When the building permit being sought applies to less than the whole building, only the calculation parameters related to the systems to which the permit applies shall be allowed to vary. Parameters relating to unmodified existing conditions or to future building components shall be identical for both the energy cost budget and the design energy cost calculations. Future building components shall meet the prescriptive requirements of Sections 5.5, 6.5, 7.5, and either 9.5 or 9.6.
Compliance with Section 11 will be achieved if
- all requirements of Sections 5.4, 6.4, 7.4, 8.4, 9.4, and 10.4 are met;
- the design energy cost, as calculated in Section 11.5, does not exceed the energy cost budget as calculated by the simulation program described in Section 11.4; and
- the energy efficiency level of components specified in the building design meet or exceed the efficiency levels used to calculate the design energy cost.
The simulation program shall be approved by the adopting authority and shall, at a minimum, have the ability to explicitly model all of the following:
- A minimum of 1400 hours per year.
- 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.
- Ten or more thermal zones.
- Part-load performance curves for mechanical equipment.
- Capacity and efficiency correction curves for mechanical heating and mechanical cooling equipment.
- Air-side economizer and fluid economizer with integrated control.
- The budget building design characteristics specified in Section 11.4.5.
The simulation program shall perform the simulation using hourly values of climatic data, such as temperature and humidity from representative climatic data, for the city in which the proposed design is to be located. For cities or urban regions with several climatic data entries, and for locations where weather data are not available, the designer shall select available weather data that best represent the climate at the construction site. Such selected weather data shall be approved by the authority having jurisdiction.
Site-recovered energy shall not be considered purchased energy and shall be subtracted from the proposed design energy consumption prior to calculating the design energy cost. On-site renewable energy, generated by systems included on the building permit, and used directly by the building shall be subtracted from the proposed design energy consumption prior to calculating the design energy cost. The reduction in design energy cost associated with on-site renewable energy shall be no more than 5% of the calculated energy cost budget.
The design energy cost and energy cost budget shall 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 shall be based on the energy source used as the backup energy source, or electricity if no backup energy source has been specified.
Where no simulation program is available that adequately models a design, material, or device, the authority having jurisdiction may approve an exceptional calculation method to be used to demonstrate compliance with Section 11. Applications for approval of an exceptional method to include theoretical and empirical information verifying the method's accuracy shall include documentation to demonstrate that the exceptional calculation method and results
- make no change in any input parameter values specified by this standard and the adopting authority,
- provide input and output documentation that facilitates the enforcement agency's review and meets the formatting and content required by the adopting authority, and
- are supported with instructions for using the method to demonstrate that the energy cost budget and design energy cost required by Section 11 are met.
The simulation model for calculating the design energy cost and the energy cost budget shall be developed in accordance with the requirements in Table 11.5.1.
|Proposed Design (Column A)
Design Energy Cost (DEC)
|Budget Building Design (Column B)
Energy Cost Budget (ECB)
|1. Design Model|
||The budget building design shall be developed by modifying the proposed design as described in this table. Except as specifically instructed in this table, all building systems and equipment shall 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:
||Same as proposed design.|
|3. Space Use Classification|
|The building area type or space type classifications shall be chosen in accordance with Section 9.5.1 or 9.6.1. The user or designer shall specify the space use classifications using either the building area type or space type categories but shall 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.||Same as proposed design.|
|The schedule types listed in Section 126.96.36.199(b) shall be required input. The schedules shall be typical of the proposed design as determined by the designer and approved by the authority having jurisdiction. Required schedules shall be identical for the proposed design and budget building design.||Same as proposed design.|
|5. Building Envelope|
|All components of the building envelope in the proposed design shall be modeled as shown on architectural drawings or as installed for existing building envelopes.
