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Discussion Starter · #1 ·
A tenant found their bathroom was colder than code this Winter.

The bathroom was either added when a space was divided into more units or it was originally built wrong because it's on a deck subfloor and the deck is exterior besides the bathroom section - air comes through the outside decking and into the crawl space under the bathroom. In the crawl space, there's a non-perimeter foundation wall with a ledger on it for the deck frame that separates 2'x6' of the deck over the crawlspace from the rest of the deck. In other words, if you look up in the crawl space, there's 2'x 6' of decking letting air in but the rest of the deck and joist bays are sealed off from the crawlspace with a ledger on top of a non-perimeter foundation.

The crawl space is unvented and is connected to the main basement with a 2'x2' open/closed hole in the wall. The crawlspace floor is concrete.

We wanted an inexpensive way to get the bathroom warmer. Without something like spraying a fiberglass boat-type coating over the deck boards to seal the top from water and air, we caulked between the 2'x6' decking boards from underneath in the crawlspace. Since it had the highest R value, we insulated the floor joists under the bathroom with unfaced R30 fiberglass and the 3 exterior block walls of the crawlspace.

The temperature was still a couple degrees too cold after this. I figured there must not be enough insulation in the walls, cut holes high and mid level in the bathroom bays and found that they only put pieces of insulation here and there in the walls. I pumped cellulose into the holes, but the rental machine jammed when used properly and even when it worked, it would just clog up the bays too soon and not fill them especially if there were a pipe or wire in the bay. So we then put pieces of unfaced R30 fiberglass down into the holes (the walls already had a few coats of vapor barrier glossy latex paint). Then we patch and painted but the weather turned and it wasn't cold enough to temperature test again.

Now the tenant is saying that the crawlspace should have been done with foam boards instead of fiberglass but according to fiberglass manufacturers and other credible sources, unfaced batts without a vapor barrier can be used in an unvented crawlspace especially with the hole in the wall leading to the main basement left open and with a concrete floor. The tenant is also saying that the entire exterior deck should have boards put over it to keep air from coming in but only 2' of the deck is over the crawlspace and was already sealed with caulk and insulated with r30.

It should meet temperature code next Winter and in the Summer, but to satisfy the tenant, I'm thinking that a poly vapor barrier in addition to the fiberglass would give the same if not much better affect (because of the higher R value of R30 fiberglass compared to panels) than using panels even if the panels have a retardant face that reflects heat/cool.

If it still doesn't meet temperature code, I know the problem is the bathroom walls not being insulated enough but the only option for that seems to be getting a truck-mounted foam sprayer and cutting in from behind the exterior wood clap boards instead of cutting holes inside the bathroom. For now, we just need to convincing the tenant that the fiberglass doesn't need to be replaced with foam boards and putting 'boards' over the entire exterior deck isn't necessary.

So, must I add a vapor barrier? And will it give a better or at least the same affect as panel boards if not better since it's R30 fiberglass already?

There's wires in the crawlspace joists, so if a vapor barrier is necessary, I'm supposed to remove the fiberglass from the floor joists and put the vapor barrier on the subfloor and joists and staple it and tape over the seams and staples, and then put the unfaced fiberglass back in, correct? In other words, follow the contour of the joists and subfloor with the vapor barrier by putting the plastic right on the wood joists and subfloor, correct? And for the crawlspace walls, just put a poly vapor barrier over the unfaced fiberglass? There's also plumbing pipes and a dryer duct in there I need to work the barrier around, so use tyvek or silver aluminum tape? Add a poly vapor over the concrete floor for good measure?

If even necessary, what should be used that won't look ridiculous to seal the 2' of exterior decking from the crawlspace besides the caulk that was used underneath? Like, can I brush on a non-slip fiberglass boat-type coating after filling all the 1/4" decking board gaps with flexible caulk? It should be kept uniform for the entire deck besides just over the 2' section, so trying to find something inexpensive to cover the whole deck if it's even necessary.

Thanks.
 

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Discussion Starter · #3 ·
basically all I'm asking is if unfaced r30 needs a vapor barrier in this case and how to install it. If it's as good if not better than foam boards the tenant is pushing for.

