Looking to put 1×6 T&G Knotty pine in cathedral ceiling in a new house. Boards will have a coat of poly eurathane on both sides before being installed. Ceiling has closed foam insulation between rafters. Was going to install boards directly onto rafters. Wondering if I should put some type of barrier between wood ceiling and rafters? Hoping to get wood acclimated and watch humidity as best as possible to keep movement to a minimum in the wood ceiling.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Learn more about the benefits and compliance details for the DOE's new water heater energy-efficiency standards.
Featured Video
SawStop's Portable Tablesaw is Bigger and Better Than BeforeHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
How thick is your closed cell foam in ceiling?
Closed cell foam that is installed properly at 3" or more has a perm rating of less than 1.0 wihch is considered a vapor barrier. You're smart to seal both sides of your T&G pine and monitor your relative humidity during acclimation, install, and after. You should also monitor your framing and finish material for moisture contents (M.C.) Finish wood materials generally acclimate to around 5-6% M.C. in a steady 35-40% R.H. which is considered an average, healthy range.
WHAT?
deadnuts wrote:
Closed cell foam that is installed properly at 3" or more has a perm rating of less than 1.0 wihch is considered a vapor barrier.
deadnuts wrote:
Closed cell foam that is installed properly at 3" or more has a perm rating of less than 1.0 wihch is considered a vapor barrier.
what kind of closed cell foam are you using? getting your facts of houzz???
2lb closed cell at 1.5" meets class II and is considered to meet all requirements for a vapor barrier.
Mason Knowles*. He writes in Sprayfoam.com:
"Vapor barriers are not required with closed cell foam in all climate areas of the US according to the 2003 and 2006 IBC and IRC codes. Closed cell sprayfoam installed at a 3 inch thickness has a perm rating of less than 1.0 which is described in the codes as a vapor retarder. In the 2007 new supplement, 3 types of vapor retarders are introduced, closed cell sprayfoam would be typed as a class II vapor retarder according to the new codes and again does not require an additional vapor retarder in all climate areas in the US."
* Mason Knowles has "more than 40 years of experience in the polyurethane foam industry as a contractor, material supplier/manufacturer,equipment manufacturer and trade association professionalhas provided Mason Knowles with unique qualifications to assist with a wide variety of services..."
You can look up Mason Knowles Constulting for your spray foam concerns (he has a phone # and address) and ask him yourself. However, I think Mason's credentials speak for themselves. But as usual Mark122 has... well, nothing. No credentials, no website, no contact info, no published body of work to speak to at all. Just more knee jerk rhetoric.
Given your lack of credentials, what sage advice to you offer the O.P. in this situation?
oh dumbnuts...
next time you are going to regurgitate, check what your spewing. so you assume because you are quoting someone that you assimilate their credentials? you are a clown.
http://www.icynene.com/en-us/architects/products/product-portfolio/md-c-200
Key Product Features
Aged Thermal Resistance: 6.6 per inch *
Construction Types: I - V
Core Density: 2.4lb.
Evaluated and listed by ABAA as an air barrier material
Class II vapor retarder at 1.5” thickness
Meets FEMA criteria for resisting water absorption
Compliant to California Department of Public Health EHLB v1.1-2010 Emissions Specification Section 01350
Actually, I assimilate their knowledge; not their credentials. I have my own credentials which are listed on my website. They include an architectural degree from a well respected university. What's yours?
For the record, here's what Martin Holladay of Greeen Building Advisor has to say with regard to your icynene industry reference...
http://www.greenbuildingadvisor.com/blogs/dept/musings/it-s-ok-skimp-insulation-icynene-says
BTW, you've reference 2.4 lb density, but quoted 2.0 earlier. Fact of the matter is that installed density is inconsistent due to many field variables including installer experience, weather, equipment maintaince etc. Martin Holladay is on record reommmending 2.5" of closed cell in order to achieve a class II perm rating. That makes two industry professionals on record withing .5" of each other. I'll default to the great due to field inconsistencies. Further, I believe most cases where closed cell is sprayed for unvented roof assemblies it will be sprayed in lifts exceeding this thickness, making your argument a moot point.
