COMcheck vs. ASHRAE 90.1 Appendix G: Which Compliance Path Fits Your Project?

Prescriptive compliance with COMcheck

COMcheck demonstrates that each building component — envelope, lighting, mechanical systems — meets the code's prescriptive requirements. It is fast and inexpensive, and works well for simple buildings and tenant fit-outs that meet each requirement individually.

The limitation: if one component falls short, such as higher glazing area, there is little room to trade it off against better performance elsewhere.

Performance compliance with Appendix G

An ASHRAE 90.1 Appendix G model simulates the whole proposed building and compares it with a code-defined baseline. Designers can trade envelope, lighting and HVAC performance against each other, as long as the overall result meets the target.

Appendix G is also the basis for most LEED energy performance credits, so projects pursuing certification usually need it anyway.

How to choose

Choose COMcheck when the design comfortably meets prescriptive limits and no certification is targeted. Choose Appendix G, the basis of our energy modeling and code compliance work, when the design has high glazing or unusual systems, when LEED or other certification is required, or when the team wants to compare HVAC options on energy cost.

Save time on model preparation

Much of an energy model's cost is geometry and zoning setup. Exporting clean rooms and spaces from Revit — with gaps, overlaps and slab thicknesses corrected first — avoids rebuilding the building by hand in the energy modeling software.