Baseline Service water heating

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Dear E-questers,

I am working on a hospital building project which uses existing heat pump
at site for service water heating.

The issue is arising in modeling baseline hot water system, which as per
ASHRAE 90.1-2013 Table G3.1.1-2 is specified as gas storage water heater
for hospital building type. The gas utility rates will not be available for
the project since no gas heating system is used at site.

I want to confirm whether identical system as proposed case can be
considered in baseline model as the energy cost savings will need to be
compared with existing heat pump at site.

Thanks in advance.

Rushi Quest's picture
Joined: 2019-12-11
Reputation: 0

Hi Rushi,

The exception to Table G3.1.11.j (Baseline) states that you should use propane at the fuel source in the baseline when natural gas is not available at your site. In that case, it?s up to you to find a price for propane in your area or use EIA?s propane prices website like

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ChapinAN's picture
Joined: 2019-01-19
Reputation: 0

I agree with the guidance/discussion so far (the Standard is relatively clear in prescribing natural gas, or possibly propane if your AHJ/rating-authority accepts), but I?m left a little unsatiated? Can we take a step back and discuss the Standard a little further?

What could be the basis or rationale for 90.1 deciding to diverge from ?baseline should match the existing system, as applicable?? Prescribing a service water heating system on the basis of building occupancy certainly adds extra nuance/complexity, and demonstrably can result in existing/real service hot water baseline systems being represented with potentially unrealistic system/fuel types.

I trust the 90.1 committee made this change with deliberation, and fully expect I am missing some part of the bigger picture, but would like to be educated if anyone has a sense of why we?re moving in this particular direction.



For mutual reference, In 90.1-2010 Table G3.1 reads as follows:
[cid:image002.png at 01D6869E.F908B320]
With 90.1-2013, the same passage (highlighted) was revised as follows:
[cid:image005.png at 01D6869E.48012E40]
[cid:image007.png at 01D6869E.48012E40]
And here is the referenced table:
[cid:image008.png at 01D686A1.9B174B20]

[cid:image006.jpg at 01D68773.5A941010]
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[cid:image003.png at 01D6869B.3CE5BBF0]

Nicholas Caton2's picture
Joined: 2019-03-25
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