Replies

1. 
   DanH | Oct 31, 2008 04:23pm | #1

   Less than 1/3, but how much less depends on a lot of factors. Better to get high-density 3.5" insulation, if you want the added R value.

   Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
2. 
   Piffin | Oct 31, 2008 07:39pm | #2

   shover FG batts R-19 into a 3.5" space and you will be lucky to get R15 instead of typical R13.

   But buy high density R15 made for a 3.5" space and you know you have R15 and don't have to fight with getting the wall board on.

    

    

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