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Discussion Starter · #1 · (Edited)
I basically made the same thread a couple weeks ago but got no real conclusion so hopefully making a simper description will yield a better result.




This is an apt and the tenant found that the bathroom was too cold for temperature code this winter. The bathroom was apparently added over a deck at some point. The crawlspace section where it says 'crawlspace wall' is fully enclosed with 4 block walls. The crawlspace on the left of that is three block walls with the front facing wall being just plywood for exterior storage. On top of the block wall that separates the 2 crawlspaces is a band joist represented by the black piece I drew. That band joist blocks air from the left crawlspace to the right side one. But, as shown by the arrow, air gets right though the spaced decking to under the bathroom. The deck has a roof but it doesn't extend past and minor water also got into the crawlspace.

The crawlspace is unvented, has a concrete floor, and is joined to the main basement with a closed/open 2'X2' hole in the wall.

There were only a few random pieces of insulation in the crawlspace ceiling. So I insulated the three perimeter walls of the crawlspace under the bathroom with unfaced R30 fiberglass after sealing any gaps with greatstuff and caulk. I sealed the section of decking where the arrow is with flexible caulk and insulated the crawlspace ceiling with unfaced R30. They tested the temperature after this and it was still a couple degrees too cold to meet code. So I cut some holes in the bathroom wall and found that they had barely insulated it originally. I rented a cellulose blower but it jammed when used correctly, and when it worked, it would just clog up too soon especially if there were a pipe/wire in the bay. Since it only needed a couple degrees to meet code, I put strips of unfaced fiberglass in the holes in every bay except where the shower tiles are and then patched and painted. At this point, it wasn't cold enough outside to test the temperature again. The tenant said that their contractor friend said the crawlspace should have been done with foam boards instead of unfaced fiberglass.

Owens Corning themselves say right here at around 5:20 that an unvented crawlspace only needs the walls insulated and that unfaced fiberglass can be used:

http://www.youtube.com/watch?v=1czaD4go5JA#t=321


The tenant is mainly concerned about air infiltration and thinks that the spaced decking is the problem and says that 'boards' should be put over the deck. They want foam boards since they're taped together and less likely to leak air even though I had already sealed the entire crawlspace with greatstuff and caulk. I know that the main problem really is that the bathroom walls aren't insulated enough and the only way to fix that is to have a truck-mounted foam sprayer cut in from the exterior and insulate behind the shower walls and all the rest of the bathroom walls. But as mentioned, it wasn't temperature tested after I put strips of fiberglass high and low in every bay of the bathroom except for the shower walls, so it probably meets temperature code as it is.


So what is your take on the unfaced fiberglass? if I put a vapor barrier/retarder over it, isn't it the same as foam boards except that it's actually better because of R30 vs foam boards at around R15? If you think it really needs a vapor barrier/retarder, shouldn't I put one on both sides of the insulation? Because as many have said when it comes to this, single vapor barriers/retarders are only good for the cold/hot season and cause damage for the opposite season - like, if I put a vapor barrier over the fiberglass in the crawlspace ceiling instead of behind it where it would be touching the subfloor, then in the summer, heat from the crawlspace will meet the cold from the bathroom and condense on the outside of the vapor barrier which is okay but in the winter, heat will condense on the side of the vapor barrier facing the joists and moisture will collect in there. Some have suggested a vapor barrier/retarder paint maybe I can paint under the joists with that, put the fiberglass back up and then put a vapor retarder/barrier over the r30, and same for the concrete block walls. ? But I'm trying to convince them more materials and work is overkill anyway though.



And for putting 'boards' over the decking where I already sealed between all the decking with flexible caulk, can you think anything water and airproof besides something pricey like having a truck mounted fiberglass sprayed installation?

What's you take?
Thanks.
 

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Sean
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I am kinda of curious how this is your first post but you did one before... While there is to much information needed that is missing as a general rule of thumb - you have created a mess by using fiberglass under a deck & in the crawl. Sure you might be able to use FG for crawlspace walls, but there are a whole host of other things that should be accounted for before one might just hope that it is a good idea & will work
 

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I am kinda of curious how this is your first post but you did one before...
I can verify there was the same thread before. The problem here is that the tenant wants something different done - foam insulation board @ decking, but the basic technical problem is the bathroom walls weren't insulated correctly, along with whatever unknown air sealing issues for the bath. Every thing else has been a distraction.
 

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I rented a cellulose blower but it jammed when used correctly, and when it worked, it would just clog up too soon especially if there were a pipe/wire in the bay.

....

What's you take?
Thanks.
Get an insulation contractor to blow the walls, and be done with it.
 

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Discussion Starter · #6 · (Edited)
Yeah knocking down the bathroom and rebuilding it isn't going to happen.


