90.1 2022 Section G3.3 Performance Calculations for Other Alterations

90.1 2022 Performance Rating Method

Section G3.3 Performance Calculations for Other Alterations was added to 90.1 in 90.1 2022. It specifies that where an alteration does not meet 90.1 Section G3.1.4a and is therefore required to follow Section G3.3, the baseline building systems and equipment in the scope of the retrofit should be modeled at efficiency levels meeting the mandatory and prescriptive requirements in Section 5 through 10 and as described in Section G3.3.2. All other baseline systems and equipment shall be modeled the same as in the proposed design. For reference Section G3.1.4 language is provided directly below.

G3.1.4 Alterations. The simulation model for calculating the proposed building performance and baseline building performance for alterations, excluding additions, shall be developed in accordance with the applicable subparagraph (a) or (b).

  1. In accordance with Section G3.2 for alterations that include replacement of two or more of the following:
    1. HVAC systems that account for more than 50% of the capacity serving either the heating or cooling loads of the alteration area. This includes HVAC unitary systems, HVAC terminal units, or components of HVAC central heating or cooling equipment. HVAC terminal units, for the purposes of this section, can include VAV boxes, fan-coil units, VRF room units, or water-loop heat pumps;
    2. 50% or more of the luminaires in the alteration area;
    3. 25% or more of the building envelope area of the alteration portion of the building, including new exterior cladding, fenestration, or insulation.
  2. In accordance with Section G3.3 for all other alterations.
Example 1

Question: A project is replacing a chiller that accounts for 75% of the project alteration area cooling capacity and is replacing 80% of the luminaires in the alteration area, would the project be required to following G3.2 or G3.3? Answer: G3.2 because it meets the criteria associated with both G3.1.4a #1 and #2. G3.1.4a #1 applies to the cooling OR heating capacity and because the chiller serves more than 50% of the cooling capacity associated with the alteration area cooling loads the project meets #1. The project is replacing 50% or more of the luminaires in the alteration area so it meets #2.

Answer: G3.2 because it meets the criteria associated with both G3.1.4a #1 and #2.

G3.1.4a #1 applies to the cooling OR heating capacity and because the chiller serves more than 50% of the cooling capacity associated with the alteration area cooling loads the project meets #1.

The project is replacing 50% or more of the luminaires in the alteration area so it meets #2.

Example 2

Question: A project is only replacing a chiller that accounts for 75% of the project alteration area cooling capacity, would the project be required to following G3.2 or G3.3?

Answer: G3.3 because it only meets the criteria associated with G3.1.4a #1. To be required to follow G3.2 the project would need to meet two or more of the scenarios described in G3.1.4a #s 1-3 and it only meets one.

Example 3

Question: A project is replacing a chiller that accounts for 75% of the project alteration area cooling capacity and is replacing 50% of luminaires in 25% of the alteration area covered by the chiller replacement, would the project be required to following G3.2 or G3.3?

Answer: G3.3 because it only meets the criteria associated with G3.1.4a #1. To be required to follow G3.2 the project would need to meet two or more of the scenarios described in G3.1.4a #s 1-3. The reason the project does not meet G3.1.4a #2 is because the luminaire replacement only applies to 25% of the alteration area so it does not meet the criteria of a 50% or more luminaire replacement in the alteration area.

The figure below is a flowchart to assist with determining the baseline requirement for alterations following 90.1-2022 Section G3.3.

The instructions for filling out the Compliance Form when following G3.3 are as follows:

Submit supplementary documentation where modeled values and assumptions cannot be captured using the methods described in the bullets below. Some examples include baseline HVAC system capacities and modeled baseline efficiency values with fan energy extracted.

