[Greenbuilding] Vapor barrier outside of wide cavity dense pack cellulose walls.

conservation architect elitalking at rockbridge.net
Sat Nov 1 11:02:58 CDT 2014


http://www.greenbuildingadvisor.com/blogs/dept/musings/dense-packed-cellulose-and-wrong-side-vapor-barrier
Here is an interesting blog about thick cavity framed walls filled with dense pack cellulose and covered on exterior with ice shield vapor barrier.  This is in a cold climate.  The video link in the article shows the owner making the readings that showed low moisture content on interior side of exterior sheathing.  My hunch is that he did such a good job of making the assembly air tight, which the ice shield is part of that not much air is reaching the exterior sheathing, therefore less moisture.  However, I suspect this assembly is more vulnerable to less perfect installations.  
Another issue they discuss is the hydroscopic quality of cellulose to absorb moisture and distribute evenly.  I am curious about the vapor permeable foams that are air tight (eps, open cell foam).  Do they have the ability to redistribute vapor?  Does vapor that condenses in a vapor permeable foam able to evaporate again to continue upward migration out of the system.  I would expect that the upward buoyancy of vapor makes the bigger threat at top if there is a vapor barrier.  I am an advocate for air tight, vapor permeable foams with ventilation above to allow continued migration of vapor out of the system.  
Hoping for your thoughts.  
Eli  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20141101/39b91d63/attachment.html>


More information about the Greenbuilding mailing list