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NC-v4 EAp2:Minimum energy performance

Baseline HVAC System Type

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? 
 

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Marcus Sheffer
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7group / Energy Opportunities
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Wed, 05/19/2021 - 21:17

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.

Wed, 05/19/2021 - 21:41

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?
Profile picture for user sheffer
Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Thu, 05/20/2021 - 14:10

The district systems guidance in the Reference Guide should help answer your question.

Thu, 05/20/2021 - 15:09

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.

Thu, 06/03/2021 - 14:45

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.  

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