So your an archy???
I will give you the fact that you have some of the characteristics of some architects. Out of touch with practical construction, over zealous about theoretical conditions and a blind obsession with "being right" even when your not.
Martin's blog post references open cell. different animal all together.
2.4lb is what everyone calls 2lb, slow rise, or closed cell. aside from the previous manufactures spec sheet you have already looked at here are a few more:
http://www.certainteed.com/resources/30-50-011.pdf
http://www.demilec.com/documents/Tech-Library/Heatlok/Heatlok-Soy-200-Plus-TDS-062415.pdf
to be more specific, when using demilce you only need 1.42'' to meet class II
simply by dismissing a point and labeling it moot because your wrong just goes to show your characteristics mentioned above.
in case technical information is to difficult for you to process, let me set a practical scenario.
a contractor sprays the exterior walls of a home (following manufacturer guidelines) and bypasses the outdated, inefficient plastic vapor barrier used commonly where required. Inspection time comes, and the official points out that there is no vapor barrier installed as he is accustomed seeing. the contractor then describes his process and proceeds to show the inspector how he has met and or exceeded the barrier requirements.
what will the official require to be satisfied with the contractors rebuttal? a link to a few educated guys speaking to their biased opinion of a product, or a manufacturers techincal sheet? since you have a history of not being able to keep on track and chasing rabitt trails, let me answer that for your. they will 100% of the time go the the manufacturers technical data, and if more information is required, they will request more about the manufacturers claims, not online blogs.
the reason for the back and forth about the matter is simple. you stated " Closed cell foam that is installed properly at 3" or more has a perm rating of less than 1.0 wihch is considered a vapor barrier (at least twice the actual amount required)
great web site by the way...whenever your middle school web designer goes on christmas break, tell him to call me I need mine revamped.
Come inspection time, I wouldn't have a problem with meeting class II vapor retarder requirement. You'd be the one on the light side of that issue. Probably just why you keep that commonly used roll of poly in the beater of a station wagon you call your work truck.
Note: You have to actually have a website in order to revamp it.
Rabbit trails!!!
ACTUALLY we are not required an interior vapor barrier.
your vehicle remark is a perfect example of your views.
in your head, a big expensive truck, eloquent vocabulary equates competence. everyone else just sees a washed out architect wanna be turned remodeler cause he couldnt hack it in school.
too much???
im officially board with your inability to argue an issue without licking your narcissistic injuries.
Hey sonny, so do you want all posters to fill out a form (showing all contact info, education history, web address, email and "published" work) before they dare dissagree or point out ridiculous comments made by the webs greatest genius to every type a letter?
I assume you are implying that you feel credidted by contact information, website and some sort of published body of work (where?)
Stain the tongues before you install the T&G.
Acclimating a necessity...
You don't mention what part of the country your house is located - will the space be conditioned close to final living condtions when you install/acclimate the material? 1x6 pine can move quite a bit - I assume it's kiln dried. I would sticker the material to allow ventilation all around the pieces - It won't do much good if you just stack the material on top of itself in a big pile.
Great idea to put at least one layer of poly before install...
I used vertical 1x8 cedar shiplap siding on a project exterior that was installed in the NW winter time...by the time summer rolled around, you could have tossed a cat through some of the joints - very disheartening. Fortunately, it was all pre-stained, otherwise we would have had to restain the house. Never used it again...
Did same ceiling 3 years ago
Southern New England. 1 x 6 white oak directly onto 2 x10's with fiberglass insulation with kraft paper. Mill assured me wood was good and dry. I left it in the room mid October for two weeks. I put a water based satin poly on it, two coats after it was up so only one side, one purchased at a woodworking shop (the minwax poly seemed to change the color too much on my sample board). I cant remember the name of product but I'd recognize it if i heard it or saw it again. Anyway, joints have all stay real tight. Maybe by end of winter u can see a few hairline gaps but closes right back up. How much moisture depend I guess on roof construction but nothing is getting through your close cell foam. Pine is a bit of a different animal than oak but.......i wouldnt even bother putting sealer on back