[Bldg-sim] LEED ID+C Baseline
Víctor Moreno Solana
gestienergetica at gmail.com
Fri Aug 30 05:22:17 PDT 2024
Hi Chris.
I just developed a similar simulation.
If the LEED project has been registered after March 1, 2024, you must
follow the v4 2024 Update. Projects registered before March 1, 2024 are
subject to the original v4 criteria.
*Envelope:*
- *v4 2024 Update:*
https://www.usgbc.org/credits/IDC/v4/ea403/2024update?return=/credits/Commercial%20Interiors/v4/Energy%20&%20atmosphere.
Comparison against a baseline tenant project that complies with Standard
90.1–2010, Appendix G, with errata but without addenda (or a USGBC-approved
equivalent standard outside the U.S.). Baseline envelope parameters must be
modeled as “New Construction” according to Table G3.1(5) (baseline),
Sections a–e. Alternatively, projects documented with existing conditions
prior to renovation per Table G3.1(5)(baseline) Section f shall demonstrate
an 8% minimum improvement in proposed performance rating compared with the
baseline performance rating.
- *Original v4 criteria:*
https://www.usgbc.org/credits/commercial-interiors-hospitality-commercial-interiors/v4/ea104.
The baseline project envelope must be modeled according to Table G3.1(5)
(baseline), Sections a–e, and not Section f. Document the energy modeling
input assumptions for unregulated loads.
*HVAC:* The following data are exposed on the LEED Reference guide:
Contribution of Base Building HVAC and Service Water-Heating SystemsIn many
projects, a portion of a base building HVAC system serves the project’s
tenant space. To allocate a percentage of that HVAC system to the tenant
area, use whichever of the following two methods is more appropriate.
Method 1 is applicable when the additional spaces served by the HVAC or
service water heating system have similar occupancies to the project space,
provided the resulting unmet load hours for the proposed design do not
exceed the amount allowed by ASHRAE 90.1.
- Determine the total square footage (square meters) served by the HVAC
or service water-heating system.
- Determine the project floor area served by the HVAC or service
water-heating system.
- For air-handling units, determine the design supply airflow, design
fan power, design heating capacity, design cooling capacity, and outdoor
airflow. For central service water heaters or thermal energy plants (e.g.,
steam, hot water, or chilled water) located in the building, determine the
chiller or boiler quantities and capacities, storage tank volumes as
applicable, pump design supply volume for each pump as applicable, heat
rejection fan power, and any other pertinent parameters relative to HVAC
system capacities.
- Determine the relative contribution of the HVAC or service
water-heating system to the project floor space by applying the project
floor space ratio to each design parameter (design supply airflow, design
fan power, design heating capacity, design cooling capacity, outdoor
airflow, chiller capacity, service water heating storage volume, or pump
capacity):
Adjusted parameter = Parameter x Project area served by system / Total area
served by system
- Model the HVAC or service water-heating system based on the actual
design conditions and sequence of operations, but use the adjusted
parameters as calculated above.
Method 2 is applicable when the other spaces served by the air-handling
unit have dissimilar occupancies to the project space.
- For air-handling units, determine the design supply airflow, design
fan power, design heating capacity, design cooling capacity, and outdoor
airflow. For central thermal energy plants or service water heaters located
in the building, determine the chiller or boiler quantities and capacities,
storage tank volumes as applicable, pump design supply volume for each pump
as applicable, heat rejection fan power, and any other pertinent parameters
relative to HVAC system capacities.
- Determine the percentage allocation of HVAC or service water heating
capacity to the project space, using the following equations. % allocation
= Airflow allocated to project space / Total design supply airflow %
allocation = Chilled water capacity allocated to project space / Total
chilled water capacity
- Example: A dedicated outside air system supplies the entire building,
and VAV boxes distribute the outside air to each tenant space. The team
makes the calculation as follows: % allocation = [AHU design supply flow] /
[Sum of all VAV box peak design flows] x [VAV box peak design flow for
project space]
- Provide documentation from the base building’s owner identifying the
airflow and/or thermal capacity allocated to the project space versus the
total design supply airflow and/or thermal capacity. Justify this
percentage allocation in a narrative.
- Identify the different occupancies, by type and square footage (square
meters), served by the air-handling unit or thermal energy system.
