ASHRAE Journal - June 2024 - 36

FEATURE
FIGURE 2 Standard 240P quantification of life cycle greenhouse gas emissions.
Embodied Impact
Product Stage
(A1- A3)
Construction
Stage (A4 - A5)
Use Stage
(B1- B7)
End of Life Stage
(C1- C4)
Circular Economy
Beyond the Building
Life-Cycle Stage (D)
Benefits and Loads
Operational Impact
Cradle to Gate
B6: Operational Energy
B7: Operational Water
Cradle to Grave (Building Life-Cycle Information)
Cradle to Cradle (Building Assessment Information)
Appendices
Normative Appendices are part of the enforceable
portion of the standard. Standard 228's Normative
Appendices consist of a reference appendix
and Compliance Forms, which are to be used to
demonstrate compliance with the standard. Several
Informative Appendices are also provided for
informational purposes only, including an overview
of embodied carbon.
How This Standard Differs From 240P
ASHRAE Standards 228 and 240P both address the
carbon associated with a building, but they have very
different scopes. While the current edition of Standard
228-2023 quantifies only operational emissions
(namely B1, B2 and B6 in Figure 2), ASHRAE/ICC
Standard 240P, Evaluating Greenhouse Gas (GHG) and
Carbon Emissions in Building Design, Construction and
Operation, gives a methodology to quantify the GHG
emissions associated with a building over its entire
life cycle including both embodied and operational
carbon (Figure 2). Operational carbon is the total
GHG emissions associated with the operation of a
building during its use stage. Embodied carbon is the
emissions associated with the extraction, production,
transportation, construction and assembly of building
materials, appliances and equipment. Embodied
carbon could also be described as the carbon footprint
of a building before it becomes operational and may
also include the emissions to maintain and eventually
demolish it. For example, Standard 240P considers
the flooring used in a building, requiring life-cycle
36
ASHRAE JOURNAL ashrae.org J U N E 2024
assessment (LCA) to account for the
embodied carbon of the material.
Over the past several years, ASHRAE
has developed or revised multiple
standards to incorporate GHG metrics
for measuring the carbon emissions of
the built environment to contribute to
slowing its effect on the climate. Both
Standard 100-2024 (discussed below)
and Standard 240P include a specific
set of GHG metrics, as does Section 7 of
Standard 228. Since there is currently no
coordinating standard for GHG metrics
(Standard 242P, Standard Method for
Calculation of Building Operational Greenhouse
Gas Emissions, has recently been initiated
for this purpose), there is divergence between how
each of Standard 100, Standard 228 and Standard
240P treats technical issues such as off-site renewable
procurement qualifications and the disposition of
renewable energy credits (RECs).
The most notable differences between Standard
240P and Standard 228 concern how they treat GWP
time horizons (defaults to 20 years in Standard 240P
and defaults to 100 years in Standard 228-2023)
and whether they account for off-site renewable
procurement (not addressed in Standard 240P; fully
addressed in Standard 228).
How Does Standard 228 Relate To Standard 100?
ANSI/ASHRAE/IES Standard 100-2024, Energy and
Emissions Building Performance Standard for Existing Buildings,
has targets for energy and emissions performance,
organized by building type and climate zone that
are derived from the Commercial Buildings Energy
Consumption Survey (CBECS) and Residential Energy
Consumption Survey (RECS) data. Buildings meet
Standard 100-2024 by being below energy use intensity
(EUI) and greenhouse gas intensity (GHGI) targets
that are the 25th percentile of the EUI and carbon
distributions for the building type and climate zone.
Buildings that do not meet the target can qualify by
performing an ASHRAE Level 2 energy audit with
decarbonization assessment and implementing costeffective
measures. Authorities having jurisdiction
(AHJs) adopting Standard 100 are able to modify the
target percentile for their jurisdiction. Unlike Standard
A1: Raw Materials Supply
Total Life-Cycle Impact
A2: Transport
A3: Manufacturing
A4: Transport
A5: Construction and
Installation Process
B1: Use
B2: Maintenance
B3: Repair
B4: Replacement
B5: Refurbishment
C1: Deconstruction/Demolition
C2: Transport
C3: Waste Processing
D4: Disposal
Reuse
Recovery
Recycling Potenrial
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ASHRAE Journal - June 2024

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