Calculation Of The Proposed Design And Baseline Building Performance
Releasing January 2026
Building Performance Calculations
Develop the simulation model for calculating the proposed and baseline building performance in accordance with the requirements in Table G3.1.
Baseline HVAC System Type and Description
Determine HVAC systems in the baseline building design using the following order of priority: the building type with the largest conditioned floor area, number of floors (including floors above and below grade but excluding floors solely devoted to parking), gross conditioned floor area, and climate zone as specified in Table G3.1.1-3, which must conform with the system descriptions in Table G3.1.1-4. For Systems 1, 2, 3, 4, 9, 10, 11, 12, and 13, model each thermal block with its own HVAC system. For Systems 5, 6, 7, and 8, model each floor with a separate HVAC system. Floors with identical thermal blocks can be grouped for modeling purposes.
Use additional system types for non predominant conditions (i.e., residential/nonresidential) if those conditions apply to more than 1900 m² of conditioned floor area. If the baseline HVAC system type is 5, 6, 7, 8, 9, 10, 11, 12, or 13, use separate single-zone systems conforming with the requirements of system 3 or 4 for any HVAC zones that have occupancy, internal gains, or schedules that differ significantly from the rest of the zones served by the system. Zones with total peak internal gains that differ by 31.2 W/m² or more from the average of other zones served by the system, or schedules that differ by more than 40 equivalent full-load hours per week, are considered to differ significantly. Examples include natatoriums and continually occupied security areas, but this exception does not apply to computer rooms.
For laboratory spaces in a building with total laboratory exhaust rate greater than 7100 L/s, use a single system of type 5 or 7 serving only those spaces. Model the lab exhaust fan as constant kilowatts reflecting constant-volume stack discharge with outdoor air bypass. For thermal zones designed with heating-only systems in the proposed design serving storage rooms, stairwells, vestibules, electrical/mechanical rooms, and restrooms not exhausting or transferring air from mechanically cooled thermal zones, use system type 9 or 10 in the baseline building design. If the baseline HVAC system type is 9 or 10, use additional system types for all HVAC zones that are mechanically cooled in the proposed design.
Computer rooms in buildings with total computer room peak cooling load exceeding 880 kW, or exceeding 175 kW where the baseline HVAC system type is 7 or 8, must use System 11. All other computer rooms must use System 3 or 4. For hospitals, use System 5 or 7 in all climate zones depending on building type.
Design Model
The simulation model of the proposed design must be consistent with the design documents, including proper accounting of fenestration and opaque building envelope types and areas, interior lighting power and controls, HVAC system types, sizes, and controls, and service water-heating systems and controls. Model all end-use load components within and associated with the building, including but not limited to exhaust fans, parking garage ventilation fans, snow-melt and freeze-protection equipment, facade lighting, swimming pool heaters and pumps, elevators and escalators, refrigeration, and cooking. Where the simulation program does not specifically model the functionality of the installed system, use spreadsheets or other documentation of the assumptions to generate the power demand and operating schedule of the systems.
Model the baseline building design with the same number of floors and identical conditioned floor area as the proposed design.
Simulate all conditioned spaces in the proposed design as being both heated and cooled even if no heating or cooling system is to be installed.
Exception: Spaces designed with heating-only systems serving storage rooms, stairwells, vestibules, electrical/mechanical rooms, and restrooms not exhausting or transferring air from mechanically cooled thermal zones shall not be modeled with mechanical cooling.
Develop the baseline building design by modifying the proposed design as described in Section G3. Except as specifically instructed, model all building systems and equipment identically in the proposed design and baseline building design.
When the Performance Rating Method is applied to buildings in which energy-related features have not yet been designed (e.g., a lighting system), model those yet-to-be-designed features in the proposed design to comply with but not exceed the requirements of this standard as described in Table G3.1, Nos. 6, 10, 11, and 12. Where the space classification for a space is not known, categorize the space as an office space.
Where the baseline building systems and equipment are permitted to be different from the proposed design but are not prescribed in this appendix, determine the baseline based on the following, in order of priority: (a) requirements in Sections 5 through 10, or (b) requirements of other efficiency or equipment codes or standards applicable to the design of the building systems and equipment.
