The U-factors for typical construction assemblies are included in Chapter 3 and Appendix CA. These values shall be used for all calculations. Where proposed construction assemblies are not represented in Chapter 3 or Appendix CA, values shall be calculated in accordance with the ASHRAE Handbook of Fundamentals, using the framing factors listed in Appendix CA.
For envelope assemblies containing metal framing, the U-factor shall be determined by one of the following methods:
- Results of laboratory measurements according to acceptable methods of test.
- ASHRAE Handbook of Fundamentals where the metal framing is bonded on one or both sides to a metal skin or covering.
- The zone method as provided in ASHRAE Handbook of Fundamentals.
Effective framing/cavity R-values as provided in Appendix CA. When return air ceiling plenums are employed, the roof/ceiling assembly shall:
- 4.1. For thermal transmittance purposes, not include the ceiling proper nor the plenum space as part of the assembly; and
- 4.2. For gross area purposes, be based upon the interior face of the upper plenum surface.
- Tables in ASHRAE 90.1 Normative Appendix A.
- Calculation method for steel-framed walls in accordance with Section C402.1.4.1 and Table C402.1.4.1.