And how to seal over the decking if the caulk isn't good enough.
 

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I think that you had better post a lot of pictures for this one.
Certain types of paint can be used as a vapour barrier.
As for the floor, viynle floor maybe.
 

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Discussion Starter · #5 · (Edited)
you mean vinyl floor as a vapor barrier on the crawlspace floor? Someone might slip on that on the deck. maybe a roll on truck liner to seal over the deck boards after filling in between all them with flexible caulk? Would probably add up in cost though. Trying to convince them r30 doubled up under the porch with the boards already sealed with caulk is good enough and no need to 'put boards over everything'.

It's all insulated now and can't really see what's going on, might be able to get some pictures but hoping to avoid all that.



only where the blue arrows are could air get into the crawlspace, the ledger blocks off the rest of the deck joists air flow into that crawl space.
 

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Much opf the US doesn't require a vapor barrier - just a vapor retarder. Think paint. It doesn't have to be expensive paint, either.

More importantly, making changes willy nilly wastes a lot of time and money, and you aren't guaranteed to have fixed the problem. The very first step should be to track down all sources of air leakage and tighten the bathroom up. All the plumbing penetrations are obvious sources.

Then get a non-contact thermometer to measure wall temps to find areas with "cold" issues, and use that to plan your insulation upgrades. R30 on a floor isn't going to do much good in most cases.
 

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Discussion Starter · #8 ·
This spaced decking... I'm assuming it's under roof and well protected from rain?
there is a roof over it, but it doesn't extend past, but still, it's obvious the house wasn't built like that. The foundation wall with the ledger should be under the end of the bathroom or they should have added one when they added the bathroom over the porch, but it must have been the same guys who opted not to insulate nearly half the bathroom walls that didn't temp jack the deck up and cut the joists to and add in another foundation wall with ledger/rim joists. It was already insulated in like the 50's or something, rain eventually made the batts fall down or soaked. They were held up and enclosed in some sort of heavy cardboard that was nailed over the joists in the crawlspace like sheetrock, but most of the crawlspace wasn't insulated.



but, hdavis, if a vapor retarder is needed, how will I apply that to the crawlsapce? can I just pull all the unfaced r30 out the floor joists and paint it with vapor retarder/barrier paint and re-install the r30? And then just 6ml poly barrier over the crawlspace walls that have r30? I don't see hoe R30! 'isn't doing much good'.


the tenant thinks 'boards' should be put over the deck to stop drafts and their friend said foam boards needed to have been used in place of r30 we're trying to convince them is unnecessary if so.

thanks
 

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Discussion Starter · #9 ·
don't see the option to edit post for some reason. Just wanted to ad they could have just put the bathroom wall over the existing ledger foundation in the crawlspace, but that's neither here nor there now.
 

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but, hdavis, if a vapor retarder is needed, how will I apply that to the crawlsapce? can I just pull all the unfaced r30 out the floor joists and paint it with vapor retarder/barrier paint and re-install the r30? And then just 6ml poly barrier over the crawlspace walls that have r30? I don't see hoe R30! 'isn't doing much good'.
Pull it out, air seal. paint, put it back up.

Insulating a floor to r30 doesn't do much because very little of the heat is lost through the floor.
 

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maybe you should make the crawl space a conditioned space and insulate the perimeter
walls rather than the floor.
 

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Discussion Starter · #12 · (Edited)
Pull it out, air seal. paint, put it back up.

Insulating a floor to r30 doesn't do much because very little of the heat is lost through the floor.
But cold comes in from the floor/crawl, at least that's what the tenant thinks even with doubled up r30 on the entire crawlspace except the floor. And if it's because heat rises you say that, in the summer, they might say it's too hot.


So for the crawlspace ceiling, air seal with 6ml poly sheet stapled in between the joists and wrapping around all the joists then tape over the staples and seams with tyvek/silver aluminum tape? Or you just mean caulk/great stuff seal the bathroom subfloor from the crawlspace and then paint it with a specialty barrier paint and put the unfaced r30 in last?