Additions and Alterations
Building models may exclude parts of the existing building, provided all of the following conditions are met:
(a) Work performed in excluded parts of the building must meet the requirements of Sections 5 through 10.
(b) Excluded parts of the building are served by HVAC systems that are entirely separate from those serving parts of the building included in the model.
(c) Design space temperature and HVAC system operating set points and schedules on either side of the boundary between included and excluded parts are essentially the same.
(d) If a declining block or similar utility rate is being used in the analysis, and the excluded and included parts are on the same utility meter, the rate must reflect the utility block or rate for the building plus the addition.
If the proposed design excludes parts of the existing building, the baseline building design must exclude them as well.
When modeled, unmodified existing building components must follow the same rules as new and modified building components.
When modeled, unmodified existing building components must follow the same rules as new and modified building components.
Space Use Classification
Determine the space use classification within each thermal block using the space type lighting classifications in accordance with Section 9.6.1.
Exception: Where space types neither exist nor are designated in design documents, specify use type in accordance with Section 9.5.1.
The user may simplify the placement of the various space types within the building model, provided that building total areas and orientation of glazed exterior walls for each space type are accurate.
Same as proposed design.
Schedule
Use schedules capable of modeling hourly variations in occupancy, lighting power, miscellaneous equipment power, thermostat set points, and HVAC system operation. The schedules must be typical of the proposed building type as determined by the designer and approved by the rating authority.
Temperature and Humidity Schedules: Temperature and humidity control set points and schedules as well as temperature control throttling range must be the same for proposed design and baseline building design.
Same as proposed design.
Exceptions:
1. Set points and schedules for HVAC systems that automatically provide occupant thermal comfort via means other than directly controlling the air dry-bulb and wet-bulb temperature may be allowed to differ, provided that equivalent levels of occupant thermal comfort are demonstrated via the methodology in ASHRAE Standard 55, Section 5.3.3, "Elevated Air Speed," or Standard 55, Appendix B, "Computer Program for Calculation of PMV-PPD."
2. Schedules may be allowed to differ between proposed design and baseline building design when necessary to model nonstandard efficiency measures, provided that the revised schedules have been approved by the rating authority. Measures that may warrant use of different schedules include but are not limited to automatic lighting controls, automatic natural ventilation controls, automatic demand control ventilation controls, and automatic controls that reduce service water-heating loads. In no case shall schedules differ where the controls are manual (e.g., manual operation of light switches or manual operation of windows).
HVAC Fan Schedules: Schedules for HVAC fans that provide outdoor air for ventilation must run continuously whenever spaces are occupied and must be cycled ON and OFF to meet heating and cooling loads during unoccupied hours.
Exceptions:
1. Where no heating and/or cooling system is to be installed, and a heating or cooling system is being simulated only to meet the requirements described in this table, heating and/or cooling system fans shall not be simulated as running continuously during occupied hours but shall be cycled ON and OFF to meet heating and cooling loads during all hours.
2. HVAC fans must remain on during occupied and unoccupied hours in spaces that have health- and safety-mandated minimum ventilation requirements during unoccupied hours.
3. HVAC fans must remain on during occupied and unoccupied hours in systems primarily serving computer rooms.
Fan schedules may be allowed to differ when Section G3.1.1 (c) applies.
Building Envelope
Model all components of the building envelope as shown on architectural drawings or as built for existing building envelopes.
Exceptions: The following building elements are permitted to differ from architectural drawings:
1. All uninsulated assemblies (e.g., projecting balconies, perimeter edges of intermediate floor slabs, concrete floor beams over parking garages, roof parapets) must be separately modeled using either: (a) separate model of each assembly within the energy simulation model, or (b) separate calculation of the U-factor for each assembly, then averaging these U-factors with larger adjacent surfaces using an area-weighted average method. Any other building envelope assembly that covers less than 5% of the total area of that assembly type (e.g., exterior walls) need not be separately described, provided that it is similar to an assembly being modeled. If not separately described, the area of a building envelope assembly must be added to the area of an assembly of that same type with the same orientation and thermal properties.
2. Exterior surfaces whose azimuth orientation and tilt differ by less than 45 degrees and are otherwise the same may be described as either a single surface or by using multipliers.
