insulating crawlspace in basement.

[Jeffrey Ellin]

Hi, I Just moved into a new three level townhouse. All Three levels are above ground. The front entrance is between the 1st and 2nd levels. Stairs go up to the living room and stairs go down to a hallway which leads to the garage door and basement area. Under the stairs leading up there is a closet which leads to a crawlspace under the foyer. The floor is concrete, there are two finished walls, one abuts my neighbor the other the garage. The wall with my neighbor is insulated, the wall with the garage is drywalled so I don't know what is in there. The third wall is concrete which is exposed on the outside as well. This closet is freezing, which makes the hallway and foyer cold. The floor in the foyer is fairly cold as well. I am thinking I definetly should insulate the ceiling, how about the concrete wall? Will foam board insulation be effective? Do I really need to install drywall over it? The wall is only 3ft wide and there are no mechanicals in the room.

Here is a diagram of the lower level in case it helps. My scale is way off.

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv f g f Garage g f g fggggggggggggggddddg f c closet w w f r w w f a w w f w wwwddww d f l w d f ssssw w fnnnnnnnnvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

n = unfinished shared wall insulated. v = finished shared wall with neighbor, insulation unknown f = front wall poured concrete, exposed on outside. g = garage wall finished insulation unknown w = finished interior wall, insulation unknown d = door s = stairs to foyer

[George E. Cawthon]

Apparently this crawlspace is totally enclosed. Definitely line the concrete wall with 2" foam as the easiest option, and extend the foam a foot toward the center of the room. Make sure that the dirt of this crawlspace is covered with a thick plastic layer and that it extends up past the footing. If it doesn't, add a 6 mil plastic that does and will extend at least 3 feet out from the wall. I don't think you need dry wall over the foam, at least here you don't. If the code there say it is needed, I would forget the foam and use 3-1/2" thick by 24" wide fiberglass batts and make the batt long enough to extend from the floor above down the wall and 18' out into the room. You need to make this space, the closet part of the house with heat to it. You don't need to insulate the ceiling even if this space remains cool.

[Jeffrey Ellin]

two walls are finished, would the foam still be necessary extended into the room?

There is a concrete floor.

If I were to install bats would I need to build framing into the wall to support them?

I don't quite understand this sentence.

[George E. Cawthon]

Sorry. Mind went wandering with the word crawl space.

No, just hang with staples at the top. Now that I realize this isn't really a crawl space, I suggest it depends on what you intend to put in this room for and how big it is. If you go with foamm use 2" stuff and then cover it with drywall, probably can get by with using construction glue to fix foam board to the concrete and the drywall to the foam board.

What I am saying is that you need air circulation into this space by some means even if it is just putting adjustable grates in the appropriate doors.

[Jeffrey Ellin]

The room is L shaped. The top of the L is a closet where it is finished and has carpet, the carpet stops at the bottom of the L and there is just concrete floor. The area that is unfished is about 3' x

6' far 6' wall is the one that is concrete and uninsulated. The ceiling in the uninsulated space is about 3' high. Since the two side walls are finished I would guess that I really only need to insulate the concrete wall wich has a total area of about 18 square feet. Would you still recommend foam with drywall, foam only or bats?

[George E. Cawthon]

Ok, now I understand the space. I suggested the foam as I thought you would likely end up leaning stuff against the insulation. So here is what I suggest: Bats for the 6 x 3 foot wall. Bats for the floor of this space and if you plan to store stuff in this space put down put 2x4s (the thick way vertical) with the batts between them and then set stuff son the 2x4s so that the batts aren't compressed. This would allow circulating air to warm this area sufficent that nothing would freeze. Actual temperatures would probably be a minimum of 50 degrees and if not a 100 W light bulb would keep it at 50, so the floor above would not feel cool.

[Jeffrey Ellin]

Any particular type of insulation you reccomend?

[George E. Cawthon]

Nope, brand doesn't much matter, just fiberglass bats with a barrier, aluminum barrier, if that turns you on, otherwise just a paper barrier. I'd use 24" wide stuff 6 inch thick.