, 2015

SLSTech said:
The problem with injection foam is will it last - highly unlikely as I still hear cases of pulling away, etc... The next is if you haven't solved your flashing errors you are going to run into water & rot issues.

As for "if wiring needs replaced" - if that is a concern, you shouldn't be installing it in the first place especially if it is K&T or aluminum. I would say the older style romex type but as most houses here use conduit that isn't as big of a concern.

As it is a rental - air seal & fire block are going to be your biggest savers with least risk. Next look at the attic for insulation - but if there is any K&T don't insulate unless you rewire first --- Airsealing & insulation articles

I agree. And injection foam is a crap shoot as to whether the cavity is evenly and fully filled or not since you can't see it. No K&T thank god. Was rewired at some point. And what an easy rewiring job that was with unobstructed walls. Will do as suggested and just seal off leaks for now and add more insulation in the attic. This will be the first month that I've really had the heat on and it's been well below zero many times, so I'm a little scared to see the heat bill.

91782 · Jan 15, 2015

CaptainRon said:
Greetings all.

I'm doing a small remodel on a 100 year old home to use as rental property. There is zero insulation in the walls. The walls have the original lath and plaster with 1/2" drywall over that. I really don't want to tear all that out and open the walls. I'm not a big fan of blowing in insulation from the outside. For one, it's too expensive for this project and I know there can be issues with putting insulation in the walls of old houses because there's no vapor barrier behind the plaster. I know there are many opinions on the subject. I've opened the walls of old houses before to find the insulation wet and moldy due to the lack of a moisture barrier on the inside. I thought perhaps I could install 1" foil faced foam board over the existing walls, fur it out and install 3/8" drywall over that. I know the R-value would be minimal, but it's better than zero R-value and should help at least some to slow down the heat transfer. My concern is, will this also create a moisture problem. Will moisture be trapped between the foam board and the new sheetrock? Any and all opinions would be appreciated. Thanks.

Back to the original question: Doing foam OVER plaster would be no better/worse than any other method when it comes to moisture, IMO - depending on how sound the plaster is.

I have never seen it done tho.

Man, that's got to be a LOT of work too - especially if you give a damn what the casing/mop boards look like afterwards.
:no::no:

Donohue Const · Jan 15, 2015

I would say no on the injection foam
One guy who works for me now used to do that retro foam for a big foam company
He said it it's not worth it, it doesn't last

Do nothing, or gut it and do it right.

Opinion on adding foam board insulation on the interior over existing drywall.

FrankSmith

hdavis

TNTRenovate

TNTRenovate

FrankSmith

Lugnut1968

illbuildit.dd

SLSTech

CaptainRon

91782

Donohue Const

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