3. Model the exterior roof surface using the aged solar reflectance and thermal emittance determined in accordance with Section 5.5.3.1.1(a). Where aged test data are unavailable, the roof surface may be modeled with a reflectance of 0.30 and a thermal emittance of 0.90. <br><br>4. Manual fenestration shading devices, such as blinds or shades, must be modeled or not modeled the same as in the baseline building design. Automatically controlled fenestration shades or blinds must be modeled. Permanent shading devices, such as fins, overhangs, and light shelves must be modeled. <br><br>5. Automatically controlled dynamic glazing may be modeled. Manually controlled dynamic glazing must use the average of the minimum and maximum SHGC and VT.
Model infiltration using the same methodology and adjustments for weather and building operation in both the proposed design and the baseline building design. These adjustments must be made for each simulation time step and must account for but not be limited to weather conditions and HVAC system operation, including strategies that are intended to positively pressurize the building. The air leakage rate of the building envelope (I₇₅Pa) at a fixed building pressure differential of 75 Pa must be 3.0 L/s·m² for buildings providing verification in accordance with Section 5.9.1.2. The air leakage rate of the building envelope must be converted to appropriate units for the simulation program using one of the methods in Section G3.1.1.4.
Exception: When whole-building air leakage testing, in accordance with Section 5.4.3.1.1, is specified during design and completed after construction, the proposed design air leakage rate of the building envelope must be as measured.
Assume equivalent dimensions for each building envelope component type as in the proposed design; i.e., the total gross area of walls must be the same in the proposed design and baseline building design. The same must be true for the areas of roofs, floors, and doors, and the exposed perimeters of concrete slabs on grade must also be the same in the proposed design and baseline building design. The following additional requirements apply to the modeling of the baseline building design:
a. Orientation: Generate the baseline building performance by simulating the building with its actual orientation and again after rotating the entire building 90, 180, and 270 degrees, then averaging the results. The building must be modeled so that it does not shade itself.
Exceptions:
1. If it can be demonstrated to the satisfaction of the rating authority that the building orientation is dictated by site considerations.
2. Buildings where the vertical fenestration area on each orientation varies by less than 5%.
b. Opaque Assemblies: Opaque assemblies used for new buildings, existing buildings, or additions must conform with assemblies detailed in Normative Appendix A and must match the appropriate assembly maximum U-factors in Tables G3.4-1 through G3.4-8:
• Roofs—Insulation entirely above deck (A2.2)
• Above-grade walls—Steel-framed (A3.3)
• Below-grade walls—Concrete block (A4)
• Floors—Steel-joist (A5.3)
• Slab-on-grade floors must match the F-factor for unheated slabs from the same tables (A6)
• Opaque door types must be of the same type of construction as the proposed design and conform to the U-factor requirements from the same tables (A7)
c. Vertical Fenestration Areas: For building area types included in Table G3.1.1-1, vertical fenestration areas for new buildings and additions must equal that in Table G3.1.1-1 based on the area of gross above-grade walls that separate conditioned spaces and semi-heated spaces from the exterior. Where a building has multiple building area types, each type must use the values in the table. The vertical fenestration must be distributed on each face of the building in the same proportion as in the proposed design. For building areas not shown in Table G3.1.1-1, vertical fenestration areas for new buildings and additions must equal that in the proposed design or 40% of gross above-grade wall area, whichever is smaller, and must be distributed on each face of the building in the same proportions in the proposed design. The fenestration area for an existing building must equal the existing fenestration area prior to the proposed work and must be distributed on each face of the building in the same proportions as the existing building.
d. Vertical Fenestration Assemblies: Fenestration for new buildings, existing buildings, and additions must comply with the following:
• Fenestration U-factors must match the appropriate requirements in Tables G3.4-1 through G3.4-8 for the applicable glazing percentage for Uₐₗₗ
• Fenestration SHGCs must match the appropriate requirements in Tables G3.4-1 through G3.4-8 using the value for SHGCₐₗₗ for the applicable vertical glazing percentage
• All vertical fenestration must be assumed to be flush with the exterior wall, and no shading projections shall be modeled
• Manual window shading devices such as blinds or shades are not required to be modeled
e. Skylights and Glazed Smoke Vents: Skylight area must be equal to that in the proposed design or 3%, whichever is smaller. If the skylight area of the proposed design is greater than 3%, baseline skylight area must be decreased by an identical percentage in all roof components in which skylights are located to reach 3%. Skylight orientation and tilt must be the same as in the proposed design. Skylight U-factor and SHGC properties must match the appropriate requirements in Tables G3.4-1 through G3.4-8 using the value and the applicable skylight percentage.
