I have read several comments on these posts that say that an air gap between subfloor and insulation causes an R-value loss. For example:
Case #1 - 9.5" floor joists filled up from bottom of joists to depth of 7.5" with cellulose insulation (thus giving an air gap of 2" between top of insulation and bottom of subfloor), R-value = X.
Case #2 - 7.5" floor joists filled up completely to bottom of subfloor with same 7.5" depth insulation (no air gap), R-value = more than X.
(Of course, the cellulose is going to settle after a while, but for the sake of this question, assume no settling)
Maybe there's something I'm overlooking, but I fail to see why the R-value in case #1 would be less than the R-value in case #2.
If someone believes otherwise, would you please comment as to why you think this would be?