Just put poly over the r30 on the walls since the hot side is the actual crawlspace and where condensation would build, correct?


"maybe you should make the crawl space a conditioned space and insulate the perimeter
walls rather than the floor."


I already insulated the walls and ceiling of the crawl. I didn't however extend the wall insulation 2' onto the floor but I have extra r30 there I'll do that with.
edit: I think you meant floor as in the bathroom floor, not the crawl space floor. At this point, we're just trying to convince the tenant that it's as good as it gets.
 

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The project was done in a completely incorrect way...any fix is just a band aid over a cut that needs stitches. From what I can make of it, the only real fix is to tear out the bathroom and build it to today's standards. You can likely save money by reusing some of the fixtures, but you're digging for an el-cheapo way to fix a bigger problem of a bathroom added on in a crap way. Just my opinion, but you've spent time and money already that could have gone into a true fix.
 

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Heat doesn't rise, warm air rises. Heat radiates out in all directions from its source so there can just as much heat loss through the floor as through the walls and ceiling.
 

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" Heat transfer always occurs from a region of high temperature to another region of lower temperature" doesn't say anything about "heat" rising but rather the materials that are being heated expanding and becoming less dense making them rise and the cooler more dense mass falling. I attended a Gord Cooke seminar some years ago where he talks about this. I wish I could find some of his info on it.
 

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Discussion Starter · #17 · (Edited)
The project was done in a completely incorrect way...any fix is just a band aid over a cut that needs stitches. From what I can make of it, the only real fix is to tear out the bathroom and build it to today's standards. You can likely save money by reusing some of the fixtures, but you're digging for an el-cheapo way to fix a bigger problem of a bathroom added on in a crap way. Just my opinion, but you've spent time and money already that could have gone into a true fix.
Not that it's going to happen, but how is pumping expanding foam into the walls for insulation and just extending the bathroom wall to be over that black ledger board I drew not todays standards instead of tearing down and rebuilding the bathroom?

Anyway, so does it need a vapor barrier? Foam boards instead of unfaced r30 with a barrier? Can just paint on a barrier to the crawlspace ceiling behind the r30 and then poly vapor barrier over the r30 on the walls?


Then, to satisfy the tenants request for 'boards' over the decking to prevent air flow, what do you suggest? Just tell them that the vapor barrier makes it airtight?

Rust-O-Leum Deck and Concrete Restore kind of makes wood look like composite decking is 10X thicker than paint and lasts up to 12 years but is not waterproof and requires the deck be stripped and sanded before applying which is over budget. I mean, I can't I just caulk in between all the decking from top and bottom with flexible caulk and paint an airtight barrier paint under the deck? It would trap moisture at the bottom of the decking, but I can't think of anything now besides putting plywood over the whole deck and having someone spray a fiberglass gel coat which is over budget.
 

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You my friend need to look up several definitions...vapor barrier, vapor retarder, air sealing, and try to understand how heat moves, through conduction, convection and radiation and apply that to your problem. Also do not forget about vapor diffsions and the affect of permeability of different materials and assemblies have on the overall structure.

How is the rest of the bathroom detailed? What is the vapor barrier/ retarder? what is the air sealing technique and are those two items handled in the same plane with the same material or are they handled separately?

I'm not fully understand your description of the situation. Is this a porch or deck someone converted into conditioned space? Are there actual 1x or 5/4 deck boards with gaps in between for the bathroom subfloor/finished floor?

What climate zone is this bathroom located in?
 

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Only two ways to make the floor warm. One is to build a drop under the floor and heat the area below the floor. Remove the insulation from the floor and put it in the new dropped framework. The other way is to use a heated floor system. They make them in electric so you can install them independent of the heating system. Cover the infloor heating with tile or some other flooring that will transfer the heat to the room. Nothing worse than a cold bathroom.
 

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To prevent heat escape you have to insulate under the slab, along side of foundation perimeter, etc.

I'm doing an addition now, and we put R-40 foam under the slab, 2' down along exterior, and come up to the top of foundation.
 

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