Panels rate at R-17 (4.5”), R-25 (6.5”), R-31 (8.25”), and R-39(10.25”). In addition, because SIP panels are so much more airtight and have thermal mass properties, they have been known to outperform these fiberglass ratings by up to 50%. A recent study by Oak Ridge National Laboratories in Oak Ridge, TN, shows a 4 ½” SIP wall outperforming 2×6 stud framing with fiberglass insulation. Learn more about SIP R-Value properties.