Energy Cost Budget Method
The Energy Cost Budget (ECB) Method is an alternative compliance path to the prescriptive provisions of ASHRAE 90.1. It may be employed for evaluating the compliance of all proposed designs except those with no mechanical system.
The ECB Method provides design flexibility by allowing trade-offs between different building systems and components, provided the overall energy cost of the proposed design does not exceed the energy cost budget established by the baseline design.
Trade-Offs
When the building permit applies to less than the whole building, only calculation parameters related to the systems covered by the permit may vary between the proposed design and the energy cost budget. Parameters relating to unmodified existing conditions or future building components must remain identical in both the energy cost budget and design energy cost calculations.
This requirement ensures that partial building renovations or phased construction projects are evaluated fairly by limiting the scope of trade-offs to only the systems being modified under the current permit, preventing manipulation of baseline assumptions for existing or future conditions that are outside the scope of the current work.
Building Envelope Approval
For new buildings or additions, the Energy Cost Budget Method results cannot be submitted for building permit approval to the authority having jurisdiction until the building envelope design has been submitted for approval.
The following steps illustrate the process undertaken on the Better Buildings project to meet the requirements of the Energy Cost Budget Method.
This requirement ensures that the building envelope, which forms the foundation of energy performance, is designed and approved first before allowing trade-offs with other building systems, preventing scenarios where an inefficient envelope is compensated solely through mechanical system upgrades and ensuring a balanced approach to energy efficiency.
Compliance
To demonstrate compliance using the Energy Cost Budget Method, the proposed building design must satisfy all of the following requirements:
Mandatory Provisions
The design must comply with the mandatory provisions specified for building envelope, HVAC, service hot water, power, lighting and other equipment.
This requirement establishes a performance floor by ensuring that certain critical efficiency measures are implemented regardless of trade-offs, preventing the use of excessively inefficient components or systems even if the overall energy cost target is met.
Energy Cost Performance
The design energy cost, as calculated in Calculation of Design Energy Cost and Energy Cost Budget, must not exceed the energy cost budget as calculated by the simulation program described in Simulation Program - General Requirements.
The energy cost budget and design energy cost calculations are used solely for determining compliance with this standard. They are not predictions of actual energy consumption or costs of the proposed design after construction. Actual performance will differ from these calculations due to variations in weather, occupancy patterns, operational practices, and other real-world factors.
This requirement establishes the fundamental comparison metric for the Energy Cost Budget Method while clearly communicating that compliance calculations are standardized modeling exercises for code purposes, not guarantees of actual building performance, managing expectations and preventing misinterpretation of the analysis results.
Installed Equipment Efficiency
The energy efficiency level of all installed components and systems must meet or exceed the efficiency levels used to calculate the design energy cost.
This requirement prevents value engineering or substitution of lower-efficiency equipment after approval is granted, ensuring that the building as constructed will perform at least as well as the approved design model predicted.
Verification and Commissioning
All verification, testing, and commissioning requirements must be met.
This requirement ensures that building systems are properly installed, calibrated, and functioning as designed, bridging the gap between design intent and actual performance to maximize the likelihood that the building will achieve its modeled energy efficiency in operation.
Simulation Program
Better Building is a computer-based program for analyzing energy consumption in buildings. Better Building must be approved by the adopting authority and demonstrate the capability to explicitly model all of the following:
Annual Hourly Analysis: 8760 hours per year
Schedule Variations: Hourly variations in occupancy, lighting power, miscellaneous equipment power, thermostat set points, and HVAC system operation, defined separately for each day of the week and holidays
Thermal Mass Effects: Dynamic heat storage and release characteristics
Multiple Zones: Ten or more thermal zones
Equipment Performance: Part-load performance curves for mechanical equipment
Correction Factors: Capacity and efficiency correction curves for mechanical heating and cooling equipment
Economizer Controls: Air-side and fluid economizers with integrated control
Baseline Characteristics: Budget building design characteristics unless otherwise specified in the Calculation of Design Energy Cost and Energy Cost Budget
These minimum capabilities ensure the simulation program can accurately capture the dynamic, time-varying nature of building energy use, including real-world operating conditions such as part-load performance, diverse occupancy patterns, thermal storage effects, and sophisticated HVAC control strategies that significantly impact actual building energy consumption.
Output Requirements
Better Building has the ability to directly determine the design energy cost and energy cost budget, and produce hourly reports of energy use by energy source suitable for calculating the design energy cost and energy cost budget through separate calculations.
This requirement ensures the simulation outputs provide the necessary data in a format that can be directly used for compliance determination and cost comparison between the proposed design and baseline building.
Design Load Calculations
Better Building is capable of performing design load calculations to determine required HVAC equipment capacities and air and water flow rates for both the proposed design and the budget building design.
This requirement ensures consistency between equipment sizing methodology and energy simulation inputs, preventing discrepancies where inappropriately sized equipment would produce unrealistic energy consumption predictions and compromise the validity of the compliance analysis.
Software Verification
Better Building has been tested according to ASHRAE Standard 140, except for Sections 7 and 8. The test results and modeler reports are publicly available website and include the test results of the simulation program along with the results of the other simulation programs included in ASHRAE Standard 140, Annexes B8 and B16. The modeler report in Standard 140, Annex A2, Attachment A2.7 has been completed for results exceeding the maximum or falling below the minimum of the reference values or for missing results.
These requirements ensure that simulation programs used for envelope trade-off compliance have verified calculation capabilities, can accurately model all relevant building systems and control strategies, and have been validated against industry-standard test suites to demonstrate reliability and accuracy in predicting building energy performance.
Climatic Data
Better Building performs simulations using hourly values of climatic data, including temperature, humidity, solar radiation, and wind speed and direction from representative climatic data for the proposed design building envelope location.
For cities or urban regions for which several climatic data sources are available and for locations for which weather data are not available, the designer shall select available weather data that represent the climate at the construction site. Selected weather data shall be approved by the authority having jurisdiction.
This requirement ensures that both the proposed design and baseline building are evaluated under identical, representative climate conditions, providing an equitable comparison while preventing manipulation of compliance results through inappropriate weather data selection.
Renewable, Recovered, and Purchased Energy
On-Site Renewable Energy and Site-Recovered Energy
Site-recovered energy is not considered purchased energy and must be subtracted from the proposed design energy consumption prior to calculating the design energy cost.
On-site renewable energy must also be subtracted from the proposed design energy consumption prior to calculating the design energy cost, provided that the building owner meets one of the following conditions: owns the on-site renewable energy system, has signed a lease agreement for the system for at least 15 years, or has signed a contractual agreement to purchase energy generated by the system for at least 15 years.
The reduction in design energy cost associated with on-site renewable energy cannot exceed 5% of the calculated energy cost budget. This requirement allows credit for on-site renewable and recovered energy systems while ensuring long-term commitment to these systems through ownership or contractual agreements, and prevents over-reliance on renewable energy credits by capping the allowable cost reduction to maintain baseline building efficiency standards.
Annual Energy Costs
The design energy cost and energy cost budget must be determined using rates for purchased energy (such as electricity, gas, oil, propane, steam, and chilled water) that are approved by the adopting authority.
Where on-site renewable energy or site-recovered energy is used, the budget building design must be based on the energy source used as the backup energy source, or electricity if no backup energy source has been specified.
Where the proposed design includes on-site electricity generation systems other than on-site renewable energy systems, the baseline design must include the same generation systems excluding its site-recovered energy.
This requirement ensures consistent economic comparison between proposed and baseline designs by establishing standardized energy cost assumptions and appropriate baseline modeling rules for buildings with on-site generation, preventing unfair advantages while recognizing legitimate energy production capabilities.
Compliance Calculations
The design energy cost and energy cost budget must be calculated using the same simulation program, the same weather data, and the same purchased energy rates.
