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KatieAK 11-01-2009 02:03 PM

How to (retrofit) insulate/air seal cantilever with hot water pipes in it?
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We've got a 3' deep/wide cantilevered space on our upper level, with hot water baseboard running on the far end (along the entire wall of that living room space), meaning that the hot water pipes drop down into the cantilevered space at the far end of the cantilever. We are starting some (retrofit) insulation work on the concrete-block walls of the tuck-under garage, which is under the living room that has the cantilever (so, one side-wall of the garage is the point from which the cantilever extends out above), and realize that we should try to address the cantilever, if possible, at this point as well. We opened the ceiling drywall of the garage in two places along the wall with the cantilever, and see that 1) there's no blocking above the foundation/garage wall to air seal/insulate from the cantilever... and 2) the cantilever appears to not be properly air sealed or insulated from down-below -- I can feel metal (soffit?) on the bottom, with cold air coming up in places. There's fiberglass in the cantilever cavities, with facing towards the bottom, but as described, it's not air sealed very well.

My question is how to best address the worst of the cantilever situation, in terms of air-sealing and insulation, without tearing out the soffit from outside (which we're not ready to do at this point), and without creating problems with freeze-ups for those pipes at the far end of the cantilever?

My first thought is to add rigid foam sections (sealed w/caulk) above the garage/foundation wall, to act as block between the cantilever space and the rest of the floor/ceiling space. My concern is that that method could pose more problems for the cantilever pipes (if it would be blocking heat from getting out there - which I know isn't energy-efficient, but possibly has been happening thus far, as the garage is heated space (it's on the downstairs loop, which also runs into the downstairs living space - bad layout, I know). Any suggestions on how to (better) insulate/air seal the cantilever from the side (accessing from the garage ceiling, not from below by removing the soffit covering), taking into consideration the pipes out there? I've been warned by more than one plumber to NOT use spray foam insulation right up to the pipes, as it makes it darn near impossible to get to/work on them, if/when needed... so, in my mind that would rule out spraying in foam that way (am I correct in this assumption?). Can I just leave the cantilever as-is for now (w/ fiberglass in there, but poorly air-sealed) and add the foam blocking, and then later address the actual cantilever space (from below by removing the soffit), or is that a bad idea in terms of the cantilever pipes?

[Forgot to mention earlier, but there hasn't been an issue w/ pipes freezing out there -- once, years ago (previous owner), but no problems in the 3+ years we've owned the home.]

Thanks in advance for your feedback/suggestions -- I'm new to this (but learning)!

Anchorage, AK (currently in the teens)

NOTE: I added photos showing first the exterior of the cantilever, then photos of the opening in garage ceiling that shows lack of blocking to cantilever, as well as photos back into cavities between ceiling/floor joists that run out into cantilever -- showing existing insulation (which is showing dirt from air flow by the way, but no moisture/mold where I can see it, unless the black is mold and not dirt...?!)

yuri 11-01-2009 04:08 PM

Post a bunch of pics. They are worth 1000 words.

KatieAK 11-01-2009 06:19 PM

Good idea -- I'm new to this, so it will be my first time posting pics... but I'll go try!

yuri 11-01-2009 06:53 PM

Click on "go advanced" in the quick reply box. The go to "manage attachments" and follow the instructions. Or post them on photobucket or imageshack and put the links here. Quite a few contractors and building guys read these posts.

KatieAK 11-01-2009 07:41 PM

Thanks, Yuri - I did add photo attachments to original post.

Another update/question - I've for sure identified one 'cavity' out in the cantilever that for sure has pipes in it (coming down from the baseboard along that wall in LR above), and that is, not surprisingly, the one place we know there was a freeze-up (5+ years ago, no problems since). IF that is the only cavity that has pipes in it, then perhaps would it make sense to block the other cavities, but not that one with the pipes (to theoretically keep some potential warm air moving in there from the adjacent floor/ceiling space above the garage)? I'm wary of pulling out the fiberglass in all those cantilever cavities now since I'm not ready to deal full-force with the air-sealing out there from below... but it seems that's my only way to see out to the end of the cantilever and determine exactly where the pipes run from that LR baseboard unit that drop down out there.

Something else I didn't explain well in the original post... the cantilever space runs BEYOND the depth of the garage, another 10 ft. or so towards the back of the house, into/above downstairs finished living space. So, our 'easy access' through the garage ceiling (if we cut it out) will only gain us access to ~ 2/3 of the cantilever cavities -- for purposes of blocking it off from the rest of the house... so that back 1/3 we'll likely not touch, seeing we don't want to tear up finished ceilings to get to it -- we'd only access that from below in the soffit, if/when we get to that.

yuri 11-01-2009 08:15 PM

Hang in there for a couple days, I am not a carpenter/builder but I am sure some of our other guys may have some advice for you.:thumbsup:

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