ASHRAE Journal - June 2024 - 34

FEATURE
than 24 months;
y Existing zero net energy and zero net
carbon buildings and their sites-buildings
or portions that have been occupied in their
most recent occupancy class for at least 24
months; and
y Zero net energy and zero net carbon
FIGURE 1 Energy flows across the boundary.
Imported Nonrenewable Energy, Einren
Imported Specific Off-Site Energy, Eispec
Imported Transportation Vehicle Energy, Eiv
Imported Landscaping Energy, EiL
Imported Energy
portfolio and community-a collection of sites
wholly owned or leased by a single entity
(portfolio) or a community of sites within a
jurisdictional boundary (community).
In all cases compliance is awarded by the
authority having jurisdiction (AHJ) if the forms provided
within Standard 228, having been completed and
verified by qualified personnel, meet the requirements
of each category.
Energy Flows Across the Boundary
Underpinning all calculations of energy and emissions
associated with an applicant site is the energy flow
across the boundary (Figure 1). The boundary is the
location at which positive and negative energy flows
are measured to determine compliance. Standard 228
organizes energy flowing in and out of the site into three
categories; imported energy, exported energy and other
energy.
Each energy flow is measured and converted to
consistent units, such as kWh. Each then becomes
a term in the site's energy balance equation that
determines whether it qualifies as " zero net energy. "
Layering emission factors onto the equation results in
the site's emission balance that determines if it qualifies
as " zero net carbon " when combined with any off-site
renewable energy or qualified carbon offsets associated
with the site or group of sites.
Source Energy Performance Calculation
Source energy quantities used in the standard's zero
net energy formula are calculated by multiplying the site
energy use (or energy exports from the site) by source
energy conversion factors from Table 1-Table 4 in the
standard. Source factors provided for the United States
are broken down by E-Grid region and for Canada are
broken down by province and territory. Source factors
used outside the boundaries of these two countries are
to be supplied by the authority who is implementing, or
requiring, the standard. In addition, some source factors
34
ASHRAE JOURNAL ashrae.org J U N E 2024
Exported Nonrenewable Energy, Exnren
Exported Renewable Energy, Exren
Exported Transportation Vehicle Energy, Exv
Exported Energy
Other:
Off-Site Renewable Energy, Eoren
On-Site Nonrenewable Energy Used On-Site, Eonren
that may require further policy or local specificity are
to be determined by a " qualified person, " as defined
in ASHRAE standards. The factors for biomass used in
the calculation of hourly electricity generation must be
provided by the authority described above.
Greenhouse Gas Emissions Performance Calculation
Similar to source energy calculations, greenhouse gas
(GHG) emissions quantities used in the standard's zero
net carbon formula are calculated by multiplying the
site energy use (or energy exports from the site) by GHG
conversion factors from Table 5-Table 8 in the standard.
In the main body of the standard, GHG factors were
calculated assuming a global warming potential time
horizon of 100 years (GWP100). GHG factors using a time
horizon of 20 years (GWP20) are compiled in Informative
Appendix E.
Qualifications of Off-Site Renewables
In most use cases, projects will be able to procure
off-site renewables to help meet compliance with
the standard. The requirements for which types of
renewables may be applied to the standard, for how
much of the total compliance obligations can be met
by off-site renewables and for the rate at which offsite
procurement based on its type and age must
be discounted relative to on-site generation are all
included in Section 8 of the standard. That section also
requires that all Renewable Energy Certificates (RECs)
associated with clean energy used for compliance
be retired. Limits are also set on where the off-site
electricity generation can be located relative to the
project's location. Additional information about the use
of off-site renewable energy procurement is provided in
Informative Appendix B.
Site
Energy
Services
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ASHRAE Journal - June 2024

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