  • For projects with no new construction building area in the project (i.e., project only includes floor area subject to G3.3). The project only needs to fill out the tabs and tables associated with proposed design inputs. The baseline tabs/tables do not need to be filled out because the 90.1 Section 5 to 10 prescriptive/mandatory requirements generally auto-populate on the tabs and in tables with proposed design inputs. Because Section G3.3 requires that baseline building systems and equipment in the scope of the retrofit be modeled at efficiency levels meeting the mandatory and prescriptive requirements in Section 5 through 10 it means that the proposed tables will show both proposed and baseline model inputs. However, care should be taken by projects when establishing required model inputs because some Section 5 through 10 prescriptive/mandatory requirements are different for new construction versus alterations and auto populated values in the Compliance Form assume new construction. To address this, projects are instructed to provide an explanation of what inputs values were modeled in the notes sections below relevant Compliance Form tables and to make manual overrides of prescriptive/mandatory requirements, where allowed and as needed, to document compliance with the modeling requirements of Section G3.3.
  • For projects with a combination of new construction and alterations following G3.3. Projects are instructed to provide a comment in the relevant notes sections under tables in the Compliance Form indicating which components/systems were modeled in the baseline following Section G3.3 and what inputs values were modeled.
Review Tips

General requirement: all systems and components not included in the scope of the alteration should be modeled identically in the baseline and proposed.

  1. SG10-P, SG11-P, SG-12-P, SG-13-P, SG14-P, SG15-P, SG16-P, SG17-P, SG18-P, SG19-P. The benchmarks for the proposed designs are selected in Table 4 of the Energy Performance Summary tab of the Compliance Form. The default benchmarks are set based on DOE/PNNL prototype models (the prototype models) as described below:
    1. Proposed design documenting minimum code compliance: the prototype model of the appropriate building type and climate zone, compliant with the same edition of 90.1.
    2. Proposed design documenting performance above code: the prototype model of the appropriate building type and climate zone, compliant with 90.1 2019.
    3. For mixed use buildings: the benchmark energy use is calculated as an area-weighted average.

    Note: A note of caution for projects that include alterations subject to 90.1 Section G3.3: Because alterations following 90.1 Section G3.3 are minor alterations, and many systems and components may be modeled with existing conditions in the proposed per the requirements of 90.1 G3.3.1b, the project may significantly exceed benchmark values for end not affected by the scope of the alteration.

  2. SG10-B, SG11-B, SG-12-B, SG-13-B, SG14-B, SG15-B, SG16-B, SG17-B, SG18-B, SG19-B. The benchmarks for the proposed designs are selected in Table 4 of the Energy Performance Summary tab of the Compliance Form. The default benchmarks for projects following the PRM baseline are set based on DOE/PNNL prototype models10 (the prototype models) using the appropriate building type and climate zone, compliant with 90.1 2004. For mixed use buildings, the benchmark energy use is calculated as an area-weighted average.

    Cautionary note for projects involving alterations following 90.1 Section G3.3: When reviewing projects with alterations following 90.1 Section G3.3, which are by definition minor in nature, it’s important to consider that many systems and components will be modeled with existing conditions in the baseline and proposed models due to the requirements of 90.1 G3.3.1b (i.e., systems and equipment excluded from the scope of retrofit shall be modeled as reflecting the existing conditions in the baseline and proposed models). On the other hand, for systems and components included in the scope of the retrofit, 90.1 Section G3.3.2.1 requires that the baseline be modeled at efficiency levels that align with the mandatory and prescriptive requirements in Sections 5 through 10. Consequently, the default benchmark may not be an appropriate comparison for the baseline results since the 90.1 Section G3.3 rules deviant significantly from the logic used to create the prototype models minimally compliant with 90.1 2004.

    Depending on the relative square footage of the alteration building area following Section G3.3 compared to the total square footage, the benchmark source can be modified in Table 4 on the Energy Performance Summary tab to a more appropriate selection. For example, if the entire project is an alteration following Section G3.3 than a more appropriate benchmark for the baseline may be the version of 90.1 that the project is subject to since systems and components included in the scope of the retrofit are modeled at efficiency levels that align with the mandatory and prescriptive requirements in Sections 5 through 10.

