The performance approach may be used for whole building permit applications; or for permit applications that involve any combination of building envelope, indoor lighting, and/or mechanical system. The performance method may be used to demonstrate compliance with the envelope alone or the mechanical system alone but cannot be used to show lighting compliance alone. A permit stage is when less than a whole building is being considered (e.g. the building envelope would be constructed in one permit phase, the mechanical system in another, etc.).
Whole buildings are projects involving buildings where the applicant is applying for permits and submitting plans and specifications for all the major components of the building (envelope, mechanical, indoor lighting, and service water heating). This could be a first time tenant improvement that involves envelope, mechanical and lighting compliance, where plans and specifications for the entire building are being submitted for permit.
When a whole building is modeled using the performance approach, trade-offs can be made between the envelope, space conditioning, service water heating, and indoor lighting systems that are included in the permit application.
Compliance with only one or more building permit stages can be done using the performance approach except that indoor lighting cannot be done alone. A permit stage is a portion of a whole building permit: either envelope, mechanical, or lighting. This means that trade-offs in energy use are limited to only those features, or a single feature in the case of envelope or mechanical, included in the building permit application.
There are two basic scenarios that occur when performing compliance by permit stage:
1. Modeling future construction features that are not included in the permit application
2. Modeling existing construction that has complied with the Energy Standards.
11.4.2.1 Modeling Future Construction by Permit Stage
When a feature of a building is not included in the permit application, it is required to default to a feature automatically determined in the compliance software. The defaults vary for envelope, mechanical, and indoor lighting. The Nonresidential ACM Reference Manual and the software vendor’s compliance supplements contain additional information on the default values.
The default envelope features do not apply when modeling future construction. Usually, this is the first permit requested and this feature must be modeled at a minimum. The proposed building's envelope features are input and an energy budget is automatically generated based on the proposed building's envelope, and/or space conditioning and indoor lighting system.
The default space conditioning system features are determined as described in the Nonresidential ACM Reference Manual.
The default lighting system features depend on whether or not the occupancy of the space is known. If the space occupancy is known, the allowed lighting power is determined using the Area Category Method for each zone that the occupancy is known. If the space occupancy is not known, 0.40 W/ft² is assumed for both the proposed energy use and the energy budget
The default service water heating system is determined as described in the Nonresidential ACM Reference Manual.
11.4.2.2 Modeling Existing Construction by Permit Stage
When existing indoor lighting or an existing mechanical system is not included in the permit application, the compliance software may use default values for certain inputs. The Nonresidential ACM contains additional information on the default values.
The envelope features are based on the compliance software user's inputs to the compliance software. The user inputs the proposed building's conditioned floor area, glazing, wall, floor/soffit, roof/ceiling, and display perimeter features. The compliance software then applies the proposed building's features to the standard design in order to calculate the energy budget. If an application for an envelope permit is not being sought, the compliance software will automatically default the features of the standard design to be the same as the features of the proposed design.
Default space conditioning system features depend on the building's existing space conditioning system. The user can either input the existing space conditioning system, including actual sizes and types of equipment, or specify that the existing system is unknown. When the existing system is entered, the compliance software applies the proposed building's space conditioning features to create a similar standard design mechanical system used to calculate the energy budget. This means that if an application is not being sought for a mechanical permit, the compliance software will automatically default the features of the standard design to become the proposed design. When the system is unknown, the software will automatically create a system in the proposed design to match the standard design.
The default service water heating system is determined as described in the Nonresidential ACM Reference Manual and will only be listed as "Existing".
Default lighting system features are based on the known occupancy of the building. The allowed lighting power is determined based on the Area Category lighting power for the proposed design, or an existing modeled lighting power from field data. The compliance software then applies the proposed building's indoor lighting power to the standard design in order to calculate the energy budget. This means that if an application for a lighting permit is not being sought, the compliance software will automatically default the lighting features of the standard design to be the same as the lighting features of the proposed design.
