COMcheck does account for thermal bridging of framing members, furring, etc. (depending upon the assembly). U-factor assembly calculations are taken from ASHRAE Appendix A and ASHRAE Fundamentals. The methodology used to calculate compliance is taken from ASHRAE Appendix C. When an assembly is chosen from the drop down lists in the program, there is a U-factor automatically displayed for that assembly (excluding fenestration). Once the user enters the proposed insulation R-value(s) for the assembly, the program recalculates the assembly and updates the U-factor to the overall U-factor for the entire assembly. Also users have the option to choose "other" as the assembly type. If “other” is selected, the user will then need to enter the overall calculated U-factor for the entire assembly and document those calculations to the building official.