For controls in perimeter offices or perimeter nondensely occupied specialty use spaces, it says ‘a separate thermal control for each space paired with an occupant-sensing or CO2-sensing device is necessary. Perimeter spaces have both envelope loads and internal loads, and the HVAC system would respond minimally to changes in space occupancy without additional controls.’
We have a project and the base building VAV cannot be linked up with motion sensor nor CO2 sensor, we think of another way in doing this is the ‘booster fan’ concept. This concept is not touching the VAV system but adding another fan linked up with CO2 sensor. If CO2 ppm higher than preset value, indoor air will be extracted from room to open office. More air will be drawn inside the room hence less CO2 level in room.
Is it the appropriate way we can do for perimeter offices or perimeter nondensely occupied specialty use spaces? And does this method meet the credit requirement?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
July 17, 2018 - 11:02 am
For the tenant fit-out of spaces, provide a separate control zone for each solar exposure and interior space. Provide controls capable of sensing space conditions and modulating the HVAC system in response to space demand for all private offices and other enclosed spaces (e.g., conference rooms, classrooms).
For this credit (credit language above) it does not appear that a CO2 sensor is required? Where does the language you provided come from? If it comes from another credit please post you question under that forum.
Amy L
July 17, 2018 - 10:35 pm
Hi Marcus, the statement comes from 'Further Explanation', 'Tenant HVAC Zoning and Controls', ‘Perimeter offices or perimeter nondensely occupied specialty use space’. CO2 sensor or OS is required according to my understanding. Our 'booster fan' concept mentioned above is not some kind of ‘HVAC system would respond minimally to changes in space occupancy without the additional controls’ but a similar approach to do DCV control. So not sure about this concept can meet the credit intent.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
July 24, 2018 - 2:59 pm
Thanks for pointing that out.
I agree that what you propose does not really meet the credit intent of increasing energy performance. It sounds like you would be potentially improving IAQ but you would be adding to energy use with a separate fan.
Chanyang Shin
2 thumbs up
August 7, 2018 - 10:54 am
Marcus,
I also stumbled upon the Further Explanation section for a VAV system that Amy is referencing.
To obtain this credit we are considering tying in all VAV's into the occupancy sensors so that when the room is unoccupied, the airflow (CFM) setpoint would decrease lower than the required ventilation calculated as part of the IAQ Ventilation. A lowered demand for air would have a direct effect on the AHU that serves it since the AHU's fan would be controlled based off static pressure. Hence the fan speed would lower based on rooms being unoccupied.
Given this possibility for energy savings, would this kind of arrangement obtain the HVAC zoning and control credit despite not having 1 VAV per space?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
August 8, 2018 - 12:16 pm
As I read it you would need to have a VAV box connected to a thermostat for each private office or nondensely occupied specialty use space.