This requirement ensures a fair and accurate comparison between the proposed design and baseline building by eliminating variables related to modeling methodology, climate assumptions, and economic factors, so that only the actual building design differences affect the compliance outcome.
Exceptional Calculation Methods
When the simulation program does not have the capability to model a specific design feature, material, or device, an exceptional calculation method must be used as approved by the authority having jurisdiction to demonstrate compliance with Section 11. Where there are multiple designs, materials, or devices that the simulation program cannot model, each must be calculated separately and exceptional savings determined for each.
All applications for approval of an exceptional calculation method must include the following: theoretical and empirical information verifying the method's accuracy and step-by-step documentation of the exceptional calculation method performed in sufficient detail to reproduce the results; copies of all spreadsheets used to perform the calculations; a sensitivity analysis of energy consumption when each of the input parameters that are estimated is varied from half to double the assumed value; calculations performed on a time-step basis consistent with the simulation program used; and the energy cost budget and design energy cost calculated both with and without the exceptional calculation methods to demonstrate the impact of the exceptional item.
This requirement provides a structured pathway for evaluating innovative or uncommon building components that cannot be modeled by standard simulation programs, while ensuring the alternative calculation methods are technically sound, transparent, reproducible, and thoroughly vetted through sensitivity analysis and authority approval to maintain the integrity of the compliance process.
Calculation of Design Energy Cost and Energy Cost Budget
Simulation Model Development
The simulation model for calculating the design energy cost and the energy cost budget must be developed in accordance with the requirements in the table below.
1. Design Model
The simulation model of the proposed design must be consistent with the design documents, including proper accounting of fenestration and opaque envelope types and area, interior lighting power and controls, HVAC system types, sizes, and controls, and service water-heating systems and controls.
All conditioned spaces in the proposed design must be simulated as being both heated and cooled, even if no cooling or heating system is being installed. 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.
When the Energy Cost Budget Method is applied to buildings in which energy-related features have not yet been designed (e.g., a lighting system), those yet-to-be-designed features must be described in the proposed design so that they minimally comply with applicable mandatory and prescriptive requirements for HVAC, service hot water, power, lighting and other equipment. Where the space classification for a building is not known, the building must be categorized as an office building.
The budget building design must be developed by modifying the proposed design as described in this table. Except as specifically instructed in this table, all building systems and equipment must be modeled identically in the budget building design and proposed design.
2. Additions and Alterations
It is acceptable to demonstrate compliance using building models that exclude parts of the existing building, provided all of the following conditions are met:
• Work to be performed under the current permit application in excluded parts of the building must meet the requirements of Sections 5 through 10
• Excluded parts of the building are served by HVAC systems that are entirely separate from those serving parts of the building that are included in the building model
• Design space temperature and HVAC system operating set points and schedules on either side of the boundary between included and excluded parts of the building are identical
• If a declining block or similar utility rate is being used in the analysis and the excluded and included parts of the building are on the same utility meter, the rate must reflect the utility block or rate for the building plus the addition
Same as proposed design.
3. Space Use Classification
The building area type or space type classifications must be chosen in accordance with the Building Area Method of Calculating Interior Lighting Power Allowance or 9.6.1 Space-by-Space Method of Calculating Interior Lighting Power Allowance. The user or designer must specify the space use classifications using either the building area type or space type categories but must not combine the two types of categories within a single permit application. More than one building area type category may be used for a building if it is a mixed-use facility.
Exception: Where space types neither exist nor are designated in design documents, use type must be specified in accordance with the Building Area Method of Calculating Interior Lighting Power Allowance.
Same as proposed design.
4. Schedules
The schedule types for hourly variations in occupancy, lighting power, miscellaneous equipment power, thermostat set points, and HVAC system operation, defined separately for each day of the week and holidays are required input.
The schedules must be typical of the proposed design as determined by the designer and approved by the authority having jurisdiction. Required schedules must be identical for the proposed design and budget building design.
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.
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 must not be simulated as running continuously during occupied hours but must 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. Dedicated outdoor air supply fans must stay off during unoccupied hours
HVAC fans must remain on during occupied and unoccupied hours in systems primarily serving computer rooms.
Same as proposed design.
5. Building Envelope
All components of the building envelope in the proposed design must be modeled 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. Any 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. If not separately described, the area of a building envelope assembly must be added to the area of the adjacent assembly of that same type
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. The exterior roof surface must be modeled using the aged solar reflectance and thermal emittance determined. Where aged test data are unavailable, the roof surface must be modeled with a solar reflectance of 0.30 and a thermal emittance of 0.90
4. Manually operated fenestration shading devices, such as blinds or shades, must not be modeled. Permanent shading devices, such as fins, overhangs, and light shelves, must be modeled
The budget building design must have identical conditioned floor area and identical exterior dimensions and orientations as the proposed design, except as follows:
• Opaque assemblies, such as roof, floors, doors, and walls, must be modeled as having the same heat capacity as the proposed design but with the minimum U-factor required in Section 5.5 for new buildings or additions and Section 5.1.3 for alterations
• The exterior roof surfaces must be modeled with a solar reflectance and thermal emittance as required. All other roofs must be modeled the same as the proposed design
• No shading projections are to be modeled; fenestration must be assumed to be flush with the wall or roof. If the fenestration area for new buildings or additions exceeds the maximum allowable, the area must be reduced proportionally along each exposure until the limit set in Section 5.5.4.2 is met. Fenestration U-factor and SHGC must be equal to the criteria from Tables 5.5-0 through 5.5-8 for the appropriate climate
• Skylights must be included in each thermal block when required by to meet the Minimum Skylight Fenestration Area
Exception:
When trade-offs are made between an addition and an existing building, the building envelope assumptions for the existing building in the budget building design must reflect existing conditions prior to any revisions that are part of this permit.
6. Lighting
Lighting power in the proposed design must be determined as follows:
• Where a complete lighting system exists, the actual lighting power for each thermal block must be used in the model
• Where a complete lighting system has been designed, lighting power for each thermal block must be determined in accordance with Installed Lighting Power and Interior and Exterior Luminaire Wattage requirements.
• Where no lighting exists or is specified, lighting power must be determined in accordance with the Building Area Method for the appropriate building area type
• Lighting system power must include all lighting system components shown or provided for on plans
• The lighting schedules in the proposed design must reflect the mandatory automatic lighting control requirements for Exterior Luminaire Wattage requirements.
• Automatic daylighting controls included in the proposed design may be modeled directly in the building simulation or through schedule adjustments
• Automatic lighting controls included in the proposed design but not required by Exterior Luminaire Wattage requirements must be modeled using standardized methods for occupancy sensors and other control factors
• Where a complete lighting system exists, lighting power in the budget building design must be the same as in the proposed design
• Where a lighting system has been designed, the interior lighting power allowance must be determined using either the Building Area Method or Space-by-Space Method with lighting power set equal to the maximum allowed. Additional interior lighting power for nonmandatory controls allowed under Additional Interior Lighting Power Using Nonmandatory Controls must not be included. Lighting power density in dwelling units must be 6.5 W/m²
• Where lighting neither exists nor is submitted with design documents, the lighting power in the budget building design must be the same as in the proposed design
• Power for fixtures not included in the lighting power calculation must be modeled identically
• Mandatory automatic lighting controls required by Exterior Luminaire Wattage requirements must be modeled the same as the proposed design
7. Thermal Blocks—HVAC Zones Designed
Where HVAC zones are defined on HVAC design drawings, each HVAC zone must be modeled 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 W/m² from the average
2. All HVAC zones in the thermal block that are adjacent to glazed 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.
