The project consists of non residential building of 6 stories. The proposed design consisted of the first floor (retail spaces) being served by water source heat pumps with the primary heating source being the electrically driven refrigerant compressor in heat pump mode, in the event of severe cold weather the heat rejection loop is equipped with a natural gas fired boiler to supplement the electric heat pump. The remaining floors (office space) utilizes a central, hydronic chilled water cooling air handling unit per floor serving parallel fan powered terminal units with electric heat. It is the design team contention that the heating source for this building is electric and therefore the baseline HVAC system should be a system type 8 per ASHRAE standard 90.1-2007 table G3.1.1A,B since the gas fired boiler only serves as supplementary heat for the first floor water source heat pumps and the primary heat source for the rest of the building is electric heat. If this contention is incorrect then we are not sure of the meaning of "Electric and Others" in the last column of ASHRAE standard 90.1-2007 table G3.1.1A. Please help if you can. Thanks.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
January 24, 2014 - 10:13 am
Sounds like the office portion is a system 6 or 8. The retail could be a system 3. Having the gas boiler on the loop makes this a hybrid system which comes under the fossil fuel column in Table G3.1.1A. You must apply all applicable exceptions under G3.1.1. So perhaps exception a or maybe exception b may apply.