An addition that consists of both new conditioned floor area and added volume will be treated similar to a new building in the performance approach. All systems serving the addition will require compliance to be demonstrated; and either the prescriptive or performance approach can be used for each stage of the construction of the addition.
Note: When existing space conditioning or water heating is extended from the existing building to serve the addition, those systems do not need to comply with new construction energy efficiency requirements; however, all applicable mandatory measures must be met for new components and controls.
11.4.3.1 Addition Only
Additions that show compliance with the performance approach independent of the existing building must meet the requirements for new buildings. §141.0(a) states that the envelope and indoor lighting of the addition, any newly installed space conditioning, electrical power distribution system, or water heating system must meet mandatory measures and the applicable energy budget:
1. If the permit is done in stages, the rules for each permit stage apply to the addition’s performance run.
2. If the whole addition (envelope, lighting and mechanical) is included in the permit application, the rules for whole buildings apply.
11.4.3.2 Existing Plus Addition
Additions may also show compliance by either:
1. Demonstrating that efficiency improvements to the envelope component of the existing building, as well as certain indoor lighting and mechanical improvements, offset substandard addition performance (see §141.0(a)2Bii).
2. Showing that the existing building combined with the addition meet the requirements of §141.0(b) as new construction.
§141.0(a)2 states that the envelope and indoor lighting in the conditioned space of the addition, and any newly installed space conditioning, electrical power distribution system or service water heating system, must meet the mandatory measures. The energy use of the combination of the altered existing building plus the proposed addition shall be equal to or less than the energy use of the existing building with all alterations meeting the requirements of §141.0(b)2 plus the standard energy budget of an addition that complies with §140.1.
This approach allows the applicant to improve the energy efficiency of the existing building so that the entire building meets the energy budget that would apply if the existing building were unchanged, and the addition complied on its own. Changes to features in the existing building are considered alterations.
For a full description of when and how altered components in the existing building are counted as a credit or penalty in the performance calculation, as well as basic energy modeling rules for alterations, see Section 11.4.4.2 below.
Example 11-2
Question
3,000 ft² of conditioned space is being added to an existing office building. 25% of the lighting fixtures in the existing office space are being replaced with more efficient fixtures. Can credit be taken for the improved lights in the existing building to comply through the existing-plus-addition performance approach?
Answer
Credit can only be taken for lighting efficiency improvements resulting in a lower lighting power than is required to meet §140.6. Otherwise, credit may be taken for improvement(s) to the envelope components only. Lighting in the existing building must meet all prescriptive requirements in this case (more than 10 percent of the lighting fixtures are replaced or the connected load is increased).
Using the performance approach for an alteration is similar to demonstrating compliance with an addition.
11.4.4.1 Alterations of the Permitted Space
Altered spaces can show compliance with the performance approach independent of the remainder of the existing building, but must still meet the requirements for the altered components of the building as specified in §141.0(b)2. These require that envelope and lighting alterations, as well as any new or replacement space conditioning or service water heating system serving the alteration, meet the mandatory measures. The permitted space alone may comply with the energy budget determined using approved compliance software.
If the permit is done in stages, the rules for each permit stage apply to the alteration performance run.
11.4.4.2 Alterations in Existing Buildings without an Addition
Alterations may also show compliance by demonstrating that the energy use of the proposed design -- including all energy efficiency improvements to the existing building -- is equal to or less than the standard design energy budget which is based on the alterations meeting the requirements of §141.0(b)2 and Table 141.0-E of the Energy Standards. Note that §141.0(b)2 also requires that envelope, lighting, space conditioning and service water heating system alterations meet the applicable mandatory measures.
This approach allows the applicant to improve the energy efficiency of the existing building so that it meets the energy budget that would apply to the entire building if the existing building other than the portion being altered was unchanged. Changes to features in the existing building are considered alterations.
