Fleming Energy Efficient Fact Sheet

What do the R and U value ratings mean?

Most building products manufacturers cite a calculated value for thermal performance (R and U Values) of doors. While this remains the industry standard, more specs with the latest standards for thermal transmittance (ASTM C 1363) and air infiltration (ASTM E283) are being written.  Note, ASTM C1363 is the most cur-rent test standard for thermal transmittance and replaces ASTM C 236.