vapor barrier basement in Northeast

I am in the process of redoing my basement making it into a livable space. My question is I live in the Northeast, Connecticut, and the basement in below grade. Do I need a vapor barrier between the cement block wall and the sheetrock?

I will be using insulation between the wall and sheet rock, but have gotten different answers about the vapor barrier.

Some have said with a kraft faced insulation I don't need the vapor barrier, because the vapor barrier will trap moisture. Others have said that you always have to use a vapor barrier.

I was just wondering what the pro's here thought and what was the standard practice.

Thanks

Here's another different answer from an amateur who's been there and done that...

If the basement feels damp, you've got moisture. It could be wholly sourced from the inside (i.e., it's normal interior humidity condensing in the cooler cellar), or coming in through the block walls. If it's interior moisture, you need to raise the termperature and/or install a dehumidifier. You can test for incoming moisture by taping a piece of clear plastic on a 3-or-4-foot-wide section of an exterior wall and seeing if moisture collects on the backside. If you've got a severe moisture problem (i.e., lots of moisture collects on and runs down the plastic during the test), you need to get professional help.

If you've just got a small amount of moisture (the aforementioned "professional" would be the best judge), you need a vapor barrier of some kind. It should really be on the outside of the block wall, but I'll assume it's too late for that. You should also have outside foundation drains in place, but it's probably too late for those as well if they aren't there. What's your site layout?

If you've got to do the job from the inside, I wouldn't consider anything other than a sprayed-on polyurethane foam on the block walls. It is its own vapor barrier and an excellent insulator.

I'm sure the real pros on this forum will have better thoughts...

Mikey thanks for the reply, but from what I understand the sprayed-on polyurethane foam does not provide enough R value to keep the basement warm enough.

I am planning on adding heat and a dehumidifer that will drain into the sump pump. Im also adding a sump pump because I occasionally get water. I cant figure out the reason I get water, because a recent storm with several inches of rain, other homes in the neighborhood got water in the basement but mine was bone dry. So i figure the minimum cost of putting in a sump pump would be added piece of mind.

I had called out professional waterproofer companies where they dig up the foundation on the inside of the basement and put in drains, but it was crazy expensive.

Good reading here:


http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems/

ctkeebler,

read the link posted above. also don't use fiberglass a vapor barrier or woood to finish your basement at best those systems are problematic at worst you will have to tear it out and start over.

I would apply xps directly to the basement walls and frame with steel studs which are easier to work with then you think. I don't know who told you that SPF won't have the R value you need its by far and above the best choice for a basement if you have the money its $pendy

Lou

Thanks for the information, I read alot of information and it looks like this may be the way to go. I have torn down sheetrock becasue it had mold behind. The
Mold fiberglass also had some mold and odor.

It looks like my problem may be that the wall is already framed with wood studs and it appears from the Dow site that the foam should be applied before the stud wall is applied or using the wallmate Styrofoamproduct I attach furring strips over the foam to attach the drywall.

The other product, Thermax, it looks like I put fiberglass batts over the foam. I guess I need to do some more research.

I guess the reason why I was told it does not have a high enough r value is it looks like the most is r10 and in the northeast I wsa told r-19 for the basement.

CT,
is having a contractor spray foam with in your budget ? with wood studs already installed thats by far and above the way to go

Lou

Big Lou, I have no idea as I have not priced that option because I thought the fiberglass batts was the proper way. I see that I can use the furing strips with the rigid foam, but Im not sure how if this provides enough nailing for the sheetrock and how to attach the electrical boxes.

Check out this other thread: https://terrylove.com/forums/showthread.php?t=20379

My unprofessional opinion is your best option is professionally-applied sprayed polyurethane foam. It goes on after the furring strips are in place, seals the entire surface, and provides about the best insulation value per inch available (about twice that of batt fiberglass). It's not cheap, as you'll find out if you call around your area for quotes.

You've got 2 options for installing electrical boxes: 1) use shallow boxes and mount them to the surface of the blocks. You will have to be careful with box fill issues. 2) Chisel holes in the inner surface of the block and recess the boxes, fastening them to the furring strips. Squirt some canned expanding foam into the hole to insulate and seal the breach in the foam barrier.

If you use deeper furring strips, you can use more insulation and deeper electrical boxes. I would fur out 2", allowing you to use a 2 1/2" box. Fastening the box to the face of the blocks allows more freedom to place the boxes where you'd like them, independent of the furring strips' locations. Fasten all the cables to the block face, cover the boxes, and spray the insulation.

Can I leave the traditional 2x4 construction walls in place and put the rigid foam behind the 2x4 wall? I have to cut away the bottom plate as it is because its not pressure treated, so I will have some play with the 2x4s studs.

This may leave an air gap between the drywall and the foam insulation depending on the thickness of the foam I can get.

Is there a draw back to leaving a gap between the foam and the drywall?

I was also told that if I use drylock on the walls and them put a plastic vapor barrier against the cement wall I should be able to use batt insulation without an issue? But this advice seems to be against the advice I get here.

When I did mine, I glued 1.5" foam to the foundation wall and built 2x4 wall in front of that. In some walls, I also added unfaced unsulation in the 2x4 wall. A gap between the foam and 2x4 wall is fine. The key is drying and avoiding trapping moisture.

Charlie, that is what I was thinking or just using 2 inch foam leaving the air space between the drywall and the foam. I guess the 2x4 really gives me about 3 1/2 inches so I would have to see how thick or thin the batt insulation is so its not jammed between the foam and the drywall.

Hi all...just found this thread while doing a search on vapor barriers...and trying to find 2 similar answers is driving me crazy!

I'm finishing my basement (in the Pittsburgh, PA area) and have done something similar to what CharlieM did...glued foamboard to the cinderblock, built 2x4 stud walls starting 1/2 inch from the foamboard, and just now finished adding 3 1/2" kraft-faced fiberglass in the stud walls. Now, here's my question...am I in good shape to drywall now or should I tear off some of the kraft-facing on each fiberglass batt to allow for more air flow? I checked out the Building Science website and could not find a definite recommendation as to use faced or unfaced batts. I thoughy using unfaced would be best to allow for more air flow, but I couldn't find them batts at the local Home Depot or Lowes...they only had the kraft-faced.

Any help/advice is appreciated! Thanks!

MLB

PS - Instead of tearing off some of it, would just cutting a few slits in the facing suffice?

MLB, I would just cut slits in the kraft paper.

I used 2x4 walls and no vapor barrier and unfaced insulation. No vapor barrier will let the wall breath. Any kraft facing, spray foam or foamboard has the potential of trapping moisture. I put a 4" heat run in each room and they are the warmest rooms in the house.

Thanks for the replies! The basement is pretty dry...we have a radon system installed that helps...and I will install 2 baseboard heating units, too.

MLB