Long time listener, first time caller. I have a gray area in what system I should be using for my baseline and wanted to poll the general consensus. I have a building addition where my proposed system is electric heat pumps with supplemental heat from a natural gas boiler for when it is real cold / peak heating load. My first thought is that it should be a fossil / hybrid system (Sys 5). However this boiler that I am using as a backup is the primary heat for the existing building, and is across the LEED boundary. If I use option 1 of the district heating guidelines it says I should treat this heat from the boiler as purchased heat. If I do that do I need to change my baseline system to electric only heat? Thanks.
Brendan Hall, M.Sc., LEED AP BD+C
Brendan,
Based on building type, it sounds like you've determined that your
LEED/Appendix G baseline system is either System 5 or 6.
If the proposed system is designed with a boiler loop connected only for
"backup" - primary system failure, maintenance, or future expansion -
then Electric and Other - System 6.
If the proposed system is designed with a boiler to meet peak heating
loads beyond the capacity of the heat pumps, then you have
Fossil/Electric Hybrid or Purchased Heat - System 5.
If System 5, AND if you believe your boiler system is a District or
Campus Energy System (DES) per the "Treatment of District or Campus
Thermal Energy..." document, AND if you use Option 1 per said document,
AND if you have District Heating only per Table 3, then no changes are
required to the Appendix G baseline system - System 5.
Regards,
Bill