On Wed, 13 Aug 2014 11:42:02 -0400, I wrote:

and a nonmetallic thermal break to minimize
conduction of outside temperatures as part of the ductwork.

I was starting to research Thermador's suggestion of a nonmetallic thermal
break. Like what to call it so I can buy such an item. And I found someone
has asked the same question I'm asking:

http://www.diychatroom.com/f47/range...climate-90906/

Don. www.donwiss.com (e-mail link at home page bottom).
Don. www.donwiss.com (e-mail link at home page bottom).