  3. BE05-B. Baseline opaque thermal properties will automatically populate in the Compliance Form based on project climate zone and space conditioning category in the “ASHRAE Prescriptive Requirement” column on the Envelope Areas tab in Table 1. Examine the notes field under the table for additional clarifications and explanations as to what was modeled because 90.1 Section 5.1.4 includes exceptions to the requirements to comply with the auto populated prescriptive requirements.
  4. BE15-B. Baseline fenestration U-factor, SHGC and VT will automatically populate in the Compliance Form based on project climate zone and space conditioning category in the “ASHRAE Prescriptive Requirement” column on the Envelope Areas tab in Table 2. Examine the notes field under the table for additional clarifications and explanations as to what was modeled because Section 5.1.4 includes exceptions to the requirements to comply with the auto-populated prescriptive requirements.
  5. LI03-B. Baseline interior lighting is found in the following tables of the Compliance Form:
    • Table 1 on the Lighting Space Types tab shows whether the project used space-by-space or the building area method.
    • Baseline LPDs are shown in Table 1 of the Interior Lighting Counts tab in the 90.1 Prescriptive group of columns. These values are set automatically by the Compliance Form based on user-provided description of the building area types and space types. Manual overrides may be needed if requirements differ due to the alteration meeting 90.1 Section 9.1.1.3.1b. Manual overrides will show in a bold brown color. Examine the last column of the table for clarifying notes.
    • Spot-check the baseline LPDs in spaces where the proposed LPD is substantially lower than the baseline LPD (based on Table 1 of the Interior Lighting Counts tab). LPD difference over 30% should be flagged.
  6. LI04-P. Only the lighting controls in the proposed design that exceed the minimum requirements of 90.1 Section 9.1.1.3.1 may be modeled differently in the proposed design compared to the baseline. The credits will not auto populate correctly in Table 1 on the Interior Lighting Counts tab. Examine the Additional Notes column on the right end of the table for clarifications regarding what was modeled.
  7. LI05-P. Mandatory lighting control requirements for each space are determined automatically and are shown in Table 1 of the Interior Lighting Counts tab of the Compliance Form in the section labeled “90.1 Mandatory Lighting Control Requirements (For Reference)”. Clarifying notes explaining what is required and why may be needed if requirements differ due to the alteration meeting 90.1 Section 9.1.1.3.1b. Examine the last column of the table for clarifying notes.
  8. LI05-B. Baseline lighting control requirements for each space are determined automatically and are shown in Table 1 of the Interior Lighting Counts tab of the Compliance Form in the section labeled “90.1 Mandatory Lighting Control Requirements (For Reference)”. Clarifying notes explaining what was modeled and why may be needed if requirements differ due to the alteration meeting Section 9.1.1.3.1b. Examine the last column of the table for clarifying notes.
  9. LI06-B. Table 2 of the Compliance Calculations tab shows non-coincident peak demand for interior lighting. The value is taken from the simulation reports and reflects the maximum modeled interior lighting load (kW). Peak lighting demand depends on the modeled lighting wattage, the hourly lighting schedule, adjustments to the hourly schedule to reflect reduced runtime due to occupancy sensors (if applicable) and modeled daylighting controls. The modeled interior lighting peak demand may be compared to the interior lighting wattage reported on the Interior Lighting Summary tab Table 1 “90.1 Prescriptive” column for baseline values. For 90.1 2022 alterations following 90.1 Section G3.3 the coincident peak demand is expected to be lower than the total lighting wattage reported in the Compliance Form due to occupancy sensor and daylighting controls. A multiplier of 0.7 may be used to roughly approximate the impact of such controls on coincident demand, as follows:

    MLD prop < 0.7 * TLW prop

    MLD baseline > 0.7 * TLW baseline

    MLD = modeled noncoincident lighting peak demand from simulation reports[kW]

    TLW = total lighting wattage from Table 1 of the Interior Lighting Summary tab [kW]

    As part of this check, it is also helpful to verify that the non-coincident lighting peak demand reported in the Compliance Calculations tab Table 2 matches simulation reports.

