[Greenbuilding] Insulation Problems

[Thomas Lewis]

providing a drained airspace behind the cladding would have been a very good thing for your house, but the metal cladding
should eliminate most problems by stopping exterior vapor drive, as
long as the flashing is exceptional you shouldn't have a problem.  

be sure to provide fresh air through a HRV and to keep interior humidity down.

-Tom


"Time makes more converts than reason."  Thomas Paine, Common Sense

--- On Tue, 11/9/10, J Messerschmidt <John at fourpointscg.com> wrote:

From: J Messerschmidt <John at fourpointscg.com>
Subject: [Greenbuilding] Insulation Problems
To: "Greenbuilding" <greenbuilding at lists.bioenergylists.org>
Date: Tuesday, November 9, 2010, 3:08 PM

Hi Listers,
I have a 2 story house under construction, framed and sheathed, with no windows yet in Queens, NY.  It's a renovation only by DoB standards.  Some of the foundation is still there, otherwise it's new construction.  Don't tell anybody.  No thought had been given to green building or building science until now.  The outside has been insulated with 2" Dow styrofoam, but every 24" going up the wall is a horizontal z clip, attached to the sheathing, where the bronze panel cladding will be attached.  Is that a clear description?  So the profile from the inside out is 2x6 wood studs, 3/4" plywood, some kind of rubber painted onto the plywood that could serve as a vapor/air barrier, and 2" styrofoam, cut every 2 feet going up the walls, with z clips in between, and then the bronze siding.

Can't take any of that off and start again, so I'm figuring the space between the styrofoam and the rubber, as well as the space between the styrofoam and the panels would have to serve as the drainage plane. Question 1: Can I count this r-10 styrofoam as part of the whole wall r-value?

Question 2: For the inside, we are thinking of spraying open cell foam in the wall cavities to prevent air flow and increase the r-value.  If we installed 1" rigid with no foil, behind the sheetrock, I think this would block conductive heat loss and would not add another vapor barrier.  Do you think this would work?


Thanks!



John




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