8. Thermal Blocks—HVAC Zones Not Designed
Where the HVAC zones and systems have not yet been designed, thermal blocks must be defined based on similar internal load densities, occupancy, lighting, thermal and space temperature schedules, and in combination with the following:
• Separate thermal blocks must be assumed for interior and perimeter spaces (interior spaces are those located more than 4.6 m from an exterior wall)
• Separate thermal blocks must be assumed for spaces adjacent to glazed exterior walls; a separate zone must be provided for each orientation, except that orientations that differ by less than 45 degrees may be considered the same
• Separate thermal blocks must be assumed for spaces having floors in contact with ground or exposed to ambient conditions
• Separate thermal blocks must be assumed for spaces having exterior ceiling or roof assemblies
Same as proposed design.
9. Thermal Blocks—Multifamily Residential Buildings
Residential spaces must be modeled using at least one HVAC zone per dwelling unit except for those units with the same orientations, which may be combined into one thermal block. Corner units and units with roof or floor loads must only be combined with units sharing these features.
Same as proposed design.
10. HVAC Systems
The HVAC system type and all related performance parameters, such as equipment capacities and efficiencies, in the proposed design must be determined as follows:
• Where a complete HVAC system exists, the model must reflect the actual system type using actual component capacities and efficiencies
• Where an HVAC system has been designed, the HVAC model must be consistent with design documents. Mechanical equipment efficiencies must be adjusted from actual design conditions to the standard rating conditions specified in Section 6.4.1
• Where no heating system exists or has been specified, the heating system must be modeled as fossil fuel with characteristics identical to the budget building design
• Where no cooling system exists or has been specified, the cooling system must be modeled as an air-cooled single-zone system with characteristics identical to the budget building design
The HVAC system type and related performance parameters for the budget building design must be determined HVAC Systems, the system descriptions in Budget HVAC System Types and Budget HVAC System Specifications, and in accord with rules specified.
11. Service Water-Heating Systems
The service water-heating system type and all related performance parameters, such as equipment capacities and efficiencies, in the proposed design must be determined as follows:
• Where a complete service water-heating system exists, the model must reflect the actual system type using actual component capacities and efficiencies
• 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
• Where no service water-heating system exists or has been submitted with the design documents, no service water heating must be modeled<br><br>Piping losses must not be modeled.
The service water-heating system type in the budget building design must be identical to the proposed design. The service water-heating system performance of the budget building design must meet the requirements of Sections 7.4 and 7.5.
Exceptions:
1. If the service water-heating system type is not listed in Performance Requirements for Water-Heating Equipment—Minimum Efficiency Requirements, it must be determined based on Baseline Heating Method by Building Area Type
2. Where the 7.5 Prescriptive Compliance Path for Service Water Heating applies, the boiler must be split into a separate space-heating boiler and hot-water heater with efficiency requirements set to the least efficient allowed
3. For 24-hour facilities that meet the prescriptive criteria for use of condenser heat recovery systems described in Energy Recovery, such a system must be included in the baseline building design
Service water-heating energy consumption must be calculated explicitly based on the volume of service water heating required, the entering makeup water, and the leaving service water heating temperatures. Service water loads and use must be the same for both designs.
Piping losses must not be modeled.
12. Miscellaneous Loads
Receptacle, motor, and process loads must be modeled and estimated based on the building area type or space type category and must be assumed to be identical in the proposed and budget building designs. These loads must be included in simulations of the building and must be included when calculating the energy cost budget and design energy cost. All end-use load components within and associated with the building must be modeled, unless specifically excluded by Section 13 of Table 11.5.1, including but not limited to exhaust fans, parking garage ventilation fans, exterior building lighting, swimming pool heaters and pumps, elevators and escalators, and cooking equipment.
• Where power and other systems covered by Sections 8 and 10 have been designed and submitted with design documents, those systems must be determined in accordance with Sections 8 and 10
• 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
Same as proposed design.
13. Refrigeration
Where refrigeration equipment in the proposed design is rated in accordance with AHRI 1200, the rated energy use must be modeled. Otherwise, the proposed design must be modeled using the actual equipment capacities and efficiencies.
Where refrigeration equipment is specified in the proposed design and listed in Electrically Operated DX-DOAS Units, Single-Package and Remote Condenser, without Energy Recovery— Minimum Efficiency Requirements, the budget building design must be modeled as as specified using the actual equipment capacities.
If the refrigeration equipment is not listed above, the budget building design must be modeled the same as the proposed design.
14. Modeling Exceptions
All elements of the proposed design building envelope, HVAC, service water heating, lighting, and electrical systems must be modeled in the proposed design in accordance with the requirements of Modeling Requirements for Calculating Design Energy Cost and Energy Cost Budget.
Exceptions: Components and systems in the proposed design may be excluded from the simulation model provided that:
1. Component energy use does not affect the energy use of systems and components that are being considered for trade-off and
2. The applicable prescriptive requirements of Sections 5.5, 6.5, 7.5, and either 9.5 or 9.6 applying to the excluded components are met
None.
Energy used to recharge or refuel vehicles that are used for off-building site transportation purposes is not required to be modeled for the design energy cost or the energy cost budget.
This requirement establishes a standardized modeling framework that ensures consistent inputs and assumptions for both the proposed design and baseline building across all building systems and components, while excluding vehicle charging from the building's energy performance evaluation since transportation energy use is beyond the scope of building energy code compliance and would unfairly penalize buildings that support electric vehicle infrastructure.
HVAC Systems
The HVAC system type and related performance parameters for the budget building design must be determined from the figure below, the system descriptions in Table 11.5.2-1 and accompanying notes, and the following rules.
Budget HVAC System Types
1
VAV with parallel fan-powered boxes a
VAV d
Chilled water e
Electric resistance
2
VAV with reheat b
VAV d
Chilled water e
Hot-water fossil fuel boiler f
3
Packaged VAV with parallel fan-powered boxes a
VAV d
Direct expansion c
Electric resistance
4
Packaged VAV with reheat b
VAV d
Direct expansion c
Hot-water fossil fuel boiler f
5
Two-pipe fan coil
Single- or two-speed fan i,j
Chilled water e
Electric resistance
6
Water-source heat pump
Single- or two-speed fan i,j
Direct expansion c
Electric heat pump and boiler g
7
Four-pipe fan-coil
Single- or two-speed fan i,j
Chilled water e
Hot-water fossil fuel boiler f
8
Packaged terminal heat pump
Single-speed fan i
Direct expansion c
Electric heat pump h
9
Packaged rooftop heat pump
Single- or two-speed fan i,j
Direct expansion c
Electric heat pump h
10
Packaged terminal air conditioner
Single-speed fan i
Direct expansion
Hot-water fossil fuel boiler f
11
Packaged rooftop air conditioner
Single- or two-speed fan i,j
Direct expansion
Fossil fuel furnace
Budget HVAC System Specifications
a. VAV with Parallel Fan-Powered Boxes
Fans in parallel VAV fan-powered boxes shall be sized for 50% of the peak design flow rate and shall be modeled with 0.74 W per L/s fan power. Minimum volume set points for fan-powered boxes shall be equal to the minimum rate for the space required for ventilation consistent with Exception 1(b) to Section 6.5.2.1. Supply air temperature set point shall be constant at the design condition (see Section 11.5.2[g]).
b. VAV with Reheat
Minimum volume set points for VAV reheat boxes shall be the larger of the following: the minimum primary outdoor airflow rate required to meet the Simplified Procedure ventilation requirements of ASHRAE Standard 62.1 for the zone or the airflow rate required to comply with applicable codes or accreditation standards, including but not limited to pressure relationships or minimum air change rates. The supply air temperature for cooling shall be reset higher by 2.8°C under the minimum cooling load conditions.
c. Direct Expansion
The fuel type for the cooling system shall match that of the cooling system in the proposed design.
d. VAV
The supply, return, or relief fan motor shall be modeled assuming a variable-speed drive and shall meet the VAV fan part-load performance requirements of Section G3.1.3.15. If the proposed design's system has a DDC system at the zone level, static pressure set-point reset based on zone requirements in accordance with Section 6.5.3.2.3 shall be modeled.
e. Chilled Water
For systems using purchased chilled water, the chillers are not explicitly modeled, and chilled-water costs shall be based as determined in Section 11.4.3. Otherwise, the budget building design's chiller plant shall be modeled with chillers having the number as indicated in Table 11.5.2-2 as a function of budget building design chiller plant load and type as indicated in Table 11.5.2-3 as a function of individual chiller load. Where chiller fuel source is mixed, the system in the budget building design shall have chillers with the same fuel types and with capacities having the same proportional capacity as the proposed design's chillers for each fuel type.
