To Insulate or not to insulate

[Larry Fox]

I live in SE PA and am finishing my basement to add living space to my house. The floor joists above the ceiling are uninsulated and the walls I am building will be close, but not touching, the block walls. It is a little on the cool side down there in the winter but not unbearable. I was not going to insulate because I didn't think you were supposed to insulate interior walls. However, the other day I was talking to someone and they strongly suggested that I insulate. Anyone with experience with finishing/finished basements have any insight on this?

Thanks in advance for your time . . .

L

[Tad Capar]

Larry,
You should definitely insulate, it's the money well spent. Here in NJ is required by code any time you would finish a basement and you're not that far away from here. New houses (well constructed) nowadays have R-10 rigid insulation installed on the outside of the foundation wall where it meets the dirt. Even then you should insulate on the interior.

[Paul Ryan]

Larry,

I would definatly insulate the minimal cost with outway itself. The basement will feel warmer and stay warmer. I suggest using a polystyrene insulation though. It will cost a little more, but many times block walls get most. And overtime that mositure can cause regular batt insultation to begin growing mold. I did my basement I cut 2x2's (used in the place of normal 2x4 studs) nailed them to the walls with the .22 nailer, and put 1 1/2" polystyrene insultation in between the 2x2's. Then put cedar carsiding up. It gave the room a real rustic look and helped warm it up greatly.

[Larry Fox]

I appreciate the replies guys - very helpful. So, couple of follow-up questions.

1) What does one use to insulate a wall that would touch the block wall? If using a regular Bat, does the paper go in our out?

2) Same question about the floor joists above the ceiling? Paper facing up or down?

Thanks again . . .

L

[Chris Damm]

I would not use fiberglass below grade as any moisture degrades it's performance. Closed cell foam (Dow Styrofoam or Owens-Corning pink) is best for this application. What I did was to glue and nail a 2x2 or 2x4 at the top and bottom of the wall, glue foam to the wall, and screw and glue drywall to the wall. I did this in 1981 and it has made all the difference in keeping the space warm and dry. This method as the advantage of not taking up much floor space. For wiring a living space keep the bottom nailer up 1/2" and use this for your wire chase. They make a shallow box that works for this method.

[Lee Schierer]

I insulated the spaces between the top of our block basement wall and the skirt board and floor joists a number of years ago. It made our basement noticeably warmer. Our basement walls have a spray on foam insulation.

[Jim Mattheiss]

Holmes on Homes did a basement a while ago.

They used 2" rigid foam on the walls and 1" rigid foam under the floors. The foam is taped at the joints and foamed at the intersections. I don't recall how they attached the foam to the walls. They tapcon-ed plywood over the foam on the floor.

They build freestanding stud walls OFF the foam and did not insulate them.

I wish I'd done the same on my basement.

I've read where guys glue foam to the block wall.
Then glue sheetrock to the foam. I'm not sure what they do about wall outlets and such.

Cheers

Jim

[Tad Capar]

Spray foam (closed cell) insulation is best for this application, but it is pricey. It's about $1+ per sq ft of 1 inch thick ( 1 inch thick is all you'll need) installed. The next choice would be a rigid insulation which has been recommended here, but it is not cheap, about $1 per sq ft of 2 inch thick (R10) plus your own installation. If this is in your budget then go with spray foam. You can install these " Z-strips" metal furring strips nail to your block wall, rough the electrical and have it sprayed with closed cell foam. (get the quote)
If it is out of your reach, go with the fiberglass, keep it away from touching the block wall. Vapor barrier (paper) goes on the inside.
No need to insulate the area between the joists unless for sound, but do insulate the rim board (area nearest the outside wall around the perimeter) with at least R19. Paper always goes toward the heated side. Hope this helps.

[Doug W Swanson]

When we put an addition on our house a few years ago, we were required to build a stud wall and insulate in addition to the block wall.

What the inspector had us do was to run a vapor barrier next to the block wall, build the stud wall, insulate, and then add another vapor barrier on the inside.

What this does is prevent moisture from getting to the insulation. Any water that gets through the cement block will hit the vapor barrier and fall to the floor.

It sure seems to be warmer than the old, uninsulated basement.

JMO,
Doug

[Mike Cruz]

+1 (or is it +10) for insulating the ceiling...for two reasons: heat exchange AND noise. Without it, you will hear every footstep above you. Also, if you are planning to drywall the ceiling, consider resilliant channeling. It is a long metal piece that is attached across your joists, then the drywall is attached to that. It significantly reduces vibrations and noise transfers from level to level. We put this in the house that my brother and father built (brother lived upstairs, Dad downstairs). You wouln't believe the privacy it gave them. Not ABSOLUTE sound proofing, but certainly TV and conversations were almost unhearable.