  10. LI08-B, LI08-P. For alterations subject to 90.1 2022 Section G3.3, the credits will not auto populate correctly in Table 1 on the Interior Lighting Counts tab since credit can only be modeled when projects exceed the minimum requirements of 90.1 Section 9.1.1.3. Examine the Additional Notes column on the right end of the table for clarifications regarding what was modeled.
  11. LE01-B. The baseline exterior lighting power for each exterior lighting application are determined automatically and are shown in Table 1 of the Exterior Lighting Counts tab of the Compliance Form in the section labeled “90.1 Individual Lighting Power Allowance [Watt]”. Clarifying notes explaining what was modeled and why may be needed if requirements differ due to the alteration meeting 90.1 Section 9.1.1.3.2b. Examine the Notes field under Table 1 for clarifying notes.
  12. LE02-P. The review tips in the main section can be followed, however, clarifying notes explaining what is required and why may be needed if requirements differ from auto populated values due to the alteration meeting 90.1 Section 9.1.1.3.2b. Examine the Notes sections for clarifying notes.
  13. LE03-B. The modeled baseline exterior lighting wattage must reflect the values reported in Table 2 of the Exterior Lighting tab in the “Total Exterior Lighting Power Allowance, per 90.1 Table 9.4.2-2 + Exempt [Watt]” column. Clarifying notes explaining what was modeled and why may be needed if requirements differ due to the alteration meeting 90.1 Section 9.1.1.3.2b. Examine the Notes field under Table 2 for clarifying notes.
  14. PPO05-B. Energy use of the regulated refrigerators and freezers in the baseline design is established automatically in Table 3 of the Plug, Process and Other Loads tab. However, the calculations are based on the characteristic of the corresponding proposed unit reported in Table 3 below, thus the related inputs should be verified. Cross-check information provided in the Compliance Form to design documents for a sample of units focusing on the units that account for largest difference between baseline and proposed design accounting for unit quantity. Reference to appropriate design documents where each unit is described must be provided in the last column of Table 3. If details that must be captured in Table 3 are not available in the design documents, request equipment cutsheets or manufacturer literature. The baseline kWh/day value will be shown in the "ASHRAE 90.1 2022 Prescriptive Requirement kWh/Day/Unit" column since the baseline is required to be modeled as minimally compliant with Section 6. Examine the Notes field under the Table for clarifying notes.

    Table 9 on the Plug, Process and Other Loads tab includes information about walk-in cooler and freezer equipment. Similar to above, cross-check information provided in the Compliance Form to design documents for a sample of units.