Chilled-water supply temperature shall be modeled at 6.7°C design supply temperature and 13°C return temperature. Piping losses shall not be modeled in either building model. Chilled-water supply water temperature shall be reset in accordance with Section 6.5.4.4. Pump system power for each pumping system shall be the same as for the proposed design; if the proposed design has no chilled-water pumps, the budget building design pump power shall be 349 kW/1000 L/s (equal to a pump operating against a 23 m head, 65% combined impeller and motor efficiency).
The chilled-water system shall be modeled as primary-only variable flow with flow maintained at the design rate through each chiller using a bypass. Chilled-water pumps shall be modeled as riding the pump curve or with variable-speed drives when required in Section 6.5.4.2. The heat-rejection device shall be an open-circuit axial-fan cooling tower with variable-speed fan control, if required in Section 6.5.5, and shall meet the performance requirements of Table 6.8.1-7.
Condenser water design supply temperature shall be calculated using the cooling tower approach to the 0.4% evaporation design wet-bulb temperature as generated by the formula below, with a design temperature rise of 5.6°C:
Approach (5.6°C Range) = 10.02 – (0.24 × WB)
where WB is the 0.4% evaporation design wet-bulb temperature in °C, valid for wet bulbs from 12.8°C to 32.2°C.
Except during economizer operation, the tower shall be controlled to maintain a cooling tower leaving water temperature, where weather permits, per Table 11.5.2-5, floating up to the design leaving water temperature for the cooling tower. Pump system power for each pumping system shall be the same as the proposed design; if the proposed design has no condenser water pumps, the budget building design pump power shall be 301 kW/1000 L/s (equal to a pump operating against a 18 m head, 60% combined impeller and motor efficiency). Each chiller shall be modeled with separate condenser water and chilled-water pumps interlocked to operate with the associated chiller.
f. Fossil Fuel Boiler
For systems using purchased hot water or steam, the boilers are not explicitly modeled and hot-water or steam costs shall be based on actual utility rates. Otherwise, the boiler plant shall use the same fuel as the proposed design and shall be natural draft. The budget building design boiler plant shall be modeled with a single boiler if the budget building design plant load is 176 kW or less and with two equally sized boilers for plant capacities exceeding 176 kW. Boilers shall be staged as required by the load.
Hot-water supply temperature shall be modeled at 82°C design supply temperature and 54°C return temperature. Piping losses shall not be modeled in either building model. Hot-water supply water temperature shall be reset in accordance with Section 6.5.4.4. Pump system power for each pumping system shall be the same as for the proposed design; if the proposed design has no hot-water pumps, the budget building design pump power shall be 301 kW/1000 L/s (equal to a pump operating against a 18 m head, 60% combined impeller and motor efficiency). The hot-water system shall be modeled as primary-only with continuous variable flow. Hot-water pumps shall be modeled as riding the pump curve or with variable-speed drives when required by Section 6.5.4.2.
g. Electric Heat Pump and Boiler
Water-source heat pumps shall be connected to a common heat pump water loop controlled to maintain temperatures between 16°C and 32°C. Heat rejection from the loop shall be provided by a closed-circuit axial-fan evaporative fluid cooler with fan-speed control as required in Section 6.5.5.2. Heat addition to the loop shall be provided by a boiler that uses the same fuel as the proposed design and shall be natural draft. If no boilers exist in the proposed design, the budget building boilers shall be fossil fuel.
The budget building design boiler plant shall be modeled with a single boiler if the budget building design plant load is 176 kW or less and with two equally sized boilers for plant capacities exceeding 176 kW. Boilers shall be staged as required by the load. Piping losses shall not be modeled in either building model. Pump system power shall be the same as for the proposed design; if the proposed design has no pumps, the budget building design pump power shall be 349 kW/1000 L/s, which is equal to a pump operating against a 23 m head, with a 65% combined impeller and motor efficiency. Loop flow shall be variable with flow shutoff at each heat pump when its compressor cycles OFF as required by Section 6.5.4.5. Loop pumps shall be modeled as riding the pump curve or with variable-speed drives when required by Section 6.5.4.2.
h. Electric Heat Pump
Electric air-source heat pumps shall be modeled with electric auxiliary heat. The system shall be controlled with a multistage space thermostat and an outdoor air thermostat wired to energize auxiliary heat only on the last thermostat stage and when outdoor air temperature is less than 4°C.
i. Fan System Operation
Fans shall be controlled in the same manner as in the proposed design; i.e., fan operation whenever the space is occupied or fan operation cycled ON calls for heating and cooling.
j. Fan Speed Control
Fans shall operate as one or two speed as required by Section 6.5.3.2, regardless of the fan speed control used in the proposed design.
Budget Building Systems Not Listed
Components and parameters not listed above or otherwise specifically addressed in this subsection must be identical to those in the proposed design. However, where there are specific requirements in the HVAC - Prescriptive Compliance Path and HVAC Alternative Compliance Paths, the component efficiency in the budget building design must be adjusted to the lowest efficiency level allowed by the requirement for that component type.
This requirement establishes a systematic method for determining the baseline HVAC system configuration based on building characteristics, while ensuring that any HVAC components or parameters not explicitly defined in the standard tables are modeled identically in both designs to maintain consistency. The exception ensures that baseline equipment efficiencies reflect minimum code-compliant performance levels, preventing the baseline from being artificially inflated by using the proposed design's higher-efficiency equipment when prescriptive minimum efficiency requirements exist.
Performance Requirements for Water-Heating Equipment—Minimum Efficiency Requirements
Electric table-top water heaters
≤12 kW
≥76 L and ≤450 L, <309.75 W/L
For applications outside U.S., see footnote (h). For U.S. applications, see footnote (g).
Electric storage water heaters
≤12 kW
≥208 L and ≤309.75 W/L
For applications outside U.S., see footnote (h). For U.S. applications, see footnote (g).
>208 L and <454 L
For applications outside U.S., see footnote (h). For U.S. applications, see footnote (g).
>12 kW
<309.75 W/L
SL ≤ 0.3 + 27/Vm %/h
Electric instantaneous water heaters
≤12 kW
≥309.75 W/L, <7.6 L
For applications outside US, see footnote (h). For US applications, see footnote (g).
>12 kW and ≤58.6 kW
≥309.75 W/L, ≥7.6 L, ≤8.2°C
Very Small DP: UEF = 0.80<br>Low DP: UEF = 0.80<br>Medium DP: UEF = 0.80<br>High DP: UEF = 0.80
>58.6 kW
≥309.75 W/L, <38 L
No requirement
≥309.75 W/L, ≥38 L
No requirement
Gas storage water heaters
≤22 kW
<309.75 L, ≥75.7 L and ≤208 W/L
For applications outside U.S., see footnote (h). For U.S. applications, see footnote (g).
<208 L and ≤309.75 L
For applications outside U.S., see footnote (h). For U.S. applications, see footnote (g).
