ASHRAE Journal - November 2023 - 47

TECHNICAL FEATURE
1. The building envelope complies with Section 5.5, " Prescriptive
Building Envelope Compliance Path " ; or
2. Using Section 5.6, " Building Envelope Trade-Off Option, " the
proposed envelope performance factor shall not exceed the base
envelope performance factor by more than 15% in multifamily,
hotel/motel, and dormitory building area types. For all other
building area types, the limit shall be 7%. For buildings with both
residential and nonresidential occupancies, the limit shall be based
on the area weighted average of the gross conditioned fl oor area. "
This requirement preserves design fl exibility and
minimizes documentation effort while improving longterm
building performance (Figures 1 and 2).
Other ECBM and PRM Changes
PRM Addenda
Addendum db. Clarifi cations for determining base
space conditioning categories.
Addendum h. Clarifi es procedure for area weight BPFs
for mixed-use buildings.
Addendum l. Clarifi es how fenestration is
apportioned in the baseline building.
Addendum aa. Fixes inconsistencies in the SI version
for fan power and italicizes " on-site. "
Addendum aj. Clarifi es that transformers falling
between size ranges in Table 8.4.4 shall use linear
interpolation for baseline effi ciency.
Addendum an. Clarifi es and consolidates
requirements for fan system operation.
Addendum bt. Requires baseline chilled water (CW)
and hot water (HW) pumps to run only when load exists.
Addendum cq. Changes " water-cooled " to " fl uidcooled "
and other minor edits.
Addendum da. Aligns PRM documentation simulation
program requirements with ECB.
Addendum i. Provides exception from baseline energy
recovery requirements for systems serving a laboratory
zone with a total laboratory exhaust volume greater than
15,000 cfm (7079 L/s).
Addendum w. Clarifi es baseline chillers are sized
based on peak coincident load.
Addendum ct. Clarifi es how window to wall ratio
(WWR) is determined; specifi es baseline does not
include automatic shading, removed redundant
reference to roof albedo.
ECBM
Addendum bh. Updates the temperature coeffi cient
of performance (COP) for photovoltaic (PV) baseline
systems for consistency with PV Watts.
Addendum cs. Requires baseline high-capacity gas
boilers to meet increased effi ciency and baseline service
water heating (SWH) equipment to meet prescriptive
requirements.
Addendum k. Eliminates baseline fan power credit
for energy recovery when energy recovery is not in the
baseline design.
Addendum s. Establishes solar refl ectance
requirements for baseline walls.
ECBM and PRM
Addendum be. Updates Standard 140 required testing
for simulation programs.
Addendum bg. Expands applicability to buildings
sites and properties in accordance with the general
expansion of Standard 90.1 scope.
Addendum bu. Informative note recommending the
use of ASHRAE Standard 209.
Addendum v. Clarifi es the documentation (including
the simulation fi le) submitted to the authority having
jurisdiction [AHJ]).
Addendum t. Specifi es requirements for simulating
envelope air leakage in baseline and proposed building.
Addendum ad. Renumbers reference sections for
consistency with changes to other sections.
Addendum av. Specifi es how thermal bridges are
modeled in the baseline and proposed designs.
Summary
Many changes to performance paths, ECBM and
PRM, are based on feedback from the modeling and
compliance communities. We will continue to balance
the needs of different groups in future changes to these
performance paths. If you would like to be involved
in the process of future updates, consider attending
Energy Cost Budget subcommittee meetings. Many
thanks to the ECB subcommittee, SSPC 90.1 and
ASHRAE staff.
References
1. Thornton, B.A., G.P. Sullivan, M.I. Rosenberg, M.C. Baechler.
2015. " Preserving Envelope Effi ciency in Performance Based Code
Compliance. " PNNL-24359. Pacifi c Northwest National Laboratory
for the United States Department of Energy.
2. Jonlin, D., B. Thornton, M. Rosenberg. 2016. " Can HighPerformance
Equipment Lead to a Low-Performance Building? "
ACEEE Summer Study on Energy Effi ciency in Buildings.
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ASHRAE Journal - November 2023

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