We have a mixed use facility that is 34% hotel, 34% office, and 32% parking garage. The office is served by rooftop units with gas heat, the hotel rooms are served by PTACs with electric heat, and the parking garage is unconditioned. Since the three spaces all have completely different functions and are essentially equal in area, we have modeled the baseline system as follows: Office - System 7 – Hot water fossil fuel boiler, Hotel rooms – System 2 – electric heat pump, parking garage – included in the model, but thermostatic set points were set out of range so that the system will never turn on (per LEED requirements). In the hotel portion of the building, there are also several smaller units that serve lobbies, corridors, a laundry room, and a fitness room that have gas heat. We are modeling these as System 3 (fossil fuel furnace) in the baseline. Is it acceptable to have a combination of electric and gas heated systems? We want to save energy by using gas heat, and we wouldn’t want to change these smaller units to electric just to avoid being penalized in the LEED model.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 4, 2014 - 9:32 am
Yes it is acceptable to have mixed fuels in the model as long as the heating fuel source is the same in each distinct area of the models.
I would make the office predominant. Enter Table G3.1.1A using only the area of the office, not the entire building. The hotel then comes under G3.1.1 exception a and the auxiliary spaces in the hotel under exception b perhaps? Is the garage heated or cooled? If not it would have no set points as it is unconditioned space.