- In ASHRAE 90.1 User’s Manual or ASHRAE 62.1, look up default
assumptions for the other occupancies’ lighting loads, ventilation,
occupancy, etc. Use these values to determine (per square foot or square
meter) the peak heating and cooling loads, design supply air volume, and
design outside air volume for the other occupancies:
Total load = Sum [(Design load/ft2) x (Area)]
Adjusted parameter = Parameter x Total project area served by AHU or
thermal system / Total area served by AHU or thermal system
- Model the air-handling unit or thermal energy system based on the
actual design conditions, but use the adjusted parameters as calculated
above.
Central Plant or District Energy SystemsIf the base building is served by a
central thermal energy plant or a district thermal energy system and the
project is following Option 1, the team may demonstrate compliance with EA
Prerequisite Minimum Energy Performance and EA Credit Optimize Energy
Performance by using Path 1, ASHRAE 90.1–2010, Appendix G; Path 2, Full DES
or central plant performance accounting; or Path 3, Streamlined DES
modeling. *Scope of DES equipment inclusion.* Downstream equipment (e.g.,
heat exchangers, steam pressure reduction stations, pumps, valves, pipes,
controls) may not be located in a commercial interiors project, but when
present, all such equipment must be included consistently in the scope of
EA Prerequisite Minimum Energy Performance and EA Credit Optimize Energy
Performance. Upstream equipment is included or excluded depending on the
chosen compliance path. The proposed design for any building air
distribution systems, ground source heat pump loops, or water source heat
pump loops must still be modeled consistent with Method 1 or 2 (see *Further
Explanation, Contribution of Base Building HVAC and Service Water Heating
Systems).
<https://www.usgbc.org/credits/commercial-interiors-hospitality-commercial-interiors/v4/ea104?view=guide#>*
*Energy simulation versus postprocessing.* Whenever possible, incorporate
system and equipment performance parameters directly into the energy
simulation. Potential methods include developing efficiency curves and
scheduling equipment operation and curves. Postprocessing of DES
performance is acceptable if reasonable simulation methods are not
available or are too onerous. All postprocessing methodologies must be
fully documented.Path 1. ASHRAE 90.1–2010, Appendix GModel the proposed and
baseline designs using purchased energy according to ASHRAE 90.1–2010,
Appendix G. The project may be modeled using purchased energy even if the
building’s central plant generates the thermal energy for the project
space. *Energy rates* All virtual DES energy rates must be identical in the
baseline and proposed cases. If tariffs or rates are not available from the
district plant servicing the project, such as campus or military plants, or
for central plants located within the building, calculate the rates based
on the virtual electric and fossil fuel rates from the model. If a flat
rate structure, in which the cost per unit of energy is the same throughout
the year and there are no demand charges, is being used for all energy
sources, then those flat rates become the virtual energy rates for the
project. If all energy rate structures are not flat, a preliminary run of
the baseline case energy model must first be completed to identify the
virtual electric and fossil fuel rates for the project. For this
preliminary run only, the rate for the energy supplied by the DES or
central plant may be left blank or entered as any value. Once all the
virtual energy rates are identified for electricity and fossil fuel,
calculate the virtual DES or central plant rates for both the baseline and
proposed cases, using the values in the minimum energy performance
calculator provided by USGBC. *Energy Rates for Path 1* If tariffs or rates
are not available from the district plant servicing the project (e.g. for
campus or military plants), calculate the rates based on the virtual
electric and fossil fuel rates from the model:
- If a flat rate structure is being used for all energy sources (meaning
the cost per unit energy is the same throughout the year, and there are no
demand charges), then these flat rates simply become the virtual energy
rates for the project.
- Otherwise, if all energy rate structures are not flat, then a
preliminary run of the Option 1 Baseline Case energy model must first be
completed to identify the virtual electric and fossil fuel rates for the
project. For this preliminary run only, the rate for the DES-supplied
energy may be left blank, or may be entered as any value.