f. Roof Solar Reflectance and Thermal Emittance: Model the exterior roof surfaces using a solar reflectance of 0.30 and a thermal emittance of 0.90.
g. Roof Albedo: Model all roof surfaces with a reflectivity of 0.30.
h. Air Leakage: The air leakage rate of the building envelope (I₇₅Pa) at a fixed building pressure differential of 75 Pa of water must be 5.1 L/s·m².
Lighting
Determine lighting power in the proposed design as follows:
a. Where a complete lighting system exists, use the actual lighting power for each thermal block in the model.
b. Where a complete lighting system has been designed and submitted with design documents, determine lighting power in accordance with Sections 9.1.3 and 9.1.4.
c. Where lighting neither exists nor is submitted with design documents, lighting must comply with but not exceed the requirements of Section 9. Determine lighting power in accordance with the Building Area Method.
d. Lighting system power must include all lighting system components shown or provided for on the plans (including lamps and ballasts and task and furniture-mounted fixtures).
e. For dwelling units, hotel/motel guest rooms, and other spaces in which lighting systems are connected via receptacles and are not shown on design documents, lighting power used in the simulation must equal the lighting power allowance in Table 9.6.1 for the appropriate space type or as designed, whichever is greater. For dwelling units, lighting power used in the simulation must equal 6.5 W/m² or as designed, whichever is greater.
Exception: Lighting use can be reduced for the portion of the space illuminated by the specified fixtures provided that they maintain the same illuminance level as in the baseline. Such reduction must be demonstrated by calculations.
f. Model lighting power for parking garages and building façades.
g. At a minimum, the proposed design must contain the mandatory automatic lighting controls specified in Section 9.4.1 (e.g., automatic daylight responsive controls, occupancy sensors, programmable controls, etc.). Model these controls in accordance with (h) and (i).
h. Model automatic daylighting responsive controls directly in the proposed design or through schedule adjustments determined by a separate daylighting analysis approved by the rating authority. Modeling and schedule adjustments must separately account for primary sidelighted areas, secondary sidelighted areas, and top lighted areas.
i. Model other automatic lighting controls included in the proposed design directly in the building simulation by reducing the lighting schedule each hour by the occupancy sensor reduction factors in Table G3.7 for the applicable space type. Take this reduction only for lighting controlled by the occupancy sensors. Credit for other programmable lighting control in buildings less than 500 m² can be taken by reducing the lighting schedule each hour by 10%.
Determine interior lighting power in the baseline building design using the values in Table G3.7.
Model lighting with the automatic shutoff controls in buildings >500 m² and occupancy sensors in employee lunch and break rooms, conference/meeting rooms, and classrooms (not including shop classrooms, laboratory classrooms, and preschool through 12th-grade classrooms).
Reflect these controls in the baseline building design lighting schedules. Do not model additional automatic lighting controls, e.g., automatic controls for daylight utilization and occupancy sensors in space types not listed above, in the baseline building design.
Model exterior lighting in areas identified as "Tradable Surfaces" in Table G3.6 with the baseline lighting power shown in Table G3.6. Model other exterior lighting the same in the baseline building design as in the proposed design.
Thermal Blocks
HVAC Zones Designed
Where HVAC zones are defined on HVAC design drawings, model each HVAC zone as a separate thermal block.
Exceptions: Different HVAC zones may be combined to create a single thermal block or identical thermal blocks to which multipliers are applied, provided that all of the following conditions are met:
1. The space use classification is the same throughout the thermal block, or all of the zones have peak internal loads that differ by less than 31.2 W/m² from the average.
2. All HVAC zones in the thermal block that are adjacent to glazed exterior walls and glazed semi exterior walls face the same orientation or their orientations vary by less than 45 degrees.
3. All of the zones are served by the same HVAC system or by the same kind of HVAC system.
4. All of the zones have schedules that differ by 40 or less equivalent full-load hours per week.
Same as proposed design.
