Wall Insulation

[Jeff396]

I am in the process of finishing a basement. I have always been confused as to what type of insulation to buy ie when to get a vapor barrier and when not to. I have three situations....1. interior studwall between the garage and basement, 2. Exterior studwall and 3. Exterior cinderblock wall with 2x4 studwall fur out. Question is, would I want to use insulation with the paper vapor barrier in all of these locations? Where would you use insulation without the paper backing. I am planning on painting all cinderblock walls with a waterproofing paint before insulating and am unsure if this makes any difference. Any help would be appreciated/w3tcompact/icons/smile.gif.

Jeff

 

[StoneHeartFarm]

Jeff

You could use the non-backed insulation in a well vented attic as an additional layer over top of existing insulation. Or, in a wall where you are planning to use a plastic vapor barrier. The idea is to prevent a double vapor barrier. In other words, a paper barrier with a plastic barrier over top. This causes moisture to build up between the plastic and paper barriers, and eventually seek a way out that may not be to your liking.

SHF

 

[cowboydoc]

Personally I have just used the paper barrier insulation and that was it. Never had any problems that I know of. We'll be building again in the spring and that's what I plan on doing there as well.

 

[Rodneyd]

Jeff,
You should always use a vapor barrier when there is a temperature difference between one side and the other. In your case, if the garage is cold and the basement is heated, then the barrier should be on the basement side. The only time you wouldn't use a vapor barrier is if you are adding insulation on top of existing insulation in an attic or between walls in your house for sound proofing like between bathrooms and living areas. In the area where you have the block walls I would tend to put in the styrofoam sheets between the studs and then put plastic for the vapor barrier on the studs toward the room. The reason for styrofoam is that it will not absorb moisture. Fiberglass insulation will tend to absorb moisture at times and then remain damp and rot out the studs.

Rod

 

[DFB]

Jeff, have you seen what the The Home Depot advertises?

They have a basement wall insulation system consisting of extruded 1 1/2" x 2' x 8' polystyrene (rigid pink) panels R7 value with notched edges when butted together leaves a space to to anchor them to the wall with a 3/4" furring strip. No other vapor barrier required.

If you haven't already framed a stud wall or don't need the depth for for recessed electrical work it looks like a fast and easy way to do the basement walls. I'm planning on using it to finish off the concrete basement walls on the new house when its done, and use kraft paper backed insulation for the interior partion and exterior 2X studded knee walls.

DFB

 

[Jeff396]

I am going to have to put in recessed electrical. We already have the interior stud walls for a bedroom, mainroom and a bathroom in place including rough plumbing in the slab courtesy of the builder. Too bad, that sounds much easier than what I have planned.

Last question your responses brings up. Would I be making a mistake by painting the cinderblock walls with that water sealing paint before I put the stud walls up. I was wondering if this would constitute a double vapor barrier when combined with the paper insulation vapor barrier or plastic over foam on the inside of the studs. It sounded like a good precaution but now I am wondering if it would trap moisture in the walls.

Jeff

 

[RobS]

OK, I probably went overboard here but it didn't cost much in either time or money...

I put a vapor barrier on BOTH side when I finished our basement. Before I put up the studs I used some construction adhesive to put a sheet of poly on the poured concrete wall, but only up as high as the grade on the outside. Then I put the stud walls up with the bottom plate on the poly and wrapped it up the inside of the stud wall. I insulated then put a sheet of poly on the inside and rocked it.

Not sure if it's right or wrong, I just didn't like the thought of moisture getting into the insulation from either direction in a basement /w3tcompact/icons/smile.gif

 

[beenthere]

You may be okay, but you have set up the perfect conditions to trap moisture, unless you provided vent holes to vent the area between the two vapor barriers. Venting the cold side of the insulation is needed.
Keep an eye out for carpenter ants, as they are the best indicator of high moisture problems in wood. Carpenter ants won't eat dry wood, but they like damp, wet wood. Time will tell if you are going to have a problem.

 

[DFB]

Jeff, I don't think sealing the block with a waterproofing paint should cause any problems.
My first thoughts were that it should help insure exterior moisture won't get thru the walls to ruin your work. Have you already waterproofed the outside of the foundation in some way?

I did do a little web searching too and came up with this Q & A page for finishing off a basement.

<A target="_blank" HREF=http://www.handymanwire.com/questions/basementfinishingq.html>www.handymanwire.com</A>

DFB

 

[ronjhall]

Jeff
I was listening to the other day. You may have listened to him on 1270 WXYT radio when you lived in Detroit area. He recommended a Dow Corning site that gives recommendation on how to install all types of insulation. Check this <A target="_blank" HREF=http://www.owenscorning.com/around/insulation/fallpromo/4.asp>LINK out.