>22 kW and ≤31 kW
<309.75 W/L, ≤454 L, ≤82°C
Very Small DP: UEF = 0.2674 – (0.0009 × Vr)<br>Low DP: UEF = 0.5362 – (0.0012 × Vr)<br>Medium DP: UEF = 0.6002 – (0.0011 × Vr)<br>High DP: UEF = 0.6597 – (0.0009 × Vr)
>31 kW
<309.75 W/L
80% Et<br>SL ≤ (Q/800 + 0.0166 V), kW
Gas instantaneous water heaters
>14.6 kW and ≤58.6 kW
≥309.75 W/L, <7.57 L
For applications outside U.S., see footnote (h). For U.S. applications, see footnote (g).
>58.6 kW
≥309.75 W/L, <37.8 L
80% Et
>58.6 kW
≥309.75 W/L, ≥37.8 L
80% Et<br>SL ≤ (Q/800 + 0.0166 V), kW
Oil storage water heaters
≤30.8 kW
<309.75 W/L, <189 L
For applications outside U.S., see footnote (h). For U.S. applications, see footnote (g).
>30.8 kW and ≤41 kW
<309.75 W/L, <7.6 L, <82°C
Very Small DP: UEF = 0.2932 – (0.0015 × Vr)<br>Low DP: UEF = 0.5596 – (0.0018 × Vr)<br>Medium DP: UEF = 0.6194 – (0.0016 × Vr)<br>High DP: UEF = 0.6740 – (0.0013 × Vr)
>41 kW
<309.75 W/L
80% Et<br>SL ≤ (Q/800 + 0.0166 V), kW
Oil instantaneous water heaters
≤61 kW
≥309.75 W/L, <7.6 L
80% Et<br>EF ≥ 0.59 – 0.0005 × V
>61 kW
≥309.75 W/L, <37.85 L
80% Et
>61 kW
≥309.75 W/L, ≥37.85 L
78% Et<br>SL ≤ (Q/800 + 0.0166 V), kW
Hot-water supply boilers, gas and oil
≥88 kW and <3663 kW
≥309.75 W/L, <37.8 L
80% Et
Hot-water supply boilers, gas
≥88 kW and <3663 kW
≥309.75 W/L, ≥37.8 L
80% Et<br>SL ≤ (Q/800 + 0.0166 V), kW
Hot-water supply boilers, oil
≥88 kW and <3663 kW
≥309.75 W/L, ≥37.8 L
78% Et<br>SL ≤ (Q/800 + 0.0166 V), kW
Pool heaters, oil and gas
All
82% Et for commercial pool heaters and for applications outside U.S. For U.S. applications, see footnote (g).
Heat pump pool heaters
All
10°C db, 6.8°C wb outdoor air, 26.7°C entering water
4.0 COP
Unfired storage tanks
All
R-2.2
a. Thermal efficiency (Et) is a minimum requirement, while standby loss is a maximum requirement. In the standby loss equation, V is the rated volume in litres and Q is the nameplate input rate in kW. Standby loss for electric water heaters is in terms of %/h and denoted by the term "SL", and standby loss for gas and oil water heaters is in terms of kW and denoted by the term "SL." Vm is the measured volume in the tank in litres. Draw pattern (DP) refers to the water draw profile in the Uniform Energy Factor (UEF) test. UEF and Energy Factor (EF) are minimum requirements. In the UEF standard equations, Vr refers to the rated volume in litres.
b. Section 12 contains a complete specification, including the year version, of the referenced test procedure.
c. Electric instantaneous water heaters with input capacity >12 kW and ≤58.6 kW must comply with the requirements for >56 kW if the water heater either (1) has a storage volume >7.6 L; (2) is designed to provide outlet hot water at temperatures greater than 82°C; or (3) uses three-phase power.
d. Gas storage water heaters with input capacity >22 kW and ≤31 kW must comply with the requirements for the >30.7 kW if the water heater either (1) has a storage volume >454 L; (2) is designed to provide outlet hot water at temperatures greater than 82°C; or (3) uses three-phase power.
e. Oil storage water heaters with input capacity >31 kW and ≤41 kW must comply with the requirements for the >41 kW if the water heater either (1) has a storage volume >454 L; (2) is designed to provide outlet hot water at temperatures greater than 82°C; or (3) uses three-phase power.
f. Refer to Section 7.5.3 for additional requirements for gas storage and instantaneous water heaters and gas hot-water supply boilers.
g. Water heaters or gas pool heaters in this category or subcategory are regulated as consumer products by the USDOE as defined in 10 CFR 430.
h. Where this standard is being applied to a building outside the U.S. and Canada, and water heaters in this subcategory are being installed in that building, those water heaters shall meet the local efficiency requirements. If there are no local efficiency standards for residential water heaters, consideration should be given to using the USDOE efficiency requirements shown in Appendix F, Table F-2.
Baseline Heating Method by Building Area Type
Automotive facility
Gas storage water heater
Convenience store
Electric resistance water heater
Convention center
Electric resistance storage water heater
Courthouse
Electric resistance storage water heater
Dining: Bar lounge/leisure
Gas storage water heater
Dining: Cafeteria/fast food
Gas storage water heater
Dining: Family
Gas storage water heater
Dormitory
Gas storage water heater
Exercise center
Gas storage water heater
Fire station
Gas storage water heater
Grocery store
Gas storage water heater
Gymnasium
Gas storage water heater
Health-care clinic
Electric resistance storage water heater
Hospital and outpatient surgery center
Gas storage water heater
Hotel
Gas storage water heater
Library
Electric resistance storage water heater
Manufacturing facility
Gas storage water heater
Motel
Gas storage water heater
Motion picture theater
Electric resistance storage water heater
Multifamily
Gas storage water heater
Museum
Electric resistance storage water heater
Office
Electric resistance storage water heater
Parking garage
Electric resistance storage water heater
Penitentiary
Gas storage water heater
Performing arts theater
Gas storage water heater
Police station
Electric resistance storage water heater
Post office
Electric resistance storage water heater
Religious facility
Electric resistance storage water heater
Retail
Electric resistance storage water heater
School/university
Gas storage water heater
Sports arena
Gas storage water heater
Town hall
Electric resistance storage water heater
Transportation
Electric resistance storage water heater
Warehouse
Electric resistance storage water heater
Workshop
Electric resistance storage water heater
All others
Gas storage water heater
Supply Fan Energy in Certain Package Equipment
Where efficiency ratings include supply fan energy, the efficiency rating must be adjusted to remove the supply fan energy. For Budget System Types 3, 4, 6, 8, 9, 10, and 11 (above), calculate the minimum COPnfcooling and COPnfheating using the equation for the applicable performance rating as indicated in Tables 6.8.1-1 through 6.8.1-4.
