Basement Insulation

[Defence21]

I'm considering a partial remodel of our basement that currently is already partially remodeled. Part of the basement once was a rec. room with paneled walls and a carpeted floor, but it looks as though there was some water damage that resulted in the removal of the carpet and some of the paneling. Since then, I've been informed that since then measures were taken to prevent a similar problem in the future, and in our three years here, we've experienced no water or moisture issues in the basement. So, since we're confident water issues don't exist, my wife and I would like to take what exists and improve it minimally so we can create a living space to store our daughter's toys and for me to watch hockey with some of my buddies.

So, with the back story out of the way, here's the question. The paneling on the wall is supported by furring strips that keep it roughly 1 inch off the wall. I would like to pull off the existing paneling, insulate behind it, and put the paneling back up. I've considered pulling everything down, reframing the walls with 2x4s and drywalling it, but it's not a space we expect to use on a regular basis and don't want to invest a ton into it. So, with that being said, would an R-6.5 1/2 inch polyisocyanurate board be enough to properly insulate the basement? I don't need it to be overly insulated, as it's not extremely cold down there as it is (we have a cast iron radiator at one end, cats iron pipes that throw off a lot of heat running the length of the room on the ceiling, and an electric space heater permanently mounted on the wall at the other end.

[Willie Kool]

A few problems with that plan. Polyiso board is R6.5 at 1 inch thickness, at 1/2" you're only at R3.3. More importantly, code requires a minimum of 1/2 inch of drywall or equivalent flame barrier over any foam insulation. Panelling will offer no protection in case of fire, and burning foam is extremely nasty. I would frame it out with 2x4's, install 3" iso board sealed around the edges with canned foam (Great Stuff) and finish with 1/2" or 3/4" drywall. That gives you ~R20, meets code, and allows easy wall wiring for the room.

[mac5155]

Was just going to say, need some drywall on insulation. WK beat me to it

[ajh2298]

Not to hi-jack the thread but I also have a question dealing with basement insulation. I have a unfinished basement that get rather chilly in the winter. We also have hardwood floors on the first floor above the basement that seem rather cold when you walk on them with bare feet. My question is can I somehow insulate the celling in the basement to try and make some sort of barrier to keep the first floor floors a little warmer?

[Alejandro Rojas]

Spoiler:

[Willie Kool]

Not to hi-jack the thread but I also have a question dealing with basement insulation. I have a unfinished basement that get rather chilly in the winter. We also have hardwood floors on the first floor above the basement that seem rather cold when you walk on them with bare feet. My question is can I somehow insulate the celling in the basement to try and make some sort of barrier to keep the first floor floors a little warmer?

I don't think insulating the floor joists would help much. You'd have to either get some supplemental heat in the basement or install some type of underfloor radiant heating to see much difference. Of course, a few good wool area rugs can make that hardwood pretty cozy.

[mac5155]

Insulation is good for keeping warm in, not as good at keeping cold out. I'd try and heat the basement somehow

[Defence21]

Somehow I forgot that I posed this question early last month and never came back for the response...which is weird, considering I visit NPR multiple times daily and generally stay aware of threads I create.

Anyway, thanks to those who responded, specifically Willie Kool.

Followup question: In Western, PA -- specifically Johnstown -- if I was to insulate with fiberglass, would my moisture/vapor barrier go against the concrete foundation with the insulation between the barrier and the drywall, or would the insulation go against the concrete foundation with the barrier between the drywall and the insulation? Also, if the barrier is between drywall and insulation, should it go on the outside or inside of the 2x4 framing?

I've determined at this point that I am going to frame it all out with 2x4s before insulating. I've been told poly is the best (as you indicated), but my basement is far from cold and seems to retain heat in the winter. Several co-workers and friends have suggested just using fiberglass at an R-13 value, which should keep things warm enough. One person, however, told me fiberglass is a big no-no in a basement, despite the fact that I've seen it in professionally finished and unfinished basements.

Thoughts?

[Willie Kool]

Actually, I'd agree with that one person. I really don't like fibreglass in basement walls. The main problem with insulating basements is moisture intrusion, from both the interior and exterior. Water leaking or wicking through the concrete from outside is only part of the problem. Any air infiltration into the wall from inside will lead to condensation within the wall when the warm room air contacts the cold concrete behind the insulation. Fibreglass is far too permeable (to both air movement and water vapour) to prevent the moisture related issues (mold) that will almost certainly develop.

IMO, the ideal retrofit is to spray 1" closed cell over the whole wall (or cover the wall completely with 1" isoboard). Frame with steel studs, install electric and plumbing, and spray to fill the cavity with closed cell (or fill in with iso and seal with canned foam). Finish with 3/4" drywall.

That said, if you go with fibreglass, I think any vapour barrier (if used) should be on the concrete. The below grade exterior portion of the wall, in contact with the soil, should be considered to be at ~100% humidity. Any moisture in the wall will have to dry to the interior. If you use wood to frame, I'd use a pressure treated bottom plate over a poly sill sealer to prevent any wicking up through the studs.

[Defence21]

Willie, in searching Lowe's and Home Depot's web sites, neither offers 1" isoboard near me -- 1/2" is available, though. I highyl doubt I can afford to have the basement sprayed, so what do you suggest at this point?

You don't live near Johnstown, do you?

[Willie Kool]

I'm not a contractor or any kind of insulation expert, just a homeowner that has researched this in the past. To doublecheck myself and not give you bad advice, I decided to look again this morning and found this link from This Old House. This may be a better way to do it, using 2" tongue & groove polystyrene panels and furring strips.

http://www.thisoldhouse.com/toh/video/0,,20332381,00.html

I also saw a suggestion to frame out a full wall in front of 1" polystyrene foam and fill it with borate-treated cellulose (Nu-Wool) to up the R-value. If the foam barrier is continuous (I'd probably still tape the seams even if it's t&g), this seems to be a good and safe idea. No idea on the cost though.

http://www.homeconstructionimprovement.com/insulating-basement-with-cellulose/

[shmenguin]

http://markgroupusa.com/

this company is going to take care of all my basement/attic/garage/etc insulation. in NJ (at least), the state subsidizes this sort of thing, so right off the bat, i'm saving something like 25%. it's also no interest financing for a 10 year term. and you can throw in a new furnace and water heater with this discount and with this financing.

[yubb]

Is any of your basement below ground? I've been told that if it is then you don't need to insulate.

[Defence21]

@Willie, I'm intregued by the TOH method of PolyIso glued to the wall, then 1x3s to create a grid to screw the drywall to. It seems like it would save money on the framing costs as opposed to using 2x4s, and it also would prevent the loss of space (albeit minimal) in my basement, which already is small. I'm thinking this might be the route I take.

@shmenguin, I'm not looking to finance and really want to go bare minimum in costs, while doing it right.

@yubb, it is 3/4 underground, but I still want to insulate to help keep the heat in for when my daughter plays down there during the winter months.