  15. PPO06. Since regulated refrigerators and freezers are rated in kWh/day, annual energy use reported in Table 2 of the Compliance Calculations tab, should be equal to the sumproduct of the "ASHRAE 90.1 2022 Prescriptive Requirement kWh/Day/Unit" and the “Qty of Units” columns in Table 3. Discrepancies should be flagged. Examine the Notes field under the Table for clarifying notes.
  16. SWH02-B. Baseline SWHs are required to be modeled with the same system types as specified in the proposed design and as meeting Section 7.1.4. Table 1 on the Service Water Heating tab shows the SWHs specified in the proposed design model and in the “ASHRAE 90.1 Minimum Eff.” and the “ASHRAE 90.1 Maximum Stand-by Loss” columns the minimum efficiency requirements of Section 7.1.4 autopopulate. Default values over-written by the modeler are shown in brown bold font in the table and should be verified by reviewer. Examine the Notes field under the Table for clarifying notes.
  17. AHVAC03-B. Baseline HVAC system types are reported in Table 1a of the Proposed HVAC tab since the baseline HVAC system type is required to be modeled the same as the proposed design with the exception that if the proposed design includes variable refrigerant flow heat pumps or single-zone systems with electric resistance heat, then air source heat pumps shall be used in the baseline design. Spot-check to confirm that the baseline system types were established correctly based on this exception. Examine the Notes field under the Table for clarifying notes.
  18. AHVAC05-B. Assess heating, cooling, fan, and pump savings in Table 1 on the Energy Performance Summary tab. If savings appear greater than expected based upon the specified efficiency of the proposed design systems and equipment (i.e., there are few systems and components that impact HVAC that exceed the minimum requirements in Sections 5-10, yet the project is showing significant savings) then check the supplemental documentation showing the modeled baseline capacities using review tips #2 under Review Tips – ECB and #4 under Review Tips – PRM under AHVAC05-B.
  19. AHVAC08-B. Heating and cooling system efficiencies are reported in Table 1a of the Proposed HVAC tab in the “ASHRAE 90.1 Minimum Allowed Efficiency” column and are auto-populated based on user inputs in upstream columns for heating and cooling. Any over-written defaults which are shown in brown font should be confirmed by the reviewer. Examine the Notes field under the Table for clarifying notes.
  20. AHVAC15-B. Specified fan power is entered on the Proposed HVAC tab in Table 2a with fan system pressure drop adjustments entered in Table 3. If the proposed design includes energy recovery but it is not required in the baseline building design per Sections 6.1.4 and 6.5.6 then the pressure drop adjustment for energy recovery should be removed from Table 3 so that the required baseline fan power populates. The total specified fan power is shown in Table 3 in the “Total Specified Fan System Power” section of columns. Each row with a cell in the “BHP” column that has a green border should be modeled with the corresponding kW/CFMs shown in the “kW/CFMs” column in the baseline. If a red border is shown, then the baseline fan power should be capped at the BHP shown in the “ASHRAE 90.1 Max. Allowed BHP (for reference)” column.
  21. AHVAC16-B. Refer to the Notes sections under Table 4 on the Proposed HVAC tab for baseline modeling inputs for alterations subject to 90.1 2022 Section G3.3 (i.e., Minor alterations).
  22. AHVAC17-B. Refer to the Notes sections under Table 2a on the Proposed HVAC tab for baseline fan curves for alterations subject to 90.1 2022 Section G3.3 (i.e., Minor alterations). Fan curves should be modeled based on the minimum requirements of 90.1 Section 6.1.4.
  23. AHVAC19-B, AHVAC19-P. Refer to Table 3 on the Proposed HVAC tab and the Notes section under the table for modeled baseline fan power and confirm that it is generally consistent with non-coincident peak demand reported in the Compliance Calculations tab Table 2 for both baseline and proposed designs.
  24. AHVAC21-B. Refer to Table 4 on the Proposed HVAC tab for baseline requirements for air-side economizers. Note that unless the scope of the alteration includes the installation of a new cooling system to serve previously uncooled spaces an economizer is likely not required to be modeled in the baseline because 90.1 Section 6.5.1 is not included under 90.1 Section 6.1.4.1. Examine the Notes field under the Table for clarifying notes and the ‘Exceptions to 6.5.1, if Any” column for applicable exceptions.
  25. AHVAC23-B. Refer to the Notes section under Table 2a on the Proposed HVAC tab for clarifying notes regarding the OA CFM rates modeled in the baseline design model. If different rates are modeled in the baseline and proposed design models the reviewer should verify that this was required based on the scope of the alteration and the language and corresponding Sections associated with 90.1 Section 6.1.4.
  26. AHVAC25-B. Demand control ventilation requirements applicable to each baseline HVAC system are shown in Table 4 on the Proposed HVAC tab in the “Min. Floor Area ft^2 in which DCV is Req’d per 6.4.3.8. (Populates only after EAER columns are filled out.)” column. The values are auto-populated in the Compliance Form based on user-specified maximum occupant density. Overwritten defaults should be reviewed to verify that the exception referenced in the Compliance Form is properly applied. Examine the Notes field under the table for clarifying notes. 90.1 Section 6.1.4.1 only requires DCV for single-zone equipment. If the alteration includes the installation of a new cooling system to serve previously uncooled spaces, then it is subject to 90.1 Section 6.1.4.2 and the baseline should be modeled as minimally compliant with all mandatory and prescriptive requirements in 90.1 Section 6 including 90.1 Section 6.4.3.8 for all equipment types.