HVAC Zones Not Designed
Where the HVAC zones and systems have not yet been designed, define thermal blocks based on similar internal load densities, occupancy, lighting, thermal and space temperature schedules, and in combination with the following guidelines:
a. Assume separate thermal blocks for interior and perimeter spaces. Interior spaces are those located greater than 4.6 m from an exterior wall or semi exterior wall. Perimeter spaces are those located within 4.6 m of an exterior wall or semi-exterior wall. A separate thermal zone does not need to be modeled for areas adjacent to semi-exterior walls that separate semi-heated space from conditioned space.
b. Assume separate thermal blocks for spaces adjacent to glazed exterior walls or glazed semi exterior walls; provide a separate zone for each orientation, except that orientations that differ by less than 45 degrees may be considered to be the same orientation. Each zone must include all floor area that is 4.6 m or less from a glazed perimeter wall, except that floor area within 4.6 m of glazed perimeter walls having more than one orientation shall be divided proportionately between zones.
c. Assume separate thermal blocks for spaces having floors that are in contact with the ground or exposed to ambient conditions from zones that do not share these features.
d. Assume separate thermal blocks for spaces having exterior ceiling or roof assemblies from zones that do not share these features.
Same as proposed design.
Multifamily Residential Buildings
Model residential spaces using at least one thermal block per dwelling unit, except that those units facing the same orientations may be combined into one thermal block. Combine corner units and units with roof or floor loads only with units sharing these features.
Same as proposed design.
HVAC Systems
Determine the HVAC system type and all related performance parameters in the proposed design, such as equipment capacities and efficiencies, as follows:
a. Where a complete HVAC system exists, the model must reflect the actual system type using actual component capacities and efficiencies.
b. Where an HVAC system has been designed and submitted with design documents, the HVAC model must be consistent with design documents. Adjust mechanical equipment efficiencies from actual design conditions to the standard rating conditions specified in Section 6.4.1 if required by the simulation model. Where efficiency ratings include supply fan energy, adjust the efficiency rating to remove the supply fan energy from the efficiency rating in the baseline building design. Do not use the equations in Section G3.1.2.1 in the proposed design. Model the proposed design HVAC system using manufacturers' full- and part-load data for the HVAC system without fan power.
c. Where no heating system exists or no heating system has been submitted with design documents, the system type must be the same system as modeled in the baseline building design and must comply with but not exceed the requirements of Section 6.
d. Where no cooling system exists or no cooling system has been submitted with design documents, the cooling system type must be the same as modeled in the baseline building design and must comply with the requirements of Section 6.
Exception: Spaces using baseline HVAC system types 9 and 10.
The HVAC systems in the baseline building design must be of the type and description specified in Section G3.1.1, must meet the general HVAC system requirements specified in Section G3.1.2, and must meet any system-specific requirements in Section G3.1.3 that are applicable to the baseline HVAC system types.
If the proposed design includes humidification, then the baseline building design must use adiabatic humidification.
Exception: If the proposed building humidification system complies with Section 6.5.2.4, then the baseline building design must use nonadiabatic humidification.
For systems serving computer rooms, the baseline building design must not have reheat for the purpose of dehumidification. Model fossil fuel systems using natural gas as their fuel source.
Exception: For fossil fuel systems where natural gas is not available for the proposed building site as determined by the rating authority, model the baseline HVAC systems using propane as their fuel.
Service Water-Heating Systems
Determine the service water-heating system type and all related performance parameters, such as equipment capacities and efficiencies, in the proposed design as follows:
a. Where a complete service water-heating system exists, the proposed design must reflect the actual system type using actual component capacities and efficiencies.
b. Where a service water-heating system has been designed and submitted with design documents, the service water-heating model must be consistent with design documents.
c. Where no service water-heating system exists or has been designed and submitted with design documents but the building will have service water-heating loads, model a service water-heating system that matches the system type in the baseline building design, serves the same water-heating loads, and complies with but does not exceed the requirements of Section 7.
d. For buildings that will have no service water-heating loads, do not model a service water-heating system.
e. Where a combined system has been specified to meet both space heating and service water-heating loads, the proposed design must reflect the actual system type using actual component capacities and efficiencies.
f. Do not model piping losses.
