How bad would the energy hit be with double steel walls set 3" apart with the exterior of the outer wall covered with 2" of closed cell polyurethane and the 10" space between the double rows filled with cellulose for an area like Auburn, Alabama (zip code 36830)?

Would the 2" of closed cell polyurethane on the exterior be enough insulation to prevent condensation on the steel inside the wall.  If not, then would the cellulose hold the moisture safely until the vapor escapes from the wall. 

Wall from outside in:

Synthetic acrylic stucco
2" of closed cell polyurethane  (please disregard the environmental hit with the polyurethane.  Tight budgets may require 2" of EPS instead.)
3.5" steel stud  (please disregard mechanical fasteners such as screws attaching the exterior insulation)
10" of cellulose held in place with netting
3.5" steel stud
0.5" drywall covered with acrylic paint

Each steel stud wall to have its own separate bottom and top steel channels = no steel contact between the two walls.

The reason I am considering this system is that it is available in my area and the price appears reasonable.  I do not think this system has been built here yet.

I don't think a double stud steel wall would be much different than a double stud lumber wall, there is a software called THERM it's free and you can model this stuff in comparison with other arrangements and see what you get

Posted By Alton on 14 Feb 2014 10:33 PM
How bad would the energy hit be with double steel walls set 3" apart with the exterior of the outer wall covered with 2" of closed cell polyurethane and the 10" space between the double rows filled with cellulose for an area like Auburn, Alabama (zip code 36830)?

Would the 2" of closed cell polyurethane on the exterior be enough insulation to prevent condensation on the steel inside the wall.  If not, then would the cellulose hold the moisture safely until the vapor escapes from the wall. 

Wall from outside in:

Synthetic acrylic stucco
2" of closed cell polyurethane  (please disregard the environmental hit with the polyurethane.  Tight budgets may require 2" of EPS instead.)
3.5" steel stud  (please disregard mechanical fasteners such as screws attaching the exterior insulation)
10" of cellulose held in place with netting
3.5" steel stud
0.5" drywall covered with acrylic paint

Each steel stud wall to have its own separate bottom and top steel channels = no steel contact between the two walls.

The reason I am considering this system is that it is available in my area and the price appears reasonable.  I do not think this system has been built here yet.

Alton,

The 2" of polyurethane will give you ~R6/inch (aged R value) or R12 total not considering the fasteners penetrating the insulation.

The outer 3.5" steel stud wall filled with R13 cavity insulation (cellulose) will give you ~R6 total effective R value (see link below for basis).

The middle 3" cellulose cavity between the steel stud walls will give you ~R11 assuming R3.7 per inch.

The inner 3.5" steel stud wall filled with R13 cavity insulation (cellulose) will give you ~R6 total effective R value (see link below for basis).

Add another R0.5 for the interior drywall.

Total wall R value = 12 + 6 + 11 + 6 + 0.5 = 35.5

http://www.taitem.com/wp-content/up...v-2008.pdf

I'll let someone else address the moisture issue.

http://windows.lbl.gov/software/therm/demo/SteelStudWall/SteelStudWallSWF/SteelStudWallSWF.html this is what I have been tinkering with check it out this tutorial is for steel studs