I'm working on a LEED project where we are considering an air-source heat pump domestic hot water plant with gas boiler backup for low temperatures where the heat pump capacity drops off. Appendix G of ASHRAE 90.1 does not seem to give guidance as to what baseline should be used (gas or electric resistance) for such a hybrid system. Has anyone encountered this before?

Thanks in advance for any suggestions!

Kind regards,

Molly

Molly Curtz PE BEMP LEED AP BD+C
Senior Mechanical Engineer

Arup
719 Second Avenue Suite 400 Seattle WA 98104
t +1 206 749 9674 d +1 206 493 2234
f +1 206 749 0665
www.arup.com

____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses