AFAIK the standard test of R-value is to have two test plates and the material under test is placed between the test plates and the heat flow for a given temp difference is measured.
I know that there are some alternate methods, but not sure of all of the details.
Anyway with the standard test FG bats would not have allow any external air circulation.
However, with the typical FG bat is ceil joist the one side is open to moving air (the better the vent the more the air movement).
Does anyone know of any specific test that have been run showing the effective R-value in that application .
I realize that the effective R-value of the bat is often less calculated due to installation errors (not fluffed and have gaps at the edge of the joist). But I am only interest in the affect allow air to move across the face of the bat.
Edited 5/31/2004 12:56 am ET by Bill Hartmann