90.1 2010 questions on district steam

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Two questions on how ASHRAE 90.1 2010 considers district (?purchased?)
steam, for both ECB and Appendix G, for NON-LEED projects (e.g. code
compliance using ECB) ? so one can?t rely on supplementary LEED guidance on
DES (i.e. ?Treatment of District or Campus Thermal Energy in LEED V2 and
LEED 2009 ? Design & Construction?).

?[?] Appendix G?s direction for projects using purchased [?] heating is
intended to remove the impact of [?] heating *source equipment*
efficiencies from the building performance rating by using the same
purchased energy rates in the baseline and proposed designs.?

*taken from:*

Energy Standard for Buildings Except Low-Rise Residential Buildings Date
Approved: January 28, 2017*

So ECB & Appendix G 2010 do not recognize 'source' (e.g. central plant)
equipment efficiencies (fair enough, not a building asset). Energy savings
can stem though from baseline HVAC system selection, control parameters,
and secondary equipment efficiencies such as building-side hot water pumps.
Up to now, everything's clear.

Question 1: Shall the primary steam-to-water heat exchanger - the interface
between a publicly- or privately-owned/operated district heating (steam)
system and the building (hot water distribution) ? be considered part of
the *source* (therefore ?neutral?, i.e. no credits or penalties should be
accounted for) or part of the *building* asset (hence a potential source of
recognized energy savings depending on e.g. exchanger selection)? In most
cases, the heat exchanger is actually a building asset, owned and operated
by the building owner. And as there are industry claims of heat exchange
improvements of around 10% depending on exchanger selection and ?steam
conditioning? technology, it?s understandably a fair question for cold
climate locations.

Question 2: If the answer to Question 1 is that the primary steam-to-water
exchanger, and associated technologies, may be considered part of the
'building' (and therefore a potential source of recognized energy savings),
then it raises the question what would be the baseline heat exchange
coefficient or efficiency? Without the latter, it?s hard to take into
consideration steam-to-water conversion improvements.

Past forum discussions have mainly dealt with LEED buildings (which has its
own non-90.1 way of doing things), or on modeling solutions (e.g. setting
up a STEAM-METER in DOE-2.2). But I can?t find clear guidance to answering
Questions 1 & 2.


? Denis?

Denis Bourgeois PhD | denis at rd2.ca

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