Electrically Operated Unitary Air Conditioners and Condensing Units—Minimum Efficiency Requirements
Air conditioners, air cooled
<19 kW
All
Split system, three phase and applications outside U.S. single phase
3.81 SCOPC before 1/1/2023, 3.93 SCOP2C after 1/1/2023
All
Single-package, three phase and applications outside U.S. single phase
4.10 SCOPC before 1/1/2023, 3.93 SCOP2C after 1/1/2023
Space constrained, air cooled
≤9 kW
All
Split system, three phase and applications outside U.S. single phase
3.52 SCOPC before 1/1/2023, 3.43 SCOP2C after 1/1/2023
All
Single package, three phase and applications outside U.S. single phase
3.52 SCOPC before 1/1/2023, 3.43 SCOP2C after 1/1/2023
Small duct, high velocity, air cooled
<19 kW
All
Split system, three phase and applications outside U.S. single phase
3.52 SCOPC before 1/1/2023, 3.52 SCOP2C after 1/1/2023
Air conditioners, air cooled
≥19 kW and <40 kW
Electric resistance (or none)
Split system and single package
3.28 COPC, 3.78 ICOPC before 1/1/2023, 4.34 ICOPC after 1/1/2023
All other
3.22 COPC, 3.76 ICOPC before 1/1/2023, 4.28 ICOPC after 1/1/2023
≥40 kW and <70 kW
Electric resistance (or none)
3.22 COPC, 3.63 ICOPC before 1/1/2023, 4.16 ICOPC after 1/1/2023
All other
3.17 COPC, 3.58 ICOPC before 1/1/2023, 4.10 ICOPC after 1/1/2023
≥70 kW and <223 kW
Electric resistance (or none)
Split system and single package
2.93 COPC, 3.40 ICOPC before 1/1/2023, 3.87 ICOPC after 1/1/2023
All other
2.87 COPC, 3.34 ICOPC before 1/1/2023, 3.81 ICOPC after 1/1/2023
≥223 kW
Electric resistance (or none)
2.84 COPC, 3.28 ICOPC before 1/1/2023, 3.66 ICOPC after 1/1/2023
All other
2.78 COPC, 3.22 ICOPC before 1/1/2023, 3.60 ICOPC after 1/1/2023
Air conditioners, water cooled
<19 kW
All
Split system and single package
3.55 COPC, 3.60 ICOPC
≥19 kW and <40 kW
Electric resistance (or none)
3.55 COPC, 4.07 ICOPC
All other
3.49 COPC, 4.02 ICOPC
≥40 kW and <70 kW
Electric resistance (or none)
3.66 COPC, 4.07 ICOPC
All other
3.60 COPC, 4.02 ICOPC
≥70 kW and <223 kW
Electric resistance (or none)
3.63 COPC, 3.99 ICOPC
All other
3.58 COPC, 3.93 ICOPC
≥223 kW
Electric resistance (or none)
3.58 COPC, 3.96 ICOPC
All other
3.52 COPC, 3.90 ICOPC
Air conditioners, evaporatively cooled
<19 kW
All
Split system and single package
3.55 COPC, 3.60 ICOPC
≥19 kW and <40 kW
Electric resistance (or none)
3.55 COPC, 3.60 ICOPC
All other
3.49 COPC, 3.55 ICOPC
≥40 kW and <70 kW
Electric resistance (or none)
3.52 COPC, 3.58 ICOPC
All other
3.46 COPC, 3.52 ICOPC
≥70 kW and <223 kW
Electric resistance (or none)
3.49 COPC, 3.55 ICOPC
All other
3.43 COPC, 3.49 ICOPC
≥223 kW
Electric resistance (or none)
3.43 COPC, 3.49 ICOPC
All other
3.37 COPC, 3.43 ICOPC
Condensing units, air cooled
≥40 kW
3.08 COPC, 3.46 ICOPC
Condensing units, water cooled
≥40 kW
3.96 COPC, 4.10 ICOPC
Condensing units, evaporatively cooled
≥40 kW
3.96 COPC, 4.10 ICOPC
Electrically Operated Air-Cooled Unitary Heat Pumps—Minimum Efficiency Requirements
Air cooled (cooling mode)
<19 kW
All
Split system, three phase and applications outside U.S. single phase b
4.10 SCOPC
before 1/1/2023
4.19 SCOP2C
after 1/1/2023
Single package, three phase and applications outside U.S. single phase b
4.10 SCOPC
before 1/1/2023
3.93 SCOP2C
after 1/1/2023
All
Split system, three phase and applications outside U.S. single phase b
4.10 SCOPC
before 1/1/2023
4.19 SCOP2C
after 1/1/2023
Space constrained, air cooled
(cooling mode)
£9 kW
All
Split system, three phase and applications outside U.S. single phase b
3.52 SCOPC
before 1/1/2023
3.42 SCOP2C
after 1/1/2023
Single package, three phase and applications outside U.S. single phase b
3.52 SCOPC
before 1/1/2023
3.42 SCOP2Cafter 1/1/2023
Small duct, high velocity, air cooled (cooling mode)
<19 kW
All
Split System, three phase and applications outside U.S. single phase b
4.10 SCOPC
before 1/1/2023
4.10 SCOP2C
after 1/1/2023
Air cooled (cooling mode)
³19 kW and
<40 kW
Electric resistance (or none)
Split system and single package
3.22 COPC
3.58 ICOPC
before 1/1/2023
4.13 ICOPC
after 1/1/2023
All other
3.17 COPC
3.52 ICOPC
before 1/1/2023
4.07 ICOPC
after 1/1/2023
³40 kW and
<70 kW
Electric resistance (or none)
3.11 COPC
3.40 ICOPC
before 1/1/2023
3.96 ICOPC
after 1/1/2023
All other
3.05 COPC
3.34 ICOPC
before 1/1/2023
3.90 ICOPC
after 1/1/2023
³70 kW
Electric resistance (or none)
2.78 COPC
3.11 ICOPC
before 1/1/2023
3.66 ICOPC
after 1/1/2023
All other
2.73 COPC
3.05 ICOPC
before 1/1/2023
3.60 ICOPC
after 1/1/2023
a. Section 12 contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.
b. Single-phase, U.S. air-cooled heat pumps <19 kW are regulated as consumer products by the U.S. Department of Energy Code of Federal Regulations 10 CFR
430. SCOPC, SCOP2C and SCOPH, and SCOP2H values for single-phase products are set by the U.S. Department of Energy.
Informative Note: See Informative Appendix F for the U.S. Department of Energy minimum.
Water-Chilling Packages—Minimum Efficiency Requirements
Air-cooled chillers
<528 kW
COP (W/W)
≥2.985 FL<br>≥4.048 IPLV.SI
≥2.866 FL<br>≥4.669 IPLV.SI
≥528 kW
≥2.985 FL<br>≥4.137 IPLV.SI
≥2.866 FL<br>≥4.758 IPLV.SI
Air-cooled without condenser, electrically operated
All capacities
COP (W/W)
Air-cooled chillers without condenser must be rated with matching condensers and comply with air-cooled chiller efficiency requirements
Water-cooled, electrically operated positive displacement
<264 kW
COP (W/W)
≥4.694 FL<br>≥5.867 IPLV.SI
≥4.513 FL<br>≥7.041 IPLV.SI
≥264 kW and <528 kW
≥4.889 FL<br>≥6.286 IPLV.SI
≥4.694 FL<br>≥7.184 IPLV.SI
≥528 kW and <1055 kW
≥5.334 FL<br>≥6.519 IPLV.SI
≥5.177 FL<br>≥8.001 IPLV.SI
≥1055 kW and <2110 kW
≥5.771 FL<br>≥6.770 IPLV.SI
≥5.633 FL<br>≥8.586 IPLV.SI
≥2100 kW
≥6.286 FL<br>≥7.041 IPLV.SI
≥6.018 FL<br>≥9.264 IPLV.SI
Water-cooled, electrically operated centrifugal
<528 kW
COP (W/W)
≥5.771 FL<br>≥6.401 IPLV.SI
≥5.065 FL<br>≥8.001 IPLV.SI
≥528 kW and <1055 kW
≥5.771 FL<br>≥6.401 IPLV.SI
≥5.544 FL<br>≥8.801 IPLV.SI
≥1055 kW and <1407 kW
≥6.286 FL<br>≥6.770 IPLV.SI
≥5.917 FL<br>≥9.027 IPLV.SI
≥1407 kW and <2110 kW
≥6.286 FL<br>≥7.041 IPLV.SI
≥6.018 FL<br>≥9.264 IPLV.SI
≥2110 kW
≥6.286 FL<br>≥7.041 IPLV.SI
≥6.018 FL<br>≥9.264 IPLV.SI
Air-cooled absorption, single effect
All capacities
COP (W/W)
≥0.600 FL
NA
Water-cooled absorption, single effect
All capacities
COP (W/W)
≥0.700 FL
NA
Absorption double effect, indirect fired
All capacities
COP (W/W)
≥1.000 FL<br>≥1.050 IPLV.SI
NA
Absorption double effect, direct fired
All capacities
COP (W/W)
≥1.000 FL<br>≥1.000 IPLV.SI
NA
Electrically Operated Packaged Terminal Air Conditioners, Packaged Terminal Heat Pumps, Single-Package Vertical Air Conditioners, Single-Package Vertical Heat Pumps, Room Air Conditioners, and Room Air-Conditioner Heat Pumps—Minimum Efficiency Requirements
