Replies

1. 
   Mike_Smith | Sep 16, 2001 06:32am | #1

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   the insulated bay....R-value of a 1 inch air space is apx. 1

   insualtion is apx. 3

   also.. the joist bay is big enough so you can get convection currents in it.. so there is no credit for that "dead air" space since it is not "dead"

   the max dimension is 3/4 x 3/4 x 3/4.... after that you start to get measureable air flow across the space...

   the architect must have something else in mind.. though for the life of me i could tell what....

1. 
   Bill_Hartmann | Sep 16, 2001 06:32pm | #2

   *CharlesIs it possible that the attic is conditioned space and that the insulation was going to be on/under the roof?

1. 
   charles_elkins | Sep 16, 2001 09:12pm | #3

   *Bill-- Im not sure about the details, but that probably would make the most sense. I heard about it in a conversation with one of the HVAC guys doing my house. We were talking about air movement in general, and he mentioned it-Im going to try to find out more details the next time they come out.I was hoping to flush out some fact and ideas on the subject-- Mike's awnser sounds right to me though.around here the focus is on cooling, and I imagine RADIATION is the #one enemy, especially on a roof (but I dont know that for sure)

1. 
   Bill_Hartmann | Sep 16, 2001 09:32pm | #4

   *CharlesYou might go to http://www.buildingscience.com and look at some of the papers on conditioning atic space where AC ducts are run in the atic in the SW.That is not my climit, but it makes sense to me.

2. 
   charles_elkins | Sep 16, 2001 09:32pm | #5

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   Someone told me today about a house being built- The architect spec'd NO insulation in the attic (!)
   It brings to mind a question-Which has more insulative value-- A joist or rafter bay sealed on all sides (OSB or Plywood glued to the top, w/sheetroch glued to bottom) with nothing but dead air inside OR the same details with fiberglass batts installed?