Many space types will not function as regularly-occupied private/individual or multi-occupant spaces, nor will those spaces be utilized for extended periods of time (such as kitchen/break room, meeting room, or conference room). Some unique and smaller (less than 200 SF) programmed space types are infrequently occupied (less than 1 hour) and by only one or a few people at a time. One exception to the credit requirement that "private offices" must have active controls is granted in LEED Interpretation #1645 and clarified in the IDC Reference Guide 2009 Edition, which states that "small private spaces intended for single, temporary occupancy (e.g. for making confidential telephone calls) may be included as part of a larger thermal zone, since changes in occupancy will not cause large swings in the heating and cooling loads." Given the credit intent to reduce energy in occupied spaces and the ruling of LEED Interpretation #1645, we propose to expand the definition for small, temporarily-occupied spaces in two ways: 1. For laboratory buildings/spaces, where loads are typically based on equipment loads, we propose a more specific addition to the definition of Special Occupancy to include spaces that are less than or equal to 200 SF and occupied by two or fewer people for short periods of time. 2. For all project types, we propose an expanded definition of Special Occupancy to include spaces with equal or less than 300 cfm, per ASHRAE 90.1-2007 definition of small zones. ASHRAE 90.1-2007 defines small zones as those with less than 300 cfm, as referenced in Sections 6.3.2.n Criteria, 188.8.131.52.3 Shutoff Damper Controls, and 184.108.40.206.a.4 Simultaneous Heating and Cooling Limitation - Zone Controls. In both of these cases, we propose the space types described above be considered Special Occupancy spaces that may be included as part of a larger thermal zone. Are these definitions acceptable?
No, these spaces cannot be considered Special Occupancy. The credit requirements state that private offices and specialty use spaces must have their own active controls capable of sensing space use and modulating the HVAC system in response to changes in space demand.
Specialty use spaces are considered to be conference rooms, break rooms, classrooms, gymnasiums with variable use patterns, cafeterias, hotel guest rooms, residential dwelling units, and other occupied spaces where energy savings can be achieved by adjusting the temperature setpoints and/or air volume supplied to the space when the space is unoccupied, or densely occupied space where energy savings can be achieved by adjusting the ventilation air supplied to the space when the space is partially occupied. Laboratory spaces would be considered to be specialty use spaces, since these spaces generally have 100% outside air, where setting back the temperatures and/or the fume hood ventilation when the space is unoccupied or the fume hood(s) are not actively in use would lead to significant energy savings. Laboratory prep and laboratory support spaces, and resource rooms would also be expected to achieve energy savings by adjusting the temperature setpoints and/or air volume supplied to the space when the space is unoccupied, since these spaces are frequently unoccupied throughout each day; therefore, these rooms would be considered to be specialty use spaces.
Exception: Spaces that would otherwise be considered specialty use spaces but are smaller than 75 square feet, such as the phone rooms referenced in LEED Interpretation #1645, or a lactation room smaller than 75 square feet are not required to have individual active controls capable of sensing space use and modulating in response to changes in space demand.
Spaces not considered to be specialty use spaces: Open offices, reception areas, warehouse or storage spaces, merchandising spaces, lobbies, nursing stations, manufacturing spaces, auto service bays, library stacks, library multi-occupant reading areas, bank teller areas, hallways, and similar spaces are not considered to be specialty use spaces since these spaces would be expected to be at least partially occupied for the majority of the time the HVAC system is operational, and would not be expected to achieve energy savings by adjusting the temperature setpoints and/or air volume supplied to the space when the space is unoccupied.
Controls capable of sensing space use and modulating the HVAC system in response to changes in space demand include the following:
Interior private offices or interior non-densely occupied specialty use spaces - a separate thermal control for each space. This would be considered sufficient because the space demand is related to internal loads (lighting, occupants, and plug loads). When the occupant leaves the space, particularly if the space has lighting occupant sensors and Energy Star computing equipment, the thermostat will be able to sense a change in space demand, and modulate the HVAC system in response to the change in space demand.
Perimeter offices or perimeter non-densely occupied specialty use spaces - a separate thermal control for each space paired with an occupant-sensing or CO2 sensing device, which is used to set back the temperature setpoint and airflow to the space when the space is unoccupied. In many cases, the occupant sensors used for lighting can be integrated with the HVAC controls. This is necessary in perimeter spaces because the space has both envelope loads and internal loads, and the HVAC system would respond minimally to changes in space occupancy if additional occupant-based setback controls were not in place. For a VRF system, fan coils, or packaged single-zone system, the fan coil serving the room must have the fans set to cycle on and off with loads or to operate on the lowest multi-speed setting for multi-speed fans when the space is detected as unoccupied.
VAV systems with supply air diffusers and room thermostats: Per LEED Interpretation #5273, VAV systems having supply air diffusers equipped with room thermostats for each private office or non-densely occupied specialty use space may be used in lieu of a separate thermal zone per private office or non-densely occupied specialty use space. If this compliance path is followed, the following additional requirements apply:
1. The system must be capable of modulating AHU and zone minimum supply volume down below 0.30 cfm/sf of supply volume for standard VAV terminals, or below 22.5% of the peak design flow rate for fan-powered VAV boxes. For spaces where the minimum outdoor air exceeds the minimum supply volumes specified here, some form of occupant sensing or demand controlled ventilation must be employed to allow these minimum supply volumes to be met.
2. The building control system must include controls for fan static pressure reset.
3. The mandatory requirements of ASHRAE Standards 90.1-2007 and 62.1-2007 must be met.
Densely Occupied specialty use spaces (such as a conference room) - a separate thermal control for each space paired with a CO2 or occupant sensing device, which is used for demand control ventilation and to set back the temperature setpoint to the space when the space is unoccupied.
Related Addenda (Corrections & Interpretations)