Equipment Type
Size Category (Input)
Subcategory or Rating Condition
Minimum Efficiency d
PTAC (cooling mode) standard size
<2.1 kW
35°C db/23.9°C wb
outdoor airc
3.49 COPC
³2.1 kW and
£4.4 kW
4.10 – (0.300 × Cap) COPC e
>4.4 kW
2.78 COPC
PTAC (cooling mode) nonstandard size a
<2.1 kW
35°C db/23.9°C wb
outdoor airc
2.75 COPC
³2.1 kW and
£4.4 kW
3.19 – (0.213 × Cap) COPC e
>4.4 kW
2.26 COPC
PTHP (cooling mode) standard size
<2.1 kW
35°C db/23.9°C wb
outdoor airc
3.49 COPC
³2.1 kW and
£4.4 kW
4.10 – (0.300 × Cap) COPC e
>4.4 kW
2.78 COPC
PTHP (cooling mode) nonstandard size b
<2.1 kW
35°C db/23.9°C wb
outdoor airc
2.73 COPC
³2.1 kW and
£4.4 kW
3.17 – (0.213 × Cap) COPC e
>4.4 kW
2.23 COPC
PTHP (heating mode) standard size
<2.1 kW
8.3°C db/6.1°C wb
outdoor air
3.3 COPH
³2.1 kW and
£4.4 kW
3.7 – (0.177 × Cap) COPH e
>4.4 kW
2.9 COPH
PTHP (heating mode) nonstandard size b
<2.1 kW
8.3°C db/6.1°C wb
outdoor air
2.7 COPH
³2.1 kW and
£4.4 kW
2.9 – (0.089 × Cap) COPH e
>4.4 kW
2.5 COPH
SPVAC (cooling mode) single and three phase
<19 kW
35°C db/23.9°C wb
outdoor airc
3.22 COPC
³19 kW and
<40 kW
2.93 COPC
³40 kW
and <70 kW
2.93 COPC
SPVHP (cooling mode)
<19 kW
35°C db/23.9°C wb
outdoor airc
3.22 COPC
³19 kW and
<40 kW
2.93 COPC
³40 kW
and <70 kW
2.93 COPC
SPVHP (heating mode)
<19 kW
8.3°C db/6.1°C wb
outdoor air
3.3 COPH
³19 kW and
<40 kW
3.0 COPH
³40 kW
and <70 kW
3.0 COPH
a. Section 12 contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.
b. Nonstandard size units must be factory labeled as follows: “MANUFACTURED FOR NONSTANDARD SIZE APPLICATIONS ONLY; NOT TO BE INSTALLED IN NEW STANDARD PROJECTS.” Nonstandard size efficiencies apply only to units being installed in existing sleeves having an external wall opening of less than 0.45 m high or less than 1.0 m wide and having a cross-sectional area less than 0.4 m2.
c. The cooling mode wet-bulb temperature requirement only applies for units that reject condensate to the condenser coil.
d. Room air conditioners are regulated as consumer products by 10 CFR 430. For U.S. applications of room air conditioners, refer to Appendix F, Table F-3 for USDOE minimum efficiency requirements.
e. “Cap” in COPC and COPH equations for PTACs and PTHPs means “cooling capacity” in kW at 35°C outdoor dry-bulb temperature.
6 Heating, Ventilating, and Air Conditioning
Table 6.8.1-4 Electrically Operated Packaged Terminal Air Conditioners, Packaged Terminal Heat Pumps, Single-Package Vertical Air Conditioners, Single-Package Vertical Heat Pumps, Room Air Conditioners, and Room Air-Conditioner Heat Pumps—Minimum Efficiency Requirements (Continued)
a. Section 12 contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.
b. Nonstandard size units must be factory labeled as follows: “MANUFACTURED FOR NONSTANDARD SIZE APPLICATIONS ONLY; NOT TO BE INSTALLED IN NEW STANDARD PROJECTS.” Nonstandard size efficiencies apply only to units being installed in existing sleeves having an external wall opening of less than 0.45 m high or less than 1.0 m wide and having a cross-sectional area less than 0.4 m2.
c. The cooling mode wet-bulb temperature requirement only applies for units that reject condensate to the condenser coil.
d. Room air conditioners are regulated as consumer products by 10 CFR 430. For U.S. applications of room air conditioners, refer to Appendix F, Table F-3 for USDOE minimum efficiency requirements.
e. “Cap” in COPC and COPH equations for PTACs and PTHPs means “cooling capacity” in kW at 35°C outdoor dry-bulb temperature.
Electrically Operated Packaged Terminal Air Conditioners, Packaged Terminal Heat Pumps, Single-Package Vertical Air Conditioners, Single-Package Vertical Heat Pumps, Room Air Conditioners, and Room Air Conditioner Heat Pumps— Minimum Efficiency Requirements
Where multiple HVAC zones are combined into a single thermal block, the efficiencies for budget System Types 6, 8, and 10 taken from Tables 6.8.1-1 through 6.8.1-4 must be based on 2.6 kW equipment capacity for residential spaces; otherwise, it must be based on the capacity of the thermal block divided by the number of HVAC zones. Budget System Types 3, 4, 9, and 11 efficiencies taken from Tables 6.8.1-1 through 6.8.1-4 must be based on the cooling equipment capacity of a single floor when grouping identical floors.
Where a full- and part-load efficiency rating is provided in Tables 6.8.1-1 through 6.8.1-4, the following full-load equations must be used:
COPnfcooling = 9.13E-4 × COPC × Q + 1.15 × COPC
COPnfcooling = –0.0885 × SCOPC² + 1.295 × SCOPC (applies to cooling efficiency only)
COPnfheating = 5.05E-4 × COPH8.3 × Q + 1.062 × COPH8.3 (applies to Systems 6 and 9 heating efficiency only)
COPnfheating = –0.3446 × SCOPH² + 2.434 × SCOPH
COPnfcooling = 1.1338 × COP – 0.2145 (applies to Systems 8 and 10 cooling efficiency only)
COPnfheating = 1.1329 × COP – 0.214 (applies to System 8 heating efficiency only)
Where COPnfcooling and COPnfheating are the packaged HVAC equipment cooling and heating energy efficiency, respectively, to be used in the budget building design, which excludes supply fan power, and Q is the AHRI-rated cooling capacity in kW. If Q is greater than 223 kW, use 223 kW in the calculation. COPC, SCOPC, SCOPH8.3, and SCOPH must be at AHRI test conditions. Fan energy must be modeled separately according to Section 11.5.2(h). Supply and return/relief system fans must be modeled as operating at least whenever the spaces served are occupied, except as specifically noted in Table 11.5.2-1.
This requirement ensures accurate baseline energy modeling by separating supply fan energy from packaged equipment efficiency ratings, allowing fan energy to be calculated independently based on actual system design characteristics. The equations and capacity-based rules provide standardized methods for converting manufacturer ratings to simulation inputs while accounting for system size variations and preventing unrealistic baseline assumptions when multiple zones are grouped or identical floors are modeled together.
Minimum Outdoor Air Ventilation Rate
Minimum outdoor air ventilation rates must be the same for both the budget building design and proposed design. Exhaust air heat recovery must be modeled for the budget building design in accordance with Section 6.5.6.1.
However, when modeling demand control ventilation in the proposed design for spaces where demand control ventilation is not required per Section 6.4.3.8, or where the minimum outdoor air intake flow in the proposed design is provided in excess of the amount required by Section 6.5.3.7, the baseline building design must be modeled to reflect the minimum amount required by Section 6.5.3.7.