Exceptions: The following building elements are permitted to differ from architectural drawings.
|The budget building design shall have identical conditioned floor area and identical exterior dimensions and orientations as the proposed design, except as follows:
Exceptions: When trade-offs are made between an addition and an existing building, as described in the exception to Section 188.8.131.52, the building envelope assumptions for the existing building in the budget building design shall reflect existing conditions prior to any revisions that are part of this permit.
|Lighting power in the proposed design shall be determined as follows:
|7. Thermal Blocks— HVAC Zones Designed|
|Where HVAC zones are defined on HVAC design drawings, each HVAC zone shall 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 all of the following conditions are met:
|Same as proposed design.|
|8. Thermal Blocks—HVAC Zones Not Designed|
|Where the HVAC zones and systems have not yet been designed, thermal blocks shall be defined based on similar internal load densities, occupancy, lighting, thermal and space temperature schedules, and in combination with the following:
||Same as proposed design.|
|9. Thermal Blocks—Multifamily Residential Buildings|
|Residential spaces shall be modeled using one thermal block per space except that those facing the same orientations may be combined into one thermal block. Corner units and units with roof or floor loads shall 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 shall be determined as follows:
||The HVAC system type and related performance parameters for the budget building design shall be determined from Figure 11.5.2, the system descriptions in Table 11.5.2-1 and accompanying notes, and in accord with rules specified in Section 11.5.2(a) through 11.5.2(k).|
|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 shall be determined as follows:
||The service water-heating system type in the budget building design shall be identical to the proposed design. The service water-heating system performance of the budget building design shall meet the requirements of Table 7.8.
|12. Miscellaneous Loads|
|Receptacle, motor, and process loads shall be modeled and estimated based on the building area type or space type category and shall be assumed to be identical in the proposed and budget building designs. These loads shall be included in simulations of the building and shall be included when calculating the energy cost budget and design energy cost. All end-use load components within and associated with the building shall be modeled, unless specifically excluded by Sections 13 and 14 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, refrigeration equipment, and cooking equipment.||Receptacle, motor, and process loads shall be modeled and estimated based on the building area type or space type category and shall be assumed to be identical in the proposed design and budget building design. These loads shall be included in simulations of the building and shall be included when calculating the energy cost budget and design energy cost. All end-use load components within and associated with the building shall be modeled, unless specifically excluded by Sections 13 and 14 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, refrigeration equipment, and cooking equipment.|
|13. Modeling Exceptions|
|All elements of the proposed design building envelope, HVAC, service water heating, lighting, and electrical systems shall be modeled in the proposed design in accordance with the requirements of Sections 1 throuah 12 of Table 11.5.1.
Exceptions: Components and systems in the proposed design may be excluded from the simulation model provided that
|14. Modeling Limitations to the Simulation Program|
|If the simulation program cannot model a component or system included in the proposed design, one of the following methods shall be used with the approval of the authority having jurisdiction:
||Same as proposed design.|
The HVAC system type and related performance parameters for the budget building design shall be determined from Figure 11.5.2, the system descriptions in Table 11.5.2-1 and accompanying notes, and the following rules:
- Budget Building Systems Not Listed. Components and parameters not listed in Figure 11.5.2 and Table 11.5.2-1 or otherwise specifically addressed in this subsection shall be identical to those in the proposed design.
- Minimum Equipment Efficiency. All HVAC and service water-heating equipment in the budget building design shall be modeled at the minimum efficiency levels, both part load and full load, in accordance with Sections 6.4 and 7.4. Chillers shall use Path A efficiencies as shown in Table 6.8.1-3.
- Supply Fan Energy in Certain Package Equipment. Where efficiency ratings include supply fan energy, the efficiency rating shall be adjusted to remove the supply fan energy. For Budget System Types 3, 4, 6, 9, and 11, 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. Where a full- and part-load efficiency rating is provided in Tables 6.8.1-1 through 6.8.1-4. the full-load equation below shall be used:
COPnfheating = 1.48E-7 × COP47 × Q + 1.062 × COP47where 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 AHRl-rated cooling capacity in Btu/h.
- Minimum Outdoor Air Ventilation Rate. Minimum outdoor air ventilation rates shall be the same for both the budget building design and proposed design. Exhaust air heat recovery shall be modeled for the budget building design in accordance with Section 184.108.40.206.
- Economizers. Budget building systems as listed in Table 11.5.2-1 shall have air economizers ox fluid economizers, the same as in the proposed design, in accordance with Section 6.5.1. The high-limit shutoff shall be in accordance with Table 11.5.2-4.
