The performance approach may be used for whole building permit applications; or for permit applications that involve combinations of building envelope, indoor lighting, domestic hot water (DHW)/service hot water (SHW), and/or mechanical systems. The performance method may be used to demonstrate compliance with the envelope or mechanical system alone but can’t be used to show lighting or DHW 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).
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 DHW/SHW). This also 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, DHW/SHW, 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. DHW and SHW are not considered a permit stage, but these systems may be optionally included (or not included) in the scope of a performance compliance permit.
When building features are outside the scope of the performance compliance permit, those components will automatically be modeled the same in both the standard design and proposed design by the compliance software. By doing this, the software makes these features compliance neutral; meaning no credit or penalty is given for those features. The NRMFACM Reference Manual and the compliance software user’s manual describe these rules and standard design values in detail.
There are two basic scenarios where a building feature will be outside the scope of a performance compliance permit:
1. Modeling future construction features that are not included in the permit application (e.g., future mechanical and lighting systems that are not part of the scope for an envelope only permit).
2. Modeling existing construction that has already complied with the Energy Code (e.g., envelope components, that were permitted in an earlier stage of construction, but are not part of the scope for a mechanical and lighting only compliance run).
When a building feature is not included in the performance calculation and permit, that feature will be defaulted automatically by the compliance software. The defaulting rules vary for envelope, mechanical, and indoor lighting. The NRMFACM Reference Manual and software user’s manual contain additional information on these defaulting rules.
Envelope features can’t be defaulted for permitting at a future stage. Usually, the envelope is the first permit for a building and a fully defined envelope is a requirement for calculating the building’s energy budget.
If mechanical is excluded from the scope of the performance permit, in the case of envelope and/or lighting compliance, the default space conditioning system features are determined as described in the NRMFACM Reference Manual for the mechanical system. In general, the compliance software will create a default, minimum efficiency HVAC system, to neutralize mechanical system compliance.
If lighting is excluded from the scope of the performance permit, the default lighting system features depend on whether 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 and standard design buildings.
If DHW and/or SHW are excluded from the scope of the performance permit, the default DHW/SHW system is determined as described in the NRMFACM Reference Manual. In general, a default, minimum efficient DHW and/or SHW system will be automatically created and used in the proposed building model.
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 NRMFACM Reference Manual contains additional information on the default values.
For existing envelopes, there are no automatic defaults. The user must enter details for the existing envelope, i.e., conditioned floor area, glazing, walls, floors/soffits, roofs/ceilings, and display perimeters. Based on the proposed envelope, the software will create a matching standard design envelope. By doing this all existing envelope features are compliance neutral, no credit or penalty.
To model an existing mechanical system, a user can either input the existing space conditioning system; including the type of equipment, actual sizes, and efficiencies; or specify that the existing system is unknown. When the existing system is entered, the compliance software uses the proposed building's space conditioning features to create a matching standard design mechanical system. This means that all existing mechanical systems in the proposed model are compliance neutral, no credit or penalty. When the system is unknown, the software will automatically create a minimally efficient HVAC system in the proposed design.
The default service water heating system is determined as described in the NRMFACM Reference Manual and will only be listed as "Existing".
Existing lighting system features are based on the known occupancy of the building and whether information on the existing system is known. The lighting power entered for the proposed model is determined based on either the Area Category lighting power allowances for the proposed design occupancies, or if the existing design lighting power is known the actual design data should be entered instead. The compliance software then creates a standard design matching the proposed design so that compliance is neutral, no credit or penalty, for the existing lighting system.
An addition that consists of both new conditioned floor area and added volume will either need to comply as an addition alone or as an existing plus addition plus alteration. For the addition alone path, the same requirements for a newly constructed building will apply to the addition. 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. Existing plus addition plus alteration requires modeling of the existing, altered, and new components, but gives the opportunity for compliance tradeoffs between the new and altered components in the addition and existing building.
When existing space conditioning or water heating is extended from the existing building to serve the addition, the existing components of these systems should be modeled as existing and the new components of these systems must be modeled as new (e.g., new ducts extended to the addition) so that the software can determine the correct standard design based on section 141.0(a) (Nonresidential) or 180.1 (multifamily).
Additions that show compliance with the performance approach independent of the existing building must meet the requirements for newly constructed buildings. §141.0(a) (Nonresidential) and §180.1 (Multifamily) state that the envelope and indoor lighting of the addition, and any newly installed space conditioning, electrical power distribution system, or water heating system must meet mandatory measures and the applicable energy budget:
•If the permit is done in stages, the rules for each permit stage apply to the addition’s performance run.
•If the whole addition (envelope, lighting and mechanical) is included in the permit application, the rules for whole buildings apply.
Additions may also show compliance by either:
7. Demonstrating that efficiency improvements to the envelope component of the existing building, as well as certain indoor lighting and mechanical improvements, offset addition performance that would otherwise not meet the energy budgets for the addition alone (see §141.0(a)2Bii|tag=2__Performance_approach_ (Nonresidential) or 180.1(b)2(Multifamily)).
8. Showing that the existing building combined with the addition meet the requirements of §141.0(b) (Nonresidential) or §180.2 (Multifamily) for newly constructed buildings.
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)3 (Nonresidential) and §180.2(c) (Multifamily) and additions meeting the requirements of §141.0(a)2Bii|tag=2__Performance_approach_ (Nonresidential) or 180.1(b) (Multifamily). Additionally, §141.0(a)2Bii|tag=2__Performance_approach_ (Nonresidential) and §180.1(b) (Multifamily) state 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.
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 the Alterations Performance Compliance section 12.5.4 below.
Example 12--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
Since 10% or
more of the lighting fixtures are replaced, all prescriptive lighting alteration
requirements must be met. Credit can only be taken for lighting efficiency
improvements resulting in a lower lighting power than is required to meet §140.6
(Nonresidential) and §170.2(e)
(Multifamily).
Using the performance approach for an alteration is similar to demonstrating compliance for an addition.
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 (Nonresidential) and §180.2(a) (Multifamily). 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.
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 (Nonresidential) and §180.2(a) (Multifamily) and Table 141.0-E (Nonresidential) of the Energy Code. Note that §141.0(b)1 (Nonresidential) and §180.2(a)(Multifamily) also require 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 (Nonresidential) or §180.2(a) (Multifamily). A credit is assigned to an alteration (improvement) that exceeds the requirements in §141(b)2 (Nonresidential) or §180.2(a) (Multifamily) as summarized in Table 141.0-E (Nonresidential) of the Energy Code and further detailed in the NRMFACM Reference Manual. For Nonresidential, the compliance software sets the standard design for the altered component as listed in Table 141.0-E of the Energy Code and for multifamily the software sets the standard design based on the requirements of §180.2(a).
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 features of the building that are:
•EXISTING (that remain unchanged).
•ALTERED (improved or replaced).
•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 with those removed 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 12-3
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.
See Existing Plus Addition Plus Alteration section in this chapter.
Any addition, alteration or repair may demonstrate compliance by meeting the requirements applicable to newly constructed 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 12.5) and whole building compliance (Section 12.5.1) would apply.
Documentation of the existing building’s features is required to be submitted with the permit application if this method is used.