[Greenbuilding] thermal bridging?

[Alan Abrams]

> I have built double walls like this: 2x4 framing, filled with  
> insulation, then covered inside with 1/2" foil faced foam, which is
> then strapped with 2x4's flat. All the wiring takes place in this 1.5"  
> space, using 4"x4"x1.5" boxes. Taping the foam joints will make it a  
> vapor barrier. Drywall goes up vertically, good if your ceiling is over  
> 8'. Finished wall is the same thickness as  2x6 construction. For  
> headers, I replaced the foam with 1/2" plywood, glued and nailed to  
> make a hollow (w/insulation)
> box beam. For a really well insulated house, I would frame with 2x6's @  
> 2' oc.


This makes extra good sense in a mixed humid climate--assuming some
insulation for the inner cavity--as the vapor is then insulated on both
sides--so it should never hit dew point, whether cooling or heating.


-AA