- Once all the virtual energy rates are known for electricity and fossil
fuel, the virtual DES rates for both the Baseline and Proposed Case are
then derived as follows: District Chilled Water Rate: Units of $/(Btu x 10
6) = Virtual Electric Rate (in $/kWh) x 71 Units of $/ton-hour = Virtual
Electric Rate (in $/kWh) x 0.85 Units of $/kWh = Virtual Electric Rate (in
$/kWh) x 0.24
District Hot Water Rate: Units of $/(Btu x 106) = Virtual Fuel Rate (in
$/(Btu x 106)) x 1.59 + Virtual Electric Rate (in $/kWh) x 3 Units of
$/kWh = Virtual Fuel Rate (in $/kWh) x 1.59 + Virtual Electric Rate (in
$/kWh) x 0.01 Units of $/therm = Virtual Fuel Rate (in $/therm) x 1.59 +
Virtual Electric Rate (in $/kWh x 0.3)
District Steam Rate: Units of $/ (Btu x 106) = Virtual Fuel Rate (in
$/(Btu x 106)) x 1.81 + Virtual Electric Rate (in $/kWh) x 3 Units of
$/kWh = Virtual Fuel Rate (in $/kWh) x 1.81 + Virtual Electric Rate (in
$/kWh) x 0.01 Units of $/therm = Virtual Fuel Rate (in $/therm) x 1.81 +
Virtual Electric Rate (in $/kWh x 0.3)Exception: to obtain the virtual
fuel rate when the connected building does not use fossil fuel but the DES
central plant does, use a flat rate consistent with the central plant rates
or the historic average local market rates (no preliminary model run is
needed). The virtual fuel rates must match in the Baseline and Proposed
Case. The virtual DES rates are then input into the modeling software for
each DES source and used for the remainder of the process. Alternatively,
the virtual DES rates may be used to calculate the DES energy costs
directly by multiplying the DES energy consumption for each DES source by
its virtual DES rate. All virtual DES energy rates must be identical in the
Baseline and Proposed Case.Path 2. Full DES or central plant performance
accountingPath 2 is available to projects connected to a central plant
or DES that wish to account for average efficiency across a smaller time
step. The energy model scope accounts for both downstream equipment and
upstream equipment and requires calculation of the district energy average
efficiencies using either modeling or monitoring. *Energy rates* All DES
energy rates must be identical in both the baseline and the proposed cases.
Use local rates as they would normally apply to the project for the energy
sources under consideration. For energy sources used by the DES but not
normally available to the building, such as diesel fuel, use the rates
charged to the DES. If this information is not available, use
representative market rates. Exception: For DES plants that operate under
specific and atypical rate structures and actively take advantage of those
rates through strategies such as load management or energy storage, use the
rate structures as they apply to the DES. *Baseline plant* Model the
baseline case with a dedicated plant that is compliant with ASHRAE
90.1–2010, Appendix G, baseline requirements. Model the baseline building
plant with conventional equipment using performance parameters and
efficiencies per ASHRAE 90.1–2010, using energy sources corresponding to
the DES or central plant. *Proposed plant* Model the proposed case with
a virtual central plant or DES-equivalent plant. Model a virtual plant with
the same efficiencies as the entire upstream DES heating, cooling, and
combined heat and power (CHP) system, including all distribution losses and
energy use. Equipment efficiencies, distribution losses, and distribution
pumping energy may be determined using any of the following methods:
- Monitored data
- Engineering analysis
- Default values
Efficiencies and losses may be determined and modeled at any level of
time resolution, from hourly to annual. However, the time resolution must
be sufficiently granular to capture and reasonably represent any
significant time- or load-dependent interactions between systems, such as
thermal storage or CHP. Monitoring data for heating, cooling, pumping, and
cogeneration may be used only if the thermal loads that are monitored
represent at least 90% of the load on the building, campus, or district
plant predicted after occupancy of the project space. Monitoring and
analytical methods may be combined as necessary and appropriate. Whether
using monitoring or an analytical method, the methodologies must be fully
documented. The following specific requirements apply. *Heating and
cooling plants* Efficiencies, whether determined through monitoring or
analytically, must include all operational effects, such as standby,
equipment cycling, partial-load operation, internal pumping, and thermal
losses. *Thermal distribution losses* For central plants located inside
the project building, the thermal losses are assumed to be zero. For
district systems, use monitored data or an engineering analysis.
- If using monitored data, determine the distribution losses for the
DES by measuring the total thermal energy leaving the plant and comparing
it with the total thermal energy used by the buildings connected to the
DES. De-rate the plant efficiency accordingly in the energy model:
Plant efficiency (%) x [100% – distribution loss (%)]
- An engineering analysis takes into consideration all distribution
losses between the DES and the building. For distribution main
losses, use
a prorated amount based on load. For dedicated branch losses,
use the total
losses of the branch that feeds the building, including heat losses and
steam trap losses. Compare the total losses with the total load of the
building to get a percentage distribution loss relative to load and
downgrade the plant’s efficiency accordingly in the energy model.
