I have never heard of Div 23 or 26. HVAC Commissioning for us is a 57 checklist that makes sure the installer goes over every temperature, every pressure, air flow measurements, etc to make sure that the unit installed is getting the efficiency that was paid for. A study by Texas A & M shows that 90% of all AC’s installed are incorrectly charged when installed, so the units do not run efficiently. We make sure what is paid for, is what they get.