This requirement ensures consistent ventilation assumptions between the proposed and baseline designs to prevent unfair advantages or penalties based solely on outdoor air quantities, while allowing credit for demand control ventilation when it exceeds mandatory requirements and preventing the baseline from being penalized when the proposed design voluntarily provides excess ventilation beyond code minimums, thus encouraging both ventilation innovation and energy-efficient ventilation strategies.
Electrically Operated DX-DOAS Units, Single-Package and Remote Condenser, without Energy Recovery—Minimum Efficiency Requirements
Air cooled (dehumidification mode)
1.8 ISMRE
Air source heat pumps (dehumidification mode)
1.8 ISMRE
Water cooled (dehumidification mode)
Cooling tower condenser water
2.2 ISMRE
Chilled Water
2.7 ISMRE
Air source heat pump (heating mode)
1.2 ISCOP
Water source heat pump (dehumidification mode)
Ground source, closed loop
2.2 ISMRE
Ground-water source
2.3 ISMRE
Water source
1.8 ISMRE
Water source heat pump (heating mode)
Ground source, closed loop
2.0 ISCOP
Ground-water source
3.2 ISCOP
Water source
3.5 ISCOP
Economizers
Budget building systems as listed in Table 11.5.2-1 must have air economizers or fluid economizers, the same as in the proposed design, in accordance with Section 6.5.1. The high-limit shutoff must be in accordance with Table 11.5.2-4.
This requirement ensures that the baseline building receives credit for economizer capabilities when they are included in the proposed design, preventing scenarios where economizer benefits would be lost in the comparison and encouraging the use of free cooling strategies where climate conditions are favorable.
Preheat Coils
If the proposed design system has a preheat coil, the budget building design's system must be modeled with a preheat coil controlled in the same manner.
This requirement ensures consistent cold climate performance assumptions between the proposed and baseline designs by requiring the same preheat strategy in both models, preventing unfair comparison when preheat is necessary for proper system operation or freeze protection.
Supply Airflow Rates
System design supply air rates for the budget building design must be based on a supply-air-to-room temperature set-point difference of 11°C or the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards, whichever is greater.
For systems with multiple zone thermostat set points, use the design set point that will result in the lowest supply air cooling set point or highest supply air heating set point. If return or relief fans are specified in the proposed design, the budget building design must also be modeled with fans serving the same functions and sized for the budget system supply fan air quantity less the minimum outdoor air, or 90% of the supply fan air quantity, whichever is larger.
For systems serving laboratory spaces, airflow rate must be based on a supply-air-to-room temperature set-point difference of 9°C or the required ventilation air or makeup air, whichever is greater. If the proposed design HVAC system airflow rate based on latent loads is greater than the design airflow rate based on sensible loads, then the same supply-air-to-room-air humidity ratio difference used to calculate the proposed design airflow must be used to calculate design airflow rates for the budget building design.
This requirement establishes standardized airflow sizing criteria for the baseline building based on typical design practice (11°C temperature difference), while accommodating special cases such as laboratory spaces with high ventilation requirements and humid climates where latent loads dominate, ensuring that baseline system sizing is reasonable and comparable to the proposed design's actual operating requirements without penalizing necessary airflow rates driven by code, health, or moisture control needs.
Fan System Efficiency
Fan system efficiency (input kW per L/s of supply air, including the effect of belt losses but excluding motor and motor drive losses) must be the same as the proposed design or up to the limit prescribed in Section 6.5.3.1, whichever is smaller. If this limit is reached, each fan must be proportionally reduced in input kW until the limit is met. Fan electrical power must then be determined by adjusting the calculated fan kW by the minimum motor efficiency prescribed by Section 10.4.1 for the appropriate motor size for
This requirement allows the baseline building to benefit from the proposed design's efficient fan system design while capping the baseline fan efficiency at code-prescribed maximum power levels, ensuring that extremely efficient proposed designs still demonstrate savings compared to a reasonable baseline and preventing unrealistic baseline assumptions that would penalize good fan system design by requiring identical modeling without efficiency limits.
Equipment Capacities
The equipment capacities for the budget building design must be sized proportionally to the capacities in the proposed design based on sizing runs, meaning the ratio between the capacities used in the annual simulations and the capacities determined by the sizing runs must be the same for both the proposed design and budget building design. Unmet load hours for the proposed design or baseline building designs must not exceed 300 hours (of the 8760 hours simulated). The unmet load hours for the proposed design must not exceed the unmet load hours for the budget building design.
Alternatively, unmet load hours exceeding these limits may be approved by the building official, provided that sufficient justification is given indicating that the accuracy of the simulation is not significantly compromised by these unmet loads.
This requirement ensures that both the proposed and baseline buildings are modeled with appropriately sized equipment using consistent sizing methodologies, preventing unfair advantages from oversized or undersized equipment assumptions. The unmet load hour limits ensure that both models adequately serve the building's heating and cooling needs throughout the year, maintaining simulation accuracy while allowing flexibility for approved exceptions when unusual conditions or design strategies result in acceptable performance despite higher unmet hours.
Determining the HVAC System
Each HVAC system in a proposed design is mapped on a one-to-one correspondence with one of eleven HVAC systems in the budget building design. To determine the budget building system, follow these steps:
Step 1
Enter Figure 11.5.2 at "Water" if the proposed design system condenser is water or evaporatively cooled; enter at "Air/None" if the condenser is air cooled. Closed-circuit dry coolers are considered air cooled. Systems utilizing district cooling are treated as if the condenser water type were "water." If no mechanical cooling is specified or the mechanical cooling system in the proposed design does not require heat rejection, the system is treated as if the condenser water type were "Air." For proposed designs with ground-source or groundwater-source heat pumps, the budget system must be water-source heat pump (System 6).
Step 2
Select the path that corresponds to the proposed design heat source: electric resistance, heat pump (including air source and water source), or fuel-fired. Systems utilizing district heating (steam or hot water) are treated as if the heating system type were "Fossil Fuel." Systems with no heating capability are treated as if the heating system type were "Fossil Fuel." For systems with mixed fuel heating sources, the system or systems that use the secondary heating source type (the one with the smallest total installed output capacity for the spaces served by the system) must be modeled identically in the budget building design, and the primary heating source type must be used in Figure 11.5.2 to determine budget system type.
Step 3
Select the budget building design system category. The system under "Single-Zone Residential System" must be selected if the HVAC system in the proposed design is a single-zone system and serves a residential space. The system under "Single-Zone Nonresidential System" must be selected if the HVAC system in the proposed design is a single-zone system and serves other than residential spaces. The system under "All Other" must be selected for all other cases.
This requirement provides a systematic methodology for mapping any proposed HVAC system configuration to one of eleven standardized baseline system types based on cooling source, heating source, and system configuration, ensuring consistent and fair baseline comparisons regardless of the complexity or uniqueness of the proposed design while accounting for the fundamental performance characteristics that most significantly impact energy use.
Kitchen Exhaust
For kitchens with a total exhaust hood airflow rate greater than 2400 L/s, use a demand ventilation system on 75% of the exhaust air. The system must reduce exhaust and replacement air system airflow rates by 50% for one half of the kitchen occupied hours in the baseline building design. If the proposed design uses demand ventilation, the same airflow rate schedule must be used. The maximum exhaust flow rate allowed for the hood or hood section must meet the requirements of Section 6.5.7.2.2 for the numbers and types of hoods and appliances provided in the proposed design.
This requirement recognizes that large commercial kitchens benefit significantly from demand ventilation strategies and establishes a baseline that includes partial demand control for kitchens above a certain size threshold, while ensuring hood exhaust rates are appropriate for the cooking equipment specified and preventing excessive exhaust rates that would unnecessarily increase energy consumption for conditioning makeup air.
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