# Basement Insulation and Vapor Barrier Questions



## Dane78 (Dec 21, 2020)

I am in the process of remodeling a portion of my basement. Older home built in the 60's- block basement walls. I pulled the paneling down and the exterior block walls have a plastic vapor barrier directly on them. The studs are attached to the block on top of the plastic. 
I am going to install drywall. Should I put some sort of insulation between the studs? The studs are only 1.75 inches deep.
Was thinking some sort of unfaced insulation so any moisture can move between the insulation and drywall. We have not had any water issued in the basement. Walls are about 7 feet tall and almost the entire wall is below grade. 
Any advice is much appreciated.


----------



## Bud9051 (Nov 11, 2015)

Hi Dane and welcome to the forum.
If starting from scratch that probably isn't the way I would recommend doing it. But we don't know your climate region or long history on the basement?
Liquid water is what you would see and you indicate none. But moisture vapor is the sneaky form of a moisture concern and being all below grade and a block foundation I'm reasonably certain you have moisture vapor coming through.. Not sure you would want to tear it all out and start over so here are some comments. Fiberglass insulation would provide little insulation value that thin. Maybe custom fit rigid foam board. Air sealing at all points to prevent basement air drom reaching the cold walls is vary important.

Best
Bud


----------



## Nealtw (Jun 22, 2017)

I agree, don't fix what is not broke.
Foam board would be good but a good fit leaving no voids so you have no air behind the wall would be the way i would go.


----------



## Dane78 (Dec 21, 2020)

Bud, Thanks for chiming in. I don't want to tear it all down and start from scratch. It has likely been in place for 40 plus years and seems to have held up well. Few areas where the plastic has been damaged by mice and bugs. I'm in the DC/Baltimore area. 
Do you think I should put the rigid foam board over the existing plastic? How would you go about attaching it without damaging or compromising the plastic?


----------



## Dane78 (Dec 21, 2020)

Should i use faced foam board? Seal the gaps with foam, like great stuff? Or caulk?


----------



## Bud9051 (Nov 11, 2015)

Looks like the plastic is behind the studs so a little glue maybe and sandwich the rigid in place. 1.75" sounds like they ripped some 2x4 material in half so some fudging to get the fill you need. Now if codes come into play that may not be sufficient but I'm not saying anything.

At the top of the foundation where the house rests on the blocks it is often a location where air leaks in. Caulking or can foam are often used. I like the big tubes of PL300 and I can get my fingers in there to make sure it is where I want. You can't touch can foam until it is dry. Once sealed then the rim can be detailed with more pieces of right.

Bud


----------



## Dane78 (Dec 21, 2020)

Thanks again for responding. I can't locate much information about my scenario. I'm going to install the foam board.

I just need to determine if I should use faced or unfaced board? Any recommendations or thoughts on this?


----------



## Bud9051 (Nov 11, 2015)

The foil or plastic faced foam board becomes a true vapor barrier with that facing. Blue or pink rigid foam board (no facing) is actually a vapor retarder allowing a very small amount of drying to the inside, easily handled with the heating or cooling system. The benefit being it reduces the chance of accumulation.

Bud


----------



## Dane78 (Dec 21, 2020)

Happy Holidays everyone.
Any issue with a gap between the foam and drywall? Will 1 inch foam board be okay in this scenario? Or do I need foam or insulation against the drywall?


----------



## Porsche986S (Dec 10, 2017)

If it were me I would use 1.5 " thick foam board . I would do my best to cut the foam board 1/2 " less than the cavity width , this leaves aprox. 1/4 " gap on either side . I would set the foam in place and toe nail three or four nails on each side holding the foam board in place . When you are done installing all the foam board get enough spray can foam to do the perimeter in each cavity . This will provide decent insulation value and seal at the same time . The 1/4 " gap between the foam face and the sheetrock adds a tiny bit of insulation value and allows it to breathe a little .


----------

