Why does the R-value for Hy-Fi change with the different foam insulation?

The R-value for a reflective air space depends on the temperature difference across that air space.  The temperature across the air space depends on the r-values in the system since the bounding temperatures are fixed.

Product Reference: 

HY-Fi

Professionals Reference: 

Builder
Insulation Contractor
Rater
Remodeler

Product Applications Reference: 

Walls
Walls
Walls
Walls
Walls

Building Type Reference: 

Wood Framed

The Company We Keep

NAHB logo
ICAA logo
RIMA-I
International Association of Plumbing and Mechanical Officials
Spray Polyurethane Form Alliance
Florida Green Building Coalition
South Face