*Pumping energy* Whether through monitored data or engineering analysis,
determine pumping energy for the project by prorating the total pump energy
of the DES or central plant by the ratio of the annual thermal load of the
project space to the total annual DES thermal load. Model the pump energy
as auxiliary electrical load. Pumping energy must be determined or
estimated where it applies (i.e., there is no default value). *Default
efficiencies and losses* Actual efficiency performance data on the DES
serving the project building are preferred. If the project team cannot
obtain or determine the actual performance data, use the following default
values. These values are conservative and are intended to represent a DES
with relatively low efficiency; a well-designed, well-operated DES
generally performs better.
- DES heating plant: 70% (higher heating value, HHV) for the total
boiler plant average efficiency
- DES cooling plant: coefficient of performance (COP) of 4.4 for the
total cooling plant average efficiency (including cooling towers and
primary pumps)
- Thermal distribution losses, including minor leaks or condensate
losses:
- Chilled water district cooling, 5%
- Hot water district heating, 10%
- Closed-loop steam systems, 15%
- Open-loop steam systems, 25%For steam systems that are partially
open and partially closed, prorate between the above 15% and
25% losses in
accordance with the fraction of expected or actual condensate loss.
The above guidance assumes that DES-generated heat is used for heat
in the connected building, and DES-generated cooling is used for cooling in
the connected building. If the DES produces heating that is then converted
to cooling for the connected building using absorption chillers or other
similar technology, this guidance must be modified (see CHP Modeling
Guidance).Path 3. Streamlined DES modelingPath 3 is applicable for
simple district energy systems. The energy model scope accounts for both
downstream equipment and upstream equipment and also requires calculation
of the district energy average efficiencies using either the modeling or
monitoring methods. *Energy rates* Use Streamlined DES Modeling in the
calculator provided by USGBC to allocate the energy costs to the results of
the model for each district energy source, in lieu of the purchased energy
rates, to determine the baseline energy cost. *Baseline plant* Calculate
the average annual efficiency values for each district or central plant
fuel source used to generate and distribute the thermal energy, based on
ASHRAE 90.1–2010, Appendix G, baseline case requirements. These values
depend on the ASHRAE 90.1–2010 system type that would be selected for the
building if the baseline case were modeled with on-site equipment. The
calculations for baseline cost per district energy source are the same as
those for the proposed case model, except that the average efficiency is
constant. *Proposed plant* Determine a single value for average annual
efficiency, including thermal losses and distribution energy, for each
district or central plant fuel source used to generate and distribute the
thermal energy. For example, for chilled water:
Best regards.
*Victor Moreno*
*Consultor energético y sostenibilidad en edificaciónLEED AP, BREEAM
Asesor, CEM, CMVP, CxA+34 699 135 788*
El vie, 30 ago 2024 a las 13:29, Chris Yates via Bldg-sim (<
bldg-sim at lists.onebuilding.org>) escribió:
> Hello,
>
>
>
> I’m modelling a Commercial Interior to LEED v4 ID+C. It’s roughly a single
> floor with purchased heating and cooling piped in to fan coil terminals and
> a DOAS.
>
>
>
> I’m a unclear regarding the baseline, especially the envelope.
> Furthermore, the guidance that is given seems to go against my expectation.
>
>
>
> BASELINE
>
> My expectation
>
> What LEED seems to say
>
> Envelope
>
> As existing shell
>
> Same as section 5. Explicitly ignore item (f), existing envelope
>
> Chiller/ boiler
>
> Not in tenants scope so as existing
>
> Not clear but seems to be regular App G/ System 7, etc.
>
> DOAS
>
> Not in tenants scope so as existing
>
>
>
> I have a the 2011 version of “Advanced Energy Modelling for LEED” and
> can’t seem to find any more detail in there.
>
>
>
> Are there any good, current, prescriptive sources for how to model this?
> Or any simple answers?!
>
>
>
> Kind regards
>
>
>
> Chris Yates C Eng MCIBSE LCEA
>
>
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