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Basement Finishing and Renovations Has it been 2 years already? Time to work on finishing the basement into some extra living space.


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Old 2013-10-05, 12:44 AM
ottawa ottawa is offline
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Default Kraft backed fibreglass? Also, options?

So I had to take down a section of wall for a crack repair in the unfinished part of my basement. I guess is the basement is insulated to late-70s code, it's only the top 4', maybe 3.5" of kraft-faced fibreglass then drywall. Chunks of fibreglass stuck behind the 2x3s top and bottom.

Here are some pictures. https://picasaweb.google.com/1129320...eat=directlink

Essentially it's 1x4s nailed to the concrete vertically with 6" wide plastic behind, then 2x3s horizontally probably 24" OC. Kraft-backed 23" wide fibreglass between the 2x3s, overlapped, with a 6" wide strip of plastic on top of any seams that aren't on wood (so vertically). I'm estimating 3"-3.5" of fibreglass (1x4+3x2).

Overall, not very good.

What I would do in a perfect world is take it all down, put 4" Styrofoam in the headers with caulking/foam around, then put Styrofoam or Roxul Comfortboard against the concrete and build a 2x4 wall filled with Roxul or fibreglass, full vapour barrier, then drywall. Right?

However it's not a perfect world. I don't have time to do all that this year, and there's no budget for it. I know if I start it I will be half done when winter comes and I'll have made it worse. So in practice I'm thinking maybe I can restore it to what (inadequate) level was there. Spray foam across top and bottom, put in 3-3.5" of faced insulation, then put the drywall back. And do it right in Spring 2014.

I can't find faced fibreglass to fit the space. Perhaps it's not sold here (it's on the manufacturers' sites) but made for the milder southern US? Owens Corning (Canada) lists an R-12 (3.5") in 23x47" but (a) it's not faced, and (b) it covers 135ft^2! I think I need 16ft^2.

I did find fibreglass insulation with built-in vapour barrier at lowes.ca but it's 50'x3'xR-12 for $93.60! A little too much for me. Or without vapour barrier (I think) 47"x23"x3.5" sounds almost perfect but it's $55.89 so way more than I need. And then I'd need a vapour barrier?

I could use EPS boards but if I need about 3.5" (1.5" then 2") of 2x8' it's going to cost $19+$25=$44 which is almost as much as that 150ft^2 of fibreglass costs (admittedly less work with EPS).

A pack of Roxul Comfortboard is $48 for 6 2x4' sheets. Maybe I could put two each top and bottom (they're 1.5" thick)? Then reuse it when I do the right job?

Given my constraints, do any of these solutions provide any benefit over just sealing the 2x3s top and bottom and putting the drywall back up (i.e. no insulation)? I hate the idea of doing it but I'm also being realistic about my ambitions for 2013.

I admit I haven't priced having this job done professionally. It's close enough 8' high and about 20' of exterior wall (a 16' wall and the first 4' of the next wall, then it's interior to the neighbour). I assume we're talking on the order of $1000 to do 20' of headers and wall to R20. No services at all in this wall, just in the header there's a fresh air intake and elsewhere a dryer vent (opposite ends of course) and a faucet. Not asking for a quote (there's no budget), just wanting to confirm it's an expensive job.

Thanks!
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Old 2013-10-09, 08:25 AM
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It would be fine if you did nothing.

Drywall is $7.50 a sheet at Lowes. Putting up a half sheet would be ok - you may get a little condensation behind it but that wouldn't hurt anything.

Air sealing and insulating the header areas will save a bunch of heat dollars. That is a good winter project because you can feel the air leaks. A few tubes of latex caulk for joints and cracks and canned foam for big holes is all you need.
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Old 2013-10-28, 12:20 PM
ottawa ottawa is offline
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Great thanks, I was thinking (hoping ) that might be the case. Presumably if the rest of the wall were R-20 right to the floor, with proper thermal break, vapour barriers, and a gasket on the floor, it would be more significant for one part to be under-insulated.

I actually managed to get the half sheet off the wall without too much damage, so I can re-use it for this temporary cover.

I assume I should run Great Stuff foam across the top to fill the gap between the top 2x3 and the concrete, since it looks like there's potential for cold air to spill down through the inadequate header fibreglass? If that's true, should I also run it up the two sides of this area? But perhaps leave the bottom 2x3 with the gap behind it? My logic on the last is that if I fill it then the space is going to be relatively airtight to any condensation will be trapped. If I leave it open, then any condensation on the wall can at least slowly run down and out, and any air that gets in their through the bottom gap is at least warmish indoor air and not new cold air from outside.

Does that make sense or should I foam more (or less)? Not sure I'll be able to do the header over the winter, so it may be spring before I can get to it. And did you mean pull out the backed fibreglass from the headers (and replace with 4" of EPS)?

Thanks again!
=aw
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Old 2013-10-28, 12:55 PM
oakvillehomeowner oakvillehomeowner is offline
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if you can get a tigerfoam kit up there you might be able to do all of your joist cavities for a reasonable cost.
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Old 2013-11-03, 10:44 AM
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Thanks, I guess that's possible but I only have 20' of header (16' wall plus 4' along one side) so at 3" deep (R-20) and say 8" high, ignoring the headers themselves that's <4ft³ of joist cavities. Which makes $465 for 16ft³ a bit expensive. I suppose I could try to do the whole wall too (which would be, what, 20'x8'x3"?) at the same time but not sure about that.

In any case, I can't do anything ambitious before spring 2014. For now, should I put Great Stuff between the 2x3 and top of concrete wall, to reduce air spill in that section? And if so, do I also go down each side of that space, if I'm not putting in new fibreglass? And if I should do both those things, is it wise to leave the bottom 2x3 with that air gap behind it, to make sure any condensation can get out?

Thanks!
=aw
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Old 2013-11-06, 07:21 PM
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I would not seal up these edges - you likely have moisture behind the drywall and you want it to escape and not freeze as it gets colder
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Old 2013-11-06, 07:26 PM
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Thanks. Not even the top edge? I was planning to leave the bottom open but I can see a case for the sides too.

=aw
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Old 2013-11-07, 04:34 PM
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Not essential but wont really hurt anything if you do.
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