One of the more noteworthy characteristics of Foard Panel SIPs is how well they perform thermally. The tables below compare SIPs with their most common competitor; stick construction with fiberglass (or any batt) insulation.
In order to appreciate these tables, however, the concepts of “Center of Cavity” and “Whole Wall” R-values need to be understood. Center of Cavity refers to the R-value of the insulation only. Whole Wall, as the term implies, takes into consideration the thermal properties of all the components of a finished wall system.
Naturally, Whole Wall R-values are lower than Center of Cavity R-values. Conventionally framed, fiberglass, systems typically perform at only 65% of the stated Center of Cavity R-value. Once thermal bridging, convection within the bay and air infiltration are taken into account, an R-19 (center of cavity) wall, for example, will perform at only R-13 (whole wall). Here is the good news! Foard Panel SIPs perform at 96% of the stated Center of Cavity R-value. This is because the SIPs that form the building envelope are super-tight. They don’t experience air infiltration, thermal bridging, or bay convection. Because Whole Wall performance for these two methods of insulating are so different, it has been difficult for many people to make accurate comparisons and to choose appropriate SIPs for their projects. These tables were designed to help with that process.
|Wall Thickness||Fiberglass||Cellulose||EPS SIP||NEO SIP||XPS SIP||PIR SIP|
|4.5"||Center of Cavity||R-11||R-13||R-15||R-18||R-19||R-23|
|6.5"||Center of Cavity||R-17||R-20||R-23||R-26||R-29||R-34|
|8.25"||Center of Cavity||R-23||R-26||R-29||R-36||R-37||R-44|
|10.25"||Center of Cavity||R-29||R-33||R-37||R-45||R-47||R-56|
|12.25"||Center of Cavity||R-35||R-40||R-45||R-54||R-57||R-67|