The service water-heating system in the baseline building design must be as specified in Table G3.1.1-2 and conform with the following conditions:
a. Where a complete service water-heating system exists or a new service water-heating system has been specified, model one service water-heating system for each building area type in the proposed building. Size each system according to the provisions of Section 7.4.1, and the equipment must match the minimum efficiency requirements in Section 7.4.2.
b. Where no service water-heating system exists or has been specified but the building will have service water-heating loads, model one service water-heating system for each anticipated building area type in the proposed design. Each system must meet the minimum efficiency requirements of Section 7.4.2 and be modeled identically to the proposed design.
c. For buildings that will have no service water-heating loads, do not model service water-heating.
d. For large, 24-hour-per-day facilities that meet the prescriptive criteria for use of condenser heat recovery systems described in Section 6.5.6.2, include a system meeting the requirements of that section in the baseline building design regardless of the exceptions to Section 6.5.6.2.
Exception: If a condenser heat recovery system meeting the requirements described in Section 6.5.6.2 cannot be modeled, the requirement for including such a system in the actual building must be met as a prescriptive requirement in accordance with Section 6.5.6.2, and no heat recovery system shall be included in the proposed design or baseline building design.
e. Calculate service water-heating energy consumption explicitly based upon the volume of service water heating required and the entering makeup water and the leaving service water-heating temperatures. Estimate entering water temperatures based upon the location. Base leaving temperatures upon the end-use requirements.
f. Where recirculation pumps are used to ensure prompt availability of service water-heating at the end use, calculate the energy consumption of such pumps explicitly.
g. Service water loads and use must be the same for both the proposed design and baseline building design and must be documented by the calculation procedures described in Section 7.4.1.
Exceptions:
1. Service water-heating use can be demonstrated to be reduced by documented water conservation measures that reduce the physical volume of service water required. Examples include, but are not limited to, low-flow shower heads and dishwashers. Such reduction must be demonstrated by calculations. The baseline flow rates shall be determined as described in Table G3.1, No. 1, and the calculation methodology must be approved by the authority having jurisdiction.
2. Service water-heating energy consumption can be demonstrated to be reduced by reducing the required temperature of service mixed water, by increasing the temperature, or by increasing the temperature of the entering makeup water. Examples include alternative sanitizing technologies for dishwashing and heat recovery to entering makeup water. Such reduction must be demonstrated by calculations.
3. Service water heating use can be demonstrated to be reduced by reducing the hot fraction of mixed water to achieve required operational temperature. Examples include shower or laundry heat recovery to incoming cold-water supply, reducing the hot-water fraction required to meet required mixed-water temperature. Such reduction must be demonstrated by calculations.
h. Model gas storage water heaters using natural gas as their fuel.
Exception: Where natural gas is not available for the proposed building site, as determined by the rating authority, model gas storage water heaters using propane as their fuel.
i. Do not model piping losses.
Receptacle and Other Loads
Estimate receptacle and process loads, such as those for office and other equipment, based on the building area type or space type category and assume them to be identical in the proposed design and baseline building design, except as specifically approved by the rating authority only when quantifying performance that exceeds the requirements of Standard 90.1 but not when the Performance Rating Method is used as an alternative path for minimum standard compliance in accordance with Section 4.2.1.1. Always include these loads in simulations of the building and when calculating the proposed building performance and the baseline building performance as required by Section G1.2.1.
Exception: When receptacle controls installed in spaces where not required by Section 8.4.2 are included in the proposed building design, reduce the hourly receptacle as follows:
RPC = RC × 10%
where
RPC = receptacle power credit
RC = percentage of all controlled receptacles EPSpro = EPSbas × (1 – RPC)
EPSbas = baseline equipment power hourly schedule (fraction)
EPSpro = proposed equipment power hourly schedule (fraction)
a. Where power and other systems covered by Sections 8 and 10 have been designed and submitted with design documents, determine those systems in accordance with Sections 8 and 10.
b. Where power and other systems covered by Sections 8 and 10 have not been submitted with design documents, those systems must comply with but not exceed the requirements of those sections.