While there is too much information needed that is missing as a general rule of thumb - you have created a mess by using fiberglass under a deck & in the crawl. Sure you might be able to use FG for crawlspace walls, but there are a whole host of other things that should be accounted for before one might just hope that it is a good idea & will work
How did FG create a mess? The FG manufacturer Owns Corning suggest unfaced for a crawlspace in the video I posted.


"Get an insulation contractor to blow the walls, and be done with it."

That's last resort if it doesn't meet temperature code when it's really hot/cold out, but the landlord might just pay their heating bill, but all the fiberglass I put in the walls should move the temperature the couple degrees it only needed.


Maybe only put foam boards in the ceiling area below the spaced decking so the FG under it doesn't get wet and loose it's R-value even though I flexible caulked between all those boards? But for that matter, why not just poly sheet or water and air proof paint/sealer between the decking and the FG?

We're just trying to have the tenant satisfied and stop coming up with reasons for their heating/cooling bill to not be paid, like the bathroom has an operable window which, in an existing dwelling doesn't require an exhaust fan but one was installed anyway to not dispute it.
 

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Anytime there is air infiltrating, it will do so with the same moisture content as the ambient air. Moisture can wreak havoc on fiberglass insulation, not merely liquid water. Anytime the FG insulation has lost its fluff, it has lost its R value, and it seems more times than not, it is rendered useless.

The air infiltration (in all locations) must be stopped by whatever means is appropriate for your situation (may involve redoing a specific part of the exterior deck?), which includes many other variables than what you've been able to provide thus far. In other words, it would be best if the situation was evaluated onsite by a competent individual that can provide a proper remedy. Folks here could throw out several viable options, but, as I said, it would be best to look at the full scope of the problem.

Further, are you aware of encapsulating the entire crawlspace area and providing passive conditioned air from the living space above? This in one possible solution out of several, all of which would be best implemented after an onsite evaluation.
 

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Discussion Starter · #8 ·
Anytime there is air infiltrating, it will do so with the same moisture content as the ambient air. Moisture can wreak havoc on fiberglass insulation, not merely liquid water. Anytime the FG insulation has lost its fluff, it has lost its R value, and it seems more times than not, it is rendered useless.

The air infiltration (in all locations) must be stopped by whatever means is appropriate for your situation (may involve redoing a specific part of the exterior deck?), which includes many other variables than what you've been able to provide thus far. In other words, it would be best if the situation was evaluated onsite by a competent individual that can provide a proper remedy. Folks here could throw out several viable options, but, as I said, it would be best to look at the full scope of the problem.

Further, are you aware of encapsulating the entire crawlspace area and providing passive conditioned air from the living space above? This in one possible solution out of several, all of which would be best implemented after an onsite evaluation.
The basement connecting to the crawlspace is also space for other tenants, so adding vents to join it to the bathroom isn't really a good idea hearing people talk or go the bathroom etc. The 2x2' hole in the crawlspace that joins to the basement was screwed shut before I insulated. The basement has a few furnaces that make the basement warm in the winter and it's naturally cool in the summer so I left the 2x2' hole open to the crawlspace.


Regarding the FG getting wet and losing it's R-value, I already sealed everything in the crawlspace with expanding foam and caulk before insulating. Except for the decking area, it's the same as the hundreds of basements I've finished with FG on concrete walls without a vapor barrier on the concrete wall, only the side of the FG facing the finished basement required a vapor barrier. And now that I'm learning more about vapor barriers doesn't make sense to not have a vapor barrier on both sides of the insulation where there is a cold and hot season. Vapor barriers can be very subjective, some say block it on only one side, or both sides, or just retard it, or just let it pass though instead of accumulate.

And for vapor barrier/retarder, even Owens Corning suggest unfaced FG and we're talking a bathroom where one steamy shower is probably 5+ years of vapor in the bathroom and an exhaust fan was also just installed. It's not necessary a damp crawlspace or basement either, just trying to let the tenant know that it didn't have to be done with hundreds of dollars of foam boards plus all the specialty tape and fasteners.

So I think what I'm probably going to do is put a piece of foam insulation only under where the decking is since wood can split and is porous letting possible draft in. I'll put wood sealer underneath the decking boards also, then caulk in the foam board and put the R30 back up. And seal the decking from the outside so water doesn't collect at the bottom of the decking near the foam board and rot the wood.
 

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Discussion Starter · #9 ·
How is it that every foam board with retardant/reflective/barrier face I checked out in the store says it must have an added barrier installed afterwards such as gypsum board, but I've never seen drywall or anything added over these in crawlspaces or heard it mentioned in all the research I've done on it? I have no problem drywalling over it, just curious.
 
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