ASHRAE Standard 90.1 has requirements to address the energy used for heating, cooling, ventilation, interior lighting, hot water, and a few other end uses. The standard defines these components of energy use as regulated. But there is a multitude of unregulated energy use within the building that is not addressed by the standard, including:
- All the things that are plugged into convenience outlets such as personal computers, printers, coffee machines, refrigerators and desk lamps;
- Commercial refrigeration equipment such as walk-in refrigerators, walk-in freezers, and other equipment common to restaurants, food stores, and convenience stores;
- Transportation systems such as elevators, escalators, and moving walkways;
- Special ventilation systems, for instance to remove carbon monoxide from parking garages;
- Grills, ovens, fryers, steam trays, and other cooking equipment in restaurants and cafeterias;
- Compressed air systems in manufacturing and warehouse facilities; and
- Specialized equipment in laboratories, hospitals, and manufacturing plants.
Energy modelers and software developers must be able to distinguish between regulated and unregulated energy use since this is an important factor in determining the PCI target for compliance with 90.1-2016. In this case, the target performance cost index (PCIt) assumes that the unregulated energy use is neutral for both the proposed design and the baseline building, and the procedure for determining PCIt has adjustments for the percent of unregulated energy.
The type of project could be any one or combination of the following:
- New building
- Additions to an existing building
- Alterations of an existing building
Baseline for unmodified existing building systems or components is the same as the baseline for new systems and components except for vertical fenestration area in existing buildings, as described in Section 3.5.8. However, it is acceptable to predict performance using building models that exclude parts of the existing building, provided that all of the following conditions are met:
a. Work to be performed in excluded parts of the building shall meet the requirements of Sections 5 through 10 of Standard 90.1-2019.
b. 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.
c. 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 essentially the same.
d. 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 shall reflect the utility block or rate for the building plus the addition.
The type of project could be any one or combination of the following:
- New building
- Addition to an existing building
- Alteration of an existing building that meets 90.1 2022 G3.1.4a (i.e., Major Alteration which follows Standard 90.1-2022 Section G3.2)
- Alteration of an existing building that does not meet 90.1 2022 G3.1.4a (i.e., Minor Alteration which follows Standard 90.1-2022 Section G3.3)
Standard 90.1-2022 Section G3.1.4a requires alterations that include the replacement of two or more of the following develop models in accordance with Standard 90.1-2022 Section G3.2.
- 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;
- 50% or more of the luminaires in the alteration area;
- 25% or more of the building envelope area of the alteration portion of the building, including new exterior cladding, fenestration, or insulation.
All other alterations (i.e., minor alterations) are required to develop models in accordance with Standard 90.1-2022 Section G3.3.
For projects following G3.2 the baseline for unmodified existing building systems or components is the same as the baseline for new systems and components except for vertical fenestration area in existing buildings, as described in Section 3.5.7.
Section G3.3 was added to 90.1 in 90.1 2022. It specifies that the 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 and as described in Section G3.3.2. All other baseline systems and equipment are required to be modeled the same as in the proposed design.
Figure 1 below is a flowchart for determining the baseline requirement for alterations following 90.1-2022 Section G3.3.
Figure 1: Flowchart for Determining the Baseline Requirement for Alterations Following G3.3
See examples below that illustrate when an alteration would be required to follow G3.2 versus G3.3.
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.
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.
Areas Allowed to be Excluded from the Energy Models
Regardless of whether a project is following G3.2 or G3.3, it is acceptable to predict performance using building models that exclude parts of the existing building, provided that all of the following conditions are met:
a. Work to be performed in excluded parts of the building shall meet the requirements of Sections 5 through 10 of Standard 90.1-2022.
b. 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.
c. 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 essentially the same.
d. 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 shall reflect the utility block or rate for the building plus the addition.