Replies

1. 
   ssnellings | Mar 05, 2021 10:36am | #1

   If you don't insulate those interior concrete walls there will be heat loss. However, you're already not insulating behind the stairs, so compromises have already been made. Not insulating the interior walls is just another level to that compromise.

   Check with your inspector on the clear height issue. If the lower area is in an egress path you are more likely to get dinged for it, but in the end your inspector has the only opinion that matters.

1. 
   josh_in_mn | Mar 05, 2021 12:02pm | #2

   For low clearance areas like by your stairs have you considered a product like Insofast? It's an EPS foam with embedded plastic nailing strips, so you can apply it to the wall, add 1/2" drywall for protection from damage and fire, and be done. It's expensive, but great for stuff like this.
   https://www.insofast.com/

1. 
   PLIERS | Mar 05, 2021 12:14pm | #3

   That’s a good product but I’m not running any wires along the wall. Is it basically just the run of stairs. When I hit bottom of stairs I got about 3 feet to wall. I could add 1 inch insulation and attach 1/2 inch drywall directly to concrete. That would give me some insulation without making wall too thick.

   I would loose some heat in interior concrete walls without insulation but don’t know how that compares to the concrete walls that are on outside. If it’s minimal I’m willing the compromise

2. 
   artisanfarms | Mar 06, 2021 10:56am | #4

   I wouldn't insulate the interior walls unless you are planning on installing doors between the rooms and keeping each room at a significantly different temperature. This doesn't seem any different than not insulating interior rooms on the main floor of the house. The temperature is the same on both sides of the wall so you're not trying to minimize heat transfer.

1. 
   charlie_sullivan | Mar 06, 2021 01:47pm | #5

   The difference is that the concrete walls are attached to the uninsulated (?) slab, and are a good enough heat conductor that the cold from the slab conducts up into the wall.

1. Expert Member
   BILL WICHERS | Mar 06, 2021 02:33pm | #6

   It's a minimal issue from the slab. The slab is, in effect, the warmest part of the basement exterior since it's the deepest underground. You'll see the most overall heat loss from the exterior walls, and the most heat loss on those walls from the portion above the frost line (and even worse, any portion that is above grade).

   The areas where thermal bridging will be worst is where those interior walls connect to the exterior foundation wall. The issue will be worse the closer you are to the exterior wall, and will diminish as the wall goes further inside. If you had a way to insulate the first foor or two you'd get most of the benefit, but you'd have a bump-out that would look wierd.

   You'll get the vast majority of the benefit of an insulated basement here by just insulating all of the exterior walls. Not insulating the interior walls loses you very little, and I probably wouldn't bother insulating those areas if this were my own home. In my own home, I didn't bother to insulate basement walls with earth on the other side that are under parts of the house that are built on slabs, either, and those walls don't get noticeably cold in the winter. The exterior side earth that is "sheltered" by the slab is similar to how earth bermed walls have lower heat loss compared to exposed walls.

   Bill

3. 
   PLIERS | Mar 06, 2021 07:19pm | #7

   Thanks Bill, I agree with what you are saying that I could probably get away with just hitting the exterior walls. It would certainly be a much easier project for me to finish. What would I use with gap between interior foundation wall and finished floor. Caulk and baseboard?