Basement wall insulation? Advice sought

[Henry W]

I am re-finishing our 70's era faux paneling basement. The drywall is already on the ceiling (75% at least) and I have about half of the paneling off the walls.

The exterior block walls have 1x4 installed on the flat with concrete nails. There is Al foil vapor barrier installed between these 1x4 flats, and I have never seen or noticed any water issues. Well OK that is not quite correct - Hurricane Fran dumped so much water that it came in under the level entry back door and flooded the floor - but other than that we have 13 years of dry basement.

The exterior grade slopes so that the west facing exterior wall is essentially completely exposed, and the north facing wall is about 30% below grade (10% below grade at one end and 50% below grade at the other end).

I can simply install drywall where the panelling was, with no changes.
But my inclination is to add 1x2 furring strips and install 1/2" or 3/4" solid foam insulation panels between them (if such a panel exists). One additional tidbit is that I do need additional furring strips because I am planning on installing pine wainscotting and I need more horizontal backing for that (at the right height).

Does that sound worth it? Any advice on sourcing such foam panels? Any gotchas in my plan?

The basement generally stays warm enough in winter, and cool enough in summer with only minimal HVAC.

Henry

 

[McRabbet]

I had a similar situation in my shop wall facing the front side foundation of the house, but underground. There was some minor efflorescence on the concrete blocks, so I sealed the wall with a coat of Thoroseal and then built a full stud wall 1" away and insulated it with R-13 fiberglass after running my shop receptacle circuits. Never had any moisture problems and the shop stays comfy even in winter. The full stud wall provided adequate room for wiring and the insulation, which 1 x 2 furring strips will not. I was able to attach my wall both top and bottom with conventional double stud plates.

 

[mbolt512]

For what it's worth, here's my two cents.
McRabbet has the right idea, but if you don,t want to go that far I would definitely insulate the above grade walls as block has almost no R-value. The ground temperature generally remains in the mid 50's year-round so the below grade walls aren't quite as important. I'm almost certain you can get 1" and 2" foam panels at Lowe's and the're usually R-8 per inch. I would keep the drywall about an inch off the floor to prevent wicking any moisture from the concrete. Cover the 1" gap with baseboard. Also allow about an 1/8" gap under the base for the same reason, then caulk to floor.
Hope this helps. Good luck

 

[Gotcha6]

Insulating a masonry wall has a wide variety of methods that can be used.
You could drill a hole in the block face & have foam pumped in for an expensive and effective installation, but you'd still have the heat loss through the block webs.
Another method is to purchase metal 'z' channels and fasten them to the wall. You could then install rigid styrofoam between and under the outer flange of the 'z' This method would reduce any cold spots encountered by the first method and would not reduce the overall room dimensions significantly. Wood blocking could be incorporated into the assembly to help with the wainscoting.
The wood stud method would be the ultimate insulation wise, but you'd lose more floor space that way. It would also make wiring and wainscoting installation easier. Just be sure if you do this to leave a gap between the studs and the block wall unless you use ACQ lumber - and use an ACQ sole plate as well.

 

[newtonc]

And if you are going to stud in a wall floor to ceiling,
first make sure you don't have a floating floor.

 

[Steve W]

I've done two rooms in "the cellar" over my life: the first in a house with a mortared fieldstone foundation, the second in a walk-out with a concrete foundation. In the former case, I used the stud wall approach, giving a few inches between the studs and the foundation. In the latter, I framed with 2 x 3's the portion that was against the concrete knee-wall. All were fully-insulated, as cellars in New England can get into the 40s pretty easily in January (these were my radio rooms and were used quite a bit in winter). Both rooms retained heat very well in winter and were comfy in summer (with a dehumidifier).
Be sure, if you're using drywall, to use the new paperless stuff to avoid mold issues in the future. As any New Englander will tell you, there's no such thing as a 100% dry cellar!:no:

 

[cptully]

I have done or helped with three basement rooms so far (two in my parents house and one in my last house). The first room was done with 2x6 studs on the two outside walls to accommodate the 6" fiber glass we had left over from a rental. The result is that this room is now warmer in the winter than any other room in the house and colder in the summer - I grew up in this room and literally kept the heat/ac vents closed down to a crack! The next room was the family room outside the first and it was done with furring strips and solid foam insulation. It is warmer than before but no where near as warm as the room done with 6" fiber glass!

The last room was the basement of my last house (in MD). It too was done with furring strips and solid foam. Resulting in a noticeably more comfortable room. I did have water problems in this house but had already paid to have a french drain with sump pump installed inside and sodium bentonite clay injected in the soil around the house. Sodium bentonite expands as it gets wets. The more water there is in the soil the more it expands and blocks the pores in the soil around the house. The result was that I went from empting my dehumidifier 1-2 times a day to it shutting itself off because the air was too dry!

Since doing these projects I leared a little more about what I did and would probably do it again with 2x4 studs set off from teh wall and isolated from the slab by a rubber membrane.

Chris

 

[steviegwood]

I would insulate with at least the foam board insulation if not studding out the wall and doing fiberglass. To answer the question about getting foam board sheets. Yes it is available in several thicknesses at 84 lumber, Lowes, Home Depot. Most that I have seen is a blue foam board or foil backed. I have found a place locally here that gets plain white Styrofoam sheets in various thicknesses. I purchased 2"x4'x8' sheets for inside my metal 24'x40' shop at $5.00 per sheet. I have no idea the r-value but it certainly has helped with what I have installed so far which is just the roof. Steve