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k.kuenn 02-21-2011 03:42 PM

Very cold floor
Our floors in the house are very cold. They're wood floors and currently we do not have any insulation in the basement.

Is it effective to insulate the sill plates around the basement walls, or skip that step entirely and just insulate the basement floors? The basement currently is not heated.

And if we do insulate the floors, I would prefer to use extruded foam rather than bats because our ceiling height is not much to write home to :)...but I'm not sure which is more effective on keeping heat upstairs and the floors warmer.

Bud Cline 02-21-2011 04:42 PM


Is it effective to insulate the sill plates around the basement walls,
That's the first thing you should get insulated. You'll noticed a difference from that alone.:)

Daniel Holzman 02-21-2011 05:33 PM

Basement floors are rarely insulated because the floor is in contact with the ground, which is typically not that cold even in the winter. In my area (Boston), the ground below my basement remains at approximately 50 degrees year round, the basement is unheated, so there is little heat loss through the concrete floor. Sills are a totally different story, they are typically in contact with outside air, which again depending on where you live can be quite cold, and if they leak air, they will lose a lot of heat.

Bud Cline 02-21-2011 06:14 PM


OP: "Our floors in the house are very cold. They're wood floors..."
I don't see where anyone is talking about insulating basement floors.:)

Daniel Holzman 02-21-2011 08:27 PM

"or skip that step entirely and just insulate the basement floors".

Bud, I assumed the OP was talking about insulating the basement floor. Least that is what they asked about.

Bud Cline 02-21-2011 08:35 PM


Our floors in the house are very cold. They're wood floors...

operagost 02-22-2011 03:37 PM

Besides insulating the sill plates with foam board (with caulk or spray foam around any gaps), make sure that you don't have any leaks around windows or anything else breaching the wall like sump drains, gas lines, oil filler/vent, dryer vent, sewage, etc. Don't block off supply air to your heating system if you have it though. :no::laughing:

operagost 02-22-2011 03:38 PM

Oh yeah, and you can actually install radiant heating under the subfloor without disturbing your hardwood. You'll want to insulate first, though.

k.kuenn 02-24-2011 10:29 PM

Thanks guys! I've decided definitely to insulate the sill last question. My sill plates are not like the typical pictures that I see online. They're not recessed to where I can stick foam insulation. The sill (or what I thought was the sill) is flush with the cement block wall. So does this mean that technically what I'm looking at is not the sill, but maybe wood that has already enclosed that area? If it is, how would you recommend insulating it? I understand that I need to somehow cover the foam insulation with drywall...but if it's protruding out, that's going to be very tricky.

DexterII 02-25-2011 12:06 PM

Old house? Previous owners? Wondering if someone previously insulated those bays, and then sealed them with blocking between the joists. Is that what it looks like? See if you can find a cupped or twisted joist, where maybe there is enough of a gap that you can see past the end of the blocking.

k.kuenn 02-27-2011 08:39 PM

Thanks Dexter, yes....someone did block them. But it looks like they didn't insulate behind them. Or if they did, it's long gone and disintegrated. Our house was built in the early 30's. Who knows how long those have been closed up. I think we'll go back through and do it well. These come out pretty easy, which makes me think they weren't doing much in the way of insulating.

DexterII 02-28-2011 09:12 AM

No, I doubt that they are doing much in regard to insulation, and, in fact, may be working against you, because, since the heat can't readily get into those cavities, they are probably acting more like coolers. While I suppose that you could simply leave them in place, drill a hole, and fill them with foam, I would opt for removing the blocking, inspect for rot, etc., caulking as needed, insulating, and replacing the blocking. Be mindful of any water pipes in those areas, and insulate on the outside of them well, in order to eliminate any future problems.

YerDugliness 03-08-2011 07:21 PM


Originally Posted by operagost (Post 595880)
Oh yeah, and you can actually install radiant heating under the subfloor without disturbing your hardwood.

I have been dreaming about doing this on my 1920's home in SW Kansas. I wanted to use an electric HWOD unit to provide the heat for whatever fluid I would use in a closed-loop system (some sort of antifreeze would seem appropriate, as the house is unoccupied for a large portion of the winter already).

The problem I encounter is that the businesses I contact want all kind of information that I can't provide....the R value in the walls (I sincerely doubt there is ANY insulation in those walls....they are 8" poured concrete with 1" X 2" firring to which the interior sheetrock is attached around the perimeter of the house and lathe covered interior walls that I KNOW have no insulation in them), the R value in the attic (there is NO attic, it is a flat-roof house, but parts of the house have suspended ceilings so there is some insulation in there on top of the ceiling tiles), that sort of thing. Without those pieces of information I can't seem to get any help from the hydronic support people. To make things even worse, I think I need to design a two-zone system, as 40% of the house has vinyl covered floors and the rest of it has heavily padded carpeting :whistling2: .

Has anyone else ever attempted a project of this sort? I have full access to the joist bays from the basement and have already wired the house with extra circuitry for electric HWOD units and pumps. It seems like it ought to be fairly simple, but......I'm certainly not an expert at anything of this sort.

Cheers from Dugly :cool:

shumakerscott 03-13-2011 12:47 AM

I used this site when I put my system in. Great information.
dorf dude...

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