  27. AHVAC27-B. The systems and equipment included in the scope of retrofit for alterations subject to 90.1 2022 Section G3.3 are likely required to model exhaust air energy recovery identically in the baseline and proposed. This is because 90.1 Section 6.1.4.1 does not include a reference to 90.1 Section 6.5.6 (the section that set requirements for Exhaust Air Energy Recovery). However, if the alteration includes the installation of a new cooling system to serve previously uncooled spaces, then the baseline should be modeled as minimally compliant with all mandatory and prescriptive requirements in 90.1 Section 6 including 90.1 Section 6.5.6. Examine the Notes section under Table 4 on the Proposed HVAC tab for clarifying notes as to what was modeled and why in the baseline.
  28. WHVAC01-B. Minimum efficiency requirements are reported in Table 6a on the Proposed HVAC tab in the “ASHRAE 90.1 Minimum Efficiency Full Load Path A/Path B” and “ASHRAE 90.1 Minimum Efficiency Part Load Path A/Path B” columns and are auto-populated based on user inputs in upstream columns. Any over-written defaults, which are shown in brown font, should be confirmed by the reviewer. The baseline chillers are auto-sized, and the resultant chiller capacity will likely differ from the proposed and may put the systems in a different efficiency bracket in Table 6.8.1-3 compared to the proposed. In this case, the auto populated efficiency values would not be accurate since the proposed capacity is entered in Table 6a. Examine the Notes field under the table for clarifying notes as to what was modeled in the baseline design model and for the capacity of the baseline chillers.
  29. WHVAC04-B. Chilled water loop proposed design parameters are entered in Table 5a on the Proposed HVAC tab. Examine the Notes field under the table for notes regarding what was modeled in the baseline design model. The baseline and proposed design loop configuration and temperature controls should be modeled the same because 90.1 Section 6.1.4.1 does not include any relevant references to sections that pertain to loop design parameters and controls. Exception: if the alteration includes the installation of a new cooling system to serve previously uncooled spaces, then it is subject to 90.1 Section 6.1.4.2 and the baseline should be modeled as minimally compliant with all mandatory and prescriptive requirements in 90.1 Section 6 including all those that relate to chilled water systems and controls.
  30. WHVAC06-B. Chilled water pump proposed design parameters are entered in Table 5a on the Proposed HVAC tab. Examine the Notes field under the table for notes regarding what was modeled in the baseline design model. Section 10.1.4, which is applicable to alterations, includes minimum motor efficiency requirements that should be modeled for the pump motors in the baseline.
  31. WHVAC10-B. Proposed heat rejection systems are entered in Table 6a on the Proposed HVAC tab. The same heat rejection system type should be modeled in the baseline and proposed. Examine the Notes field under the table for notes as to what was modeled in the baseline design model. Baseline system parameters should be modeled as minimally compliant with Table 6.8.1-7 and Section 6.5.5.2 which includes requirements for fan speed control.
  32. WHVAC12-B. Proposed boiler type and quantity are defined in Table 7a on the Proposed HVAC tab. The same boiler quantity and type should be modeled in the baseline design model. Boiler efficiency shall be modeled with the minimum requirements of Table 6.8.1-6 in the baseline. If the auto-sized baseline boiler system falls into the same capacity bracket as the proposed, the baseline efficiency will auto-populate in the “ASHRAE 90.1 Minimum Performance Requirement” column. Examine the Notes field under the table for notes as to what was modeled in the baseline design model.
  33. WHVAC17-B. Proposed hot water pump parameters are defined in Table 5a on the Proposed HVAC tab. Examine the Notes field under the table for notes as to what was modeled in the baseline design model. The baseline and proposed design loop configuration and temperature controls should be modeled the same because 90.1 Section 6.1.4.1 does not include any relevant references to sections that pertain to loop design parameters and controls. Exception: if the alteration includes the installation of a new cooling system to serve previously uncooled spaces, then it is subject to 90.1 Section 6.1.4.2 and the baseline should be modeled as minimally compliant with all mandatory and prescriptive requirements in 90.1 Section 6 including all those that relate to hot water systems and controls. Section 10.1.4, which is applicable to alterations, includes minimum motor efficiency requirements that should be modeled for the pump motors in the baseline included in the scope of the alteration.
  34. WHVAC22. All fuel types reported in the Proposed HVAC tab Table 1a or 7a should have the corresponding modeled energy use reported for the proposed design on the Compliance Calculations tab in Table 2. All fuel types that are not listed in the above-referenced tables of the Proposed HAC tab are expected to have no energy user reported in the Compliance Calculations tab.