Model motors as having the efficiency ratings found in Table G3.9.1. Model other systems covered by Section 10 and miscellaneous loads as identical to those in the proposed design, including schedules of operation and control of the equipment. Energy used for cooking equipment, receptacle loads, computers, medical or laboratory equipment, and manufacturing and industrial process equipment not specifically identified in the standard power and energy rating or capacity of the equipment must be identical between the proposed building performance and the baseline building performance. Receptacle schedules must be the same as the proposed design before the receptacle power credit is applied.
Exceptions: When quantifying performance that exceeds the requirements of Standard 90.1 (but not when using the Performance Rating Method as an alternative path for minimum standard compliance per Section 4.2.1.1), variations of the power requirements, schedules, or control sequences of the equipment modeled in the baseline building design from those in the proposed design must be approved by the rating authority based on documentation described in Table G3.1, No. 1, or that the equipment installed in the proposed design represents a significant verifiable departure from documented current conventional practice. The burden of this documentation is to demonstrate that accepted conventional practice would result in baseline building equipment different from that installed in the proposed design. Do not change occupancy and occupancy schedules.
Modeling Limitations to the Simulation Program
If the simulation program cannot model a component or system included in the proposed design explicitly, substitute a thermodynamically similar component model that can approximate the expected performance of the component that cannot be modeled explicitly.
Same as proposed design.
Exterior Conditions
a. Shading by Adjacent Structures and Terrain: The effect that structures and significant vegetation or topographical features have on the amount of solar radiation being received by a structure must be adequately reflected in the computer analysis. All elements whose effective height is greater than their distance from a proposed building and whose width facing the proposed building is greater than one-third that of the proposed building must be accounted for in the analysis.
Same as proposed design.
b. Ground Temperatures for Below-Grade Wall and Basement Floor Heat-Loss Calculations: It is acceptable to use either an annual average ground temperature or monthly average ground temperatures for calculation of heat loss through below-grade walls and basement floors.
Same as proposed design.
c. Water Main Temperatures for Service Water-Heating Calculations: It is acceptable to use either an annual water main supply temperature or monthly average water main supply temperatures for calculating service water heating. If annual or monthly water main supply temperatures are not available from the local water utility, annual average ground temperatures may be used.
Same as proposed design.
Distribution Transformers
Model low-voltage dry-type distribution transformers if the transformers in the proposed design exceed the efficiency required in Table 8.4.4.
Model low-voltage dry-type distribution transformers only if the proposed design transformers exceed the efficiency requirements of Table 8.4.4. If modeled, use the efficiency requirements from Table 8.4.4. The ratio of the capacity to peak electrical load of the transformer must be the same as the ratio in the proposed design.
Elevators
Where the proposed design includes elevators, include the elevator motor, ventilation fan, and light load in the model. Model the cab ventilation fan and lights with the same schedule as the elevator motor.
Where the proposed design includes elevators, model the baseline building design to include the elevator cab motor, ventilation fans, and lighting power.
Calculate the elevator peak motor power as follows:
kW = (weight of car + rated load – counterweight) × speed of car × 0.00981/h<sub>mechanical</sub> <br><br>P<sub>m</sub> = kW/h<sub>motor</sub> <br><br>where <br>
Weight of Car = the proposed design elevator car weight, kg
Rated Load = the proposed design elevator load at which to operate, kg
Counterweight of Car = the elevator car counterweight, from Table G3.9.2, kg
Speed of Car = the speed of the proposed elevator, m/s
hmechanical = the mechanical efficiency of the elevator from Table G3.9.2
hmotor = the motor efficiency from Table G3.9.2
Pm = peak elevator motor power, kW
Model the elevator motor use with the same schedule as the proposed design.
When included in the proposed design, the baseline elevator cab ventilation fan must be 0.69 W/L·s and the lighting power density must be 33.79 W/m²; both operate continuously.
Refrigeration
Where refrigeration equipment in the proposed design is rated in accordance with AHRI 1200, model the rated energy use. Otherwise, model the proposed design using the actual equipment capacities and efficiencies.
Where refrigeration equipment is specified in the proposed design and listed in Tables G3.10.1 and G3.10.2, model the baseline building design as specified in Tables G3.10.1 and G3.10.2 using the actual equipment capacities. <br><br>If the refrigeration equipment is not listed in Tables G3.10.1 and G3.10.2, model the baseline building design the same as the proposed design.
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