- Preheat Coils. If the proposed design system has a preheat coil, the budget building design's system shall be modeled with a preheat coil controlled in the same manner.
- Supply Airflow Rates. System design supply air rates for the budget building design shall be based on a supply-air-to-room-air temperature difference of 20°F. If return or relief fans are specified in the proposed design, the budget building design shall also be modeled with the same fan type 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.
- Fan System Efficiency. Fan system efficiency (bhp per cfm of supply air, including the effect of belt losses but excluding motor and motor drive losses) shall be the same as the proposed design or up to the limit prescribed in Section 220.127.116.11, whichever is smaller. If this limit is reached, each fan shall be proportionally reduced in brake horsepower until the limit is met. Fan electrical power shall then be determined by adjusting the calculated fan hp by the minimum motor efficiency prescribed by Section 10.4.1 for the appropriate motor size for each fan.
- Equipment Capacities. The equipment capacities for the budget building design shall be sized proportionally to the capacities in the proposed design based on sizing runs, i.e., the ratio between the capacities used in the annual simulations and the capacities determined by the sizing runs shall be the same for both the proposed design and budget building design. Unmet load hours for the proposed design or baseline building designs shall not exceed 300 hours. The unmet load hours for the proposed design shall 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.
- 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, do the following:
- Enter Figure 11.5.2 at "Water" if the proposed design system condenser is water or evaporatively cooled; enter Figure 11.5.2 at "Air/None" if the condenser is air cooled. Closed-circuit dry coolers shall be considered air cooled. Systems utilizing district cooling shall be 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 shall be treated as if the condenser water type were "Air." For proposed designs with ground-source or groundwater-source heat pumps, the budget system shall be water-source heat pump (System 6).
- 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) shall be treated as if the heating system type were "Fossil Fuel." Systems with no heating capability shall be 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) shall be modeled identically in the budget building design, and the primary heating source type shall be used in Figure 11.5.2 to determine budget system type.
- Select the budget building design system category. The system under "Single-Zone Residential System" shall 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" shall 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" shall be selected for all other cases.
- Kitchen Exhaust. For kitchens with a total exhaust hood airflow rate greater than 5000 cfm, use a demand ventilation system on 75% of the exhaust air. The system shall 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 shall be used. The maximum exhaust flow rate allowed for the hood or hood section shall meet the requirements of Section 18.104.22.168.2 for the numbers and types of hoods and appliances provided in the proposed design.
Figure 11.5.2 HVAC systems map.
Table 11.5.2-1 Budget System Descriptions
|System No.||System Type||Fan Control||Cooling Type||Heating Type|
|1||VAV with parallel fan-powered boxesa||VAVd||Chilled watere||Electric resistance|
|2||VAV with reheatb||VAVd||Chilled watere||Hot-water fossil fuel boilerf|
|3||Packaged VAV with parallel fan-powered boxesa||VAVd||Direct expansionc||Electric resistance|
|4||Packaged VAV with reheatb||VAVd||Direct expansionc||Hot-water fossil fuel boilerf|
|5||Two-pipe fan-coil||Single- or two-speed fani,j||Chilled watere||Electric resistance|
|6||Water-source heat pump||Single- or two-speed fani,j||Direct expansionc||Electric heat pump and boilerg|
|7||Four-pipe fan-coil||Single- or two-speed fani,j||Chilled watere||Hot-water fossil fuel boilerf|
|8||Packaged terminal heat pump||Single-speed fani||Direct expansionc||Electric heat pumph|
|9||Packaged rooftop heat pump||Single- or two-speed fani,j||Direct expansionc||Electric heat pumph|
|10||Packaged terminal air conditioner||Single-speed fani||Direct expansion||Hot-water fossil fuel boilerf|
|11||Packaged rooftop air conditioner||Single- or two-speed fani,j||Direct expansion||Fossil fuel furnace|
- 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 0.35 W/cfm fan power. Minimum volume sef 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 22.214.171.124. Supply air temperature set point shall be constant at the design condition (see Section 11.5.2[g]).
