how much difference in price and quality between R19 and R20 per square feet ??- P+ z0 H- h% n. ^' _1 A2 x4 g6 p
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who can explain why use R30 for attic. 8 J. ]- S+ t. j" c, e
1#KochFord . O# B5 O6 H) v& h; @& YThe higher R value, The better insulation performance.. v7 i1 p4 B6 s( B' C
In winter, the hot air always floats up due to thermal buoyancy, so R value for the roof is normally higher than that for exterior wall.2 T/ S* o9 u- [8 ^+ N2 b7 u
Hope my answer helps.