In researching closed cell spray foam in conventionally framed walls and under conventional roof decks, I've come across numerous warnings about roof and wall sheathing rot because the CC Foam prevents inward drying.  I am on the Gulf Coast, so that's a significant consideration here.  Yet, in all my research on SIP house construction, I never see any discussion of this issue, or any warnings.  Surely, the outer skin, at least in Polyurethane SIPS, and probably in EPS SIPS, is hindered from inward drying to at least the same degree as a roof deck with CC Foam underneath?  Is there something I'm missing here?  Are the drying mechanisms any different with SIPS, or is there some step taken with a SIP roof that can't be implemented on a conventional roof with CC spray foam underneath?

yes the mechanisms are different--the problem is worse.OSB rots (and burns) quite easily. EPS foam will adsorpt and never desorpt (think sinking dock floats made of EPS) Google Juneau SIPs disaster for one example of what can happen

Guest;

EPS will absorb water if it is in or under water, however it will also drain out at the same rate it was absorbed once it is taken out of water

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXX-4K8SBYX-1&_user=10&_coverDate=08/31/2006&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1588479103&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6794b2aefd98a3d9126ac384c06451ce&searchtype=a Sip Supply (no conflict of interest suggested byu your name I am sure) Is you statement based on your own scientific analysis in your wifes kitchen or a real scientific analysis Ever wonder why float logs eventually get saturated and sink. You can put them out in the desert nd they will always be waterlogged once they take on water at the rate of 2-6% The osmotic pressure of vapour transmission can exceed the "pressure" of just dipping a piece into water by the way. If something only takes on at the rate of 2% what do you suppose the accumulation is over --say 20 years- if it cannot desorp

Wow that is the mother of all URLs. You can use the site tinyurl.com to post a much smaller one (I promise no one will make fun of you for having a tiny URL).

I don't see how this article backs up your point or relates to the proper use of SIPs. My experience is that waterlogged wood does dry out if given the opportunity which seem unrelated to the article. Juneau was a case of very poor construction in essentially a temperate rain forest. There are very few places that get significantly more rainfall than Juneau, AL. Also I don't know of any normal house construction that endures submersion in water for 28 days. It reminds me of New Orleans but I'm not sure that was even 28 days. Any construction should have proper rain screening, drainage and proper paths for assemblies to dry out (see Buildingscience.com for how this varies by climate).

obvious I was not referring to wood--the issues with that are well documented. The ES will accept and hold water from the vapour transmission through it--or attempt for same. It will not , however, give that moisture back up. There is no real reason to be concerned about the wood becoming saturated as it does desorb fairly well if given a chance. It will rot first anyway. As to the url, how about you just google key words related to the subject and study the issue for yourself. Anything someone with a divergent opinion would say is not allowed anyway by ll of the regular academics here. Don't listen to me, study for yourself.

Posted By guest on 24 Dec 2010 09:32 PM
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXX-4K8SBYX-1&_user=10&_coverDate=08/31/2006&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1588479103&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6794b2aefd98a3d9126ac384c06451ce&searchtype=a Sip Supply (no conflict of interest suggested byu your name I am sure) Is you statement based on your own scientific analysis in your wifes kitchen or a real scientific analysis Ever wonder why float logs eventually get saturated and sink. You can put them out in the desert nd they will always be waterlogged once they take on water at the rate of 2-6% The osmotic pressure of vapour transmission can exceed the "pressure" of just dipping a piece into water by the way. If something only takes on at the rate of 2% what do you suppose the accumulation is over --say 20 years- if it cannot desorp

Its not rocket science! My testing was not done in lithuania , attached is the test report ,

Guest;

the density used in the testing is inferior to what is used in our sips, your post really has no relevance to SIP construction anyway , we are not building floating docks.

Kitchen sink or laboratory....Your sunken log analogy has no merit either,  anyone who has ever worked with pressure treated lumber knows that a treated 2x4 might weigh 25 lbs. when purchased , but in about 2 weeks of sitting in the sun on the deck you just built will quickly become a normal 15% moisture content

Please read Moisture  and EPS >    http://www.epsmolders.org/4-ruling.html

http://www.universalconstructionfoam.com/products/polystyrene/marine-floatation.php
Sorry to have further confused you by using a term known to those in the field that may be mis-interpreted
I did not mean a "log" of tree origin. I meant an EPS element made for a dock float that most jurisdictions are getting around to banning the use of unless they are fully encapsulated.
EPS will adsorb but not desorb and will eventually sink. When used as the core of a sips panel the vapor transmission will go into the EPS but will not go out of the EPS.
It takes decades for that to be a noticeable problem.
As I work in several different countries and several different environments it is hard for me to accept your analogy about the wood will always return to 15% moisture content. I am sure it does where you are as that is at or close to the mean average relative humidity.
I areas where the average is more like 5% I can assure you the wood dries more and in areas of the world where the average is 80% the wood will normalize at a higher level

Posted By guest on 31 Dec 2010 08:37 PM
http://www.universalconstructionfoam.com/products/polystyrene/marine-floatation.php
Sorry to have further confused you by using a term known to those in the field that may be mis-interpreted
I did not mean a "log" of tree origin. I meant an EPS element made for a dock float that most jurisdictions are getting around to banning the use of unless they are fully encapsulated.
EPS will adsorb but not desorb and will eventually sink. When used as the core of a sips panel the vapor transmission will go into the EPS but will not go out of the EPS.
It takes decades for that to be a noticeable problem.
As I work in several different countries and several different environments it is hard for me to accept your analogy about the wood will always return to 15% moisture content. I am sure it does where you are as that is at or close to the mean average relative humidity.
I areas where the average is more like 5% I can assure you the wood dries more and in areas of the world where the average is 80% the wood will normalize at a higher level

I live in a tropical climate, Since we are not generally using SIPS for flotation devices ........what is the revelance of your post?


"using a term in the field"    ....what is your field anyway?