- VAV with Reheat: Minimum volume set points for VAV reheat boxes shall be 30% of zone peak airflow or the minimum ventilation rate, whichever is larger, consistent with Exception 1(a) to Section 126.96.36.199. The supply air temperature for cooling shall be reset higher by 5°F under the minimum cooling load conditions.
- Direct Expansion: The fuel type for the cooling system shall match that of the cooling system in the proposed design.
- VAV: Constant volume can be modeled if the system qualifies for Exception (2) to Section 188.8.131.52. Otherwise, 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 G184.108.40.206. 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 220.127.116.11.3 shall be modeled.
- 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 44°F design supply temperature and 56°F return temperature. Piping losses shall not be modeled in either building model. Chilled-water supply water temperature shall be reset in accordance with Section 18.104.22.168. 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 22 W/gpm (equal to a pump operating against a 75 ft 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 22.214.171.124. 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 10°F:
Approach10°FRange = 25.72 — (0.24 × WB)
where WB is the 0.4% evaporation design wet-bulb temperature in °F, valid for wet bulbs from 55°F to 90°F.The tower shall be controlled to maintain a 70°F leaving water temperature where weather permits, floating up to leaving water temperature at design conditions. 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 19 W/gpm (equal to a pump operating against a 60 ft 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.
- 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 600,000 Btu/h or less and with two equally sized boilers for plant capacities exceeding 600,000 Btu/h. Boilers shall be staged as required by the load. Hot-water supply temperature shall be modeled at 180°F design supply temperature and 130°F return temperature. Piping losses shall not be modeled in either building model. Hot-water supply water temperature shall be reset in accordance with Section 126.96.36.199. 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 19 W/gpm (equal to a pump operating against a 60 ft 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 188.8.131.52.
- Electric Heat Pump and Boiler: Water-source heat pumps shall be connected to a common heat pump water loop controlled to maintain temperatures between 60°F and 90°F. Heat rejection from the loop shall be provided by an closed-circuit axial-fan evaporative fluid cooler with two-speed fans if required in Section 184.108.40.206. 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 600,000 Btu/h or less and with two equally sized boilers for plant capacities exceeding 600,000 Btu/h. 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 22 W/gpm, which is equal to a pump operating against a 75 ft 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 220.127.116.11. Loop pumps shall be modeled as riding the pump curve or with variable-speed drives when required by Section 18.104.22.168.
- 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 40°F.
- 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.
- Fan Speed Control: Fans shall operate as one or two speed as required by Section 22.214.171.124, regardless of the fan speed control used in the proposed design.
Table 11.5.2-2 Number of Chillers
|Total Chiller Plant Capacity||Number of Chillers|
|>300 tons, <600 tons||Two sized equally|
|≥600 tons||Two minimum with chillers added so that no chiller is larger than 800 tons, all sized equally|
Table 11.5.2-3 Water Chiller Types
|Individual Chiller Plant Capacity||Electric Chiller Type||Fossil Fuel Chiller Type|
|≤100 tons||Reciprocating||Single-effect absorption, direct fired|
|>100 tons, <300 tons||Screw||Double-effect absorption, direct fired|
|≥300 tons||Centrifugal||Double-effect absorption, direct fired|
Table 11.5.2-4 Economizer High-Limit Shutoff
|Economizer Type||High-Limit Shutoff|
|Water (integrated)||When its operation will no longer reduce HVAC system energy|
Compliance shall be documented and submitted to the authority having jurisdiction. The information submitted shall include the following:
- The energy cost budget for the budget building design and the design energy cost for the proposed design.
- A list of the energy-related features that are included in the design and on which compliance with the provisions of Section 11 is based. This list shall document all energy features that differ between the models used in the energy cost budget and the design energy cost calculations.
- The input and output reports from the simulation program, including a breakdown of energy usage by at least the following components: lights, internal equipment loads, service water-heating equipment, space-heating equipment, space cooling and heat-rejection equipment, fans, and other HVAC equipment (such as pumps). The output reports shall also show the amount of time any loads are not met by the HVAC system for both the proposed design and budget building design.
- An explanation of any error messages noted in the simulation program output.
- The reduction in design energy cost associated with on-site renewable energy.