Vapor Barrier or not to Vapor Barrier?

Started by MelFol, January 03, 2011, 09:36:56 PM

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MelFol

#25
Muldoon: The rules would stay the same, but given the low usage would you get a decent return on investment by doing a perfect job or super-insulating? Seems to me there wouldn't be enough temp differential most of the year to matter, especially if you use 15# felt so the wall can breathe a little.  On the other hand, if you intend to use it more in the future....
Here is a graphic from a previous thread that may help as it maps your area:



Texas Tornado

"closed cell foam" Is this a product that would or could or should be used in a area that has high humidity and cold weather? Is this something for just the ceiling or is it a product for the wall cavity as well?
Can this be done by a DIY or do you have to hire a professional to do it?
TT


Canvasman


Here is the ceiling, and in the background my walls. Done in closed cell foam, this is northern wisconsin. I can tell you that it has been hot here, it was 91 outside and 74 in the house in afternoon with no air conditioning. I would not try spraying this myself, cheap enough to hire someone. My ceiling 6inches, walls 3.5, and 2 basement walls and band joist, 3.5 inches 7300.00 for 864 sqft home. You have to have mixture right, or it doesn't stick or expand correctly.

CjAl

$7300 is "cheap enough"? boy you have different ideas then i do.

CjAl

i am building in that "vapor barrier on exterior" zone. i would like to know how that works with the roof.  plastic under felt? what about the air gap in the rafters, still need it?


Canvasman

$7300 is cheap. When you look into buying 55 gallon drums of material, compressor, hoses, spray gun, heater to keep material at correct temp. and the time it takes to do the job. Not to mention experience to install correctly.

CjAl

i know the price of the setup. i have looked into buildi.g or buying a rig. but there is still nothing cheap about $7300

MountainDon

Quotewhat about the air gap in the rafters, still need it?

IF "sufficient" spray foam insulation is used on the underside of the roof sheathing moisture will not be able to condense on the underside of the roof/sheathing; therefore no air space and no venting will be required.  The thickness varies with climate.
Just because something has been done and has not failed, doesn't mean it is good design.