Hi,
If the proposed building has central heating and cooling systems consisting of heatpumps and chillers as the main sources of heat/chilled water in addition to purchased heat/chilled water used as topup heating/cooling how should the baseline building be modelled?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
May 19, 2021 - 5:17 pm
See 90.1-2010 Setion G3.1.1. It depends on whether the project is residential or not, how many floors and its conditioned area.
Samer Hassanie
Energy Consultant1 thumbs up
May 19, 2021 - 5:41 pm
Thank you Marcus for the fast reply. But I am more concerned about the energy sources in the baseline building.
Should the baseline be modelled with onsite energy production only or should the purchased heat/chilled water be taken into account in some way?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
May 20, 2021 - 10:10 am
The district systems guidance in the Reference Guide should help answer your question.
Samer Hassanie
Energy Consultant1 thumbs up
May 20, 2021 - 11:09 am
Thank you, I am also aware of the guide but there is nothing in it or in ASHRAE 90.1 about mixed on-site energy production and district energy systems. The only hybrid system mentioned is fossil/electric but not purchased/electric for example.
Moreover, mixing those two systems is not a trivial matter. The baseline on-site energy production systems follow design supply and return hot/chilled water temperatures according to ASHRAE std. 90.1 2010 (G3.1.1.3, G3.1.1.4, G3.1.1.8 and G3.1.3.9), whereas if one was to model the DES according to Option 1 Path 1 of the guide then the design supply and return hot/chilled water temperatures have to be exactly as in the proposed building design.
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
June 3, 2021 - 10:45 am
The Baseline Case model should be modeled using the same ratio (percentage) of purchased versus on-site energy as the Proposed Case. In this case I would model all loop temperatures according to Appendix G values.