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The subfloors my from the floor above the basement is not plywood. It is made up of individual boards installed diagonally. Combine the unevenness of this subfloor design with nails that are popping and through and my own flaws cutting the xps, I wind up using a lot of caulk. I think it might just be easier to foam all the edges with the stuff in the can.
How are you cutting the xps? I was using my tablesaw for 2" foam and they seemed to be coming out almost perfect.
 

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IMHO, caulk the wood joints before canned foam at the rims to stop infiltration of summer moisture/air infiltrating - wetting the XPS as it will hold moisture much longer than after the wood dries out. With a double facing, you also stop winter condensation on the XPS inside face (if not thick enough) right through air permeable fg or Roxul---though this may dissipate due to the surrounding air; http://www.diychatroom.com/f103/insulate-rim-joists-canned-spray-foam-roxul-307313/ Maybe it's not that important, IMO, I'd spend the extra time.

BSC (IN 2002) also recommended foil-faced foam board on the wood rims as an interior fix; pp. 7, 8, and 9, here- pp.8- top of second column, yet notice Fig.15, either or- maybe it didn't get proof-read...; http://buildingscience.com/sites/default/files/migrate/pdf/BA-0202_Basement_Insulation.pdf

In a later (2007)actual field study, not a simulation or analysis, I found (topic of my searching for) the warm below-grade temps of the soil; few problems with most insulation types, other than solid plastic wrapped FG. or possibly poly sheet on inside at drywall during summer, especially with AC in a lot of U.S., not southern Canada- and that this was an unoccupied house and we don’t know the basement RH. ( eg. Kitchener- check their HDD compared to yours);

Slashing a vapor barrier does nothing as it is area weighed (surface area)- much different from an air barrier; http://www.ecohome.net/guide/difference-between-air-barriers-vapour-barriers


Using 3 coldest months average temps for your location; https://www.currentresults.com/Weather/New-York/Places/new-york-city-temperatures-by-month-average.php
At 68*F in basement w. R-5 + 15R = concrete wall above grade and 6" down at 43.25*F safe to room RH of 41%...................... with R-10 XPS and 15R cavity, 48.2*F and 49%Relative Humidity. Though the plastic drainage board may not be conducting full temp to inside, so both temps/RH would change at the inside rigid board from interior RH. ADA the drywall; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/, use acoustic sealant at perimeters, duct tape/mastic at seams as the board does shrink/change with temps...


Gary
 

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Discussion Starter #23
Hey everyone. Things have been going well in the basement. After listening to everyone's advice, I decided to go with the 1" xps and R15 Roxul. Propping up each board for 12 hours while waiting for the glue to dry was a pain, but I figured out a system using 2x4s.

I was surprised that the 3M red construction tape has NOT held up. It stuck well in the beginning, but lots of air bubbles appeared a couple weeks later. The tape has not peeled off, but I hear a wrinkling/popping sound when I run my fingers along the tape. I've since learned that Owens Corning makes a tape specifically for xps, so I might go over the red tape with the Owens Corning stuff if I can find where to buy it.

I have a new question though. I have a part of my foundation that sticks out to add extra support for the main beam spanning my basement. I insulated and framed around it on the family room side of the basement, but do you think I need to do so in the utility room? I only ask because that would leave very little space between that bump out and my furnace.
 

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How about just boxing it in with XPS and then gluing the drywall to that?

Bud
 
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