An energy penalty is assigned to any altered component that does not meet or exceed the requirements of §141.0(b)2. A credit is assigned to an alteration (improvement) that exceeds the requirements in §141(b)2 as summarized in Table 141.0-E of the Energy Standards and further detailed in the Nonresidential ACM Reference Manual. The compliance software sets the standard design for the altered component as listed in Table 141.0-E of the Energy Standards.
This compliance approach includes the entire building which means the ensemble of all enclosed space in a building, including the space for which a permit is sought, plus all conditioned and unconditioned space within the structure. The inclusion of the characteristics of unconditioned spaces have an effect on the overall performance budget of the building due to the loads of the unconditioned spaces adjacent to the conditioned spaces which can be beneficial or detrimental to the overall compliance margin.
When using this compliance approach it is important to take into account all changes in the building's features that are:
•EXISTING (that remain unchanged);
•ALTERED (improved or replacement); and
•NEW (all new).
Note that surfaces which are being completely removed from the existing building – roofs/ceilings, exterior walls and floors, and all glazing removed within those surfaces – are not modeled.
To show compliance with this approach you need to follow the instructions in the compliance software user’s manual. Documentation of the existing building’s glazing areas is required to be submitted with the permit application if this method is used for replacement fenestration credit.
Example 11-3
Question
Alterations to an existing office building in Climate Zone 12 includes replacing all single clear metal frame operable windows with new NFRC-rated windows (U-factor =0.45, SHGC=0.31.) What standard design values will the compliance software use for the replacement fenestration area?
Answer
The standard
design will use the values in Table
141.0-A (U=0.47, SHGC=0.31 and VT=0.32) of the Energy Standards regardless
of whether the replacement windows’ values exceed those Table
141.0-A values of the Energy Standards.
11.4.4.3 Existing-Plus-Addition-Plus-Alteration
For additions, the most flexible compliance method is to consider the entire existing building along with the addition (Existing + Addition + Alteration). The combination of additions and alterations to the existing building may be shown to comply by demonstrating that the proposed design energy use is equal to or less than the standard design energy budget based on the alterations meeting the requirements of §141.0(b)2 summarized in Table 141.0-E of the Energy Standards and additions meeting the requirements of §141.0(a)2.
For a full description of when and how altered components in the existing building are counted as a credit or penalty in the performance calculation, see Section 11.4.4.2.
Using this compliance method, credit may be taken for energy efficiency features added to the existing building. When the prescriptive approach is used, compliance can be demonstrated if the altered component meets or exceeds the requirements of §141.0(b)1 and §141.0(b)2 for that component. When the performance approach is used, the altered component must meet or exceed the requirements in §141.0(b)1. and §141.0(b)3, or other alteration(s) must be made to the existing building that exceed the requirements of §141.0(b)3 and saves the additional energy necessary to make up for the alteration(s). Alternatively, when there is an addition, the addition can be designed to exceed prescriptive requirements to offset proposed existing building alterations that do not meet prescriptive requirements.
Alterations may include previous fenestration improvements that were made to the building after original permit (when the existing building was first constructed). The upgraded efficiency values of the current fenestration must be documented as the proposed design; and the standard design is based on the current Energy Standards. The permit applicant must provide evidence that the previous glazing improvements were made subsequent to the original construction of the building and documentation to confirm the glazing type of the previously existing fenestration. Such evidence may involve a receipt, a signed statement from previous owners, or in case where previous owners are not available, a signed statement of the current owner or other record. Note that previous fenestration improvements that have been used to achieve compliance for previous additions and alterations cannot be considered for compliance for subsequent additions and alterations.
Any addition, alteration or repair may demonstrate compliance by meeting the requirements applicable to new buildings for the entire building. Using this method, the entire building could be shown to comply in permit stages or as a whole building. The rules for new buildings permit stage compliance (Section 11.4.1) and whole building compliance (Section 11.4.2) would apply.
Documentation of the existing building’s features is required to be submitted with the permit application if this method is used.