Re: [papercreters] Re: Insulation Value

MD has a bit of the same issue with vapor drive in the pu foam.  It's a hot topic on the bb and at the workshops.  I've been out of the loop for a while, so don't know if they've dome up with a decent solution.

 

ElfN

 

----- Original Message -----

From: Janoahsh

Urethane insulation is particularly problematic in Arctic or sub Arctic climates for the reasons you describe.  Many houses were built using urethane foam in the Fairbanks Alaska area during the Pipeline Boom during the 70's.  Most of them were torn down because the temperature differential was too great, inside temps in the 70 degree range and outside temps in the -70 degree range in the extreme.  These houses were sealed up so well that moisture built up in the walls and condensed in the foam near the outside surface turning to ice and gradually completely saturated till most insulation value was eliminated.  To make it worse the trapped moisture began rotting the adjacent wood framing material.

This is not as much of an issue here in Homer Alaska due to much warmer low end temperatures, but still this can be a problem as it occasionally gets below zero degrees during cold snaps.  It has been several years but temps used to get down to -20 to -30 F.   I don't like urethane for other reasons like out gassing toxicity, fire, and cost.

Considering the double envelope FC scenario with 12" of papercrete between I am concerned about accumulating water vapor inside the shells and would like input on how to dry it out.  The fact that the structure will be buried except for windows and doors will help to moderate temperature differentials, but I still question the possible long term build up.  Properly mixed FC mortar is water proof, but not completely vapor proof.  As a precaution I'm considering perforated pipe imbedded in the papercrete that can be unplugged and forced dry air circulated through the pipes to dry the insulation.  Does anyone have input on this, like spacing of the pipes and possibly a simple way of drying the air forced through the pipes?  Does this seem like a viable solution?

Janosh

__._,_.___

Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe

__,_._,___