Please provide additional clarification on "HVAC zone" for this credit. We have a 4 story building. Our current BAS has temperature sensors located on the 1st and 4th floors to provide adequate input to the BAS for Air handler control of supply air temperatures to each of the terminal units in the occupied spaces. We feel that this would meet the intent of the credit, provided we add Humidity sensors in designated "humidity zones". Please comment.
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John Beeson
Green Mystic in Residence107 thumbs up
September 16, 2010 - 10:51 am
As stated, there must be at least one air temperature sensor located in each HVAC zone. As the intent is to provide a comfortable thermal environment, each occupied space should have some degree of monitoring. As stated in the LRG, pg. 405, "...if space uses and configurations make it likely that a single measurement point is not representative..." additional sensor would be required.
A 4 story building with only two temperature sensors, in my mind, would not meet the requirements. It would be unlikely that thermal comfort would be met in all occupied areas by all occupants.
David Grosdeck
Property ManagerCassidy Turley
43 thumbs up
September 17, 2010 - 11:04 am
I am still trying to figure this one out and really need clarification. The bigger picture is that I have a four story 486,000 square foot building split up into 6 "Cores". Each core has it's own air handler that is controlled by the BAS. Each core has temperature sensors on the 1st and 4th floor that send signals to the BAS to control supply air temperatures. Conditioned air is controlled, monitored, and provided to terminal boxes throughout the core. Each terminal box is controlled by a pneumatic thermostat for occupant comfort. Since we have pneumatic thermostats they do not report to the BAS but still provide the occupants a way to control space temperatures.
The recommendation above in the Before the Performance Period section says - "Make sure that there is at least one air temperature sensor located in each HVAC zone." Please define HVAC ZONE in this case.
In the larger picture, we contol and track supply air temperatures throughout each core of the building with our BAS. If you can extend the definition of a "Zone" in this case to correspond to our "Core" we feel comfortable that we meet the intent to provide, monitor, and track conditioned air in occupant spaces.
If "Zone" is defined as an area controlled by an individual thermostat then this credit becomes much more unreasonable and unobtainable. We have over 600 thermostats in the building! I feel it would be very wasteful to remove/replace/retrofit all the terminal boxes and thermostats to expensive DDC controls required to have each thermostat report to the BAS.
We have an excellent Energy Star score and our building engineers are constantly monitoring the BAS to make sure our occupants are comfortable. This is my first experience with a LEED EB project and really need help understanding and meeting the intent of this credit.
Paul C
164 thumbs up
September 17, 2010 - 11:22 am
We have a 5 story multi-tenant office building and discussed with our engineer about defining HVAC zones. We believe the definition of a kitchen requires an exhaust fan so we have ruled all tenant kitchen/break rooms as still office space since they only include sinks, coffee machines...
We therefore will survey conditions throughout each floor and provide evidence as to why we are only using 5 (1 per floor) humidity sensors - assuming that our readings provide the evidence that humidity acorss the floor are same/consistent and there is no need to add additional sensors beyond one per floor.
John Beeson
Green Mystic in Residence107 thumbs up
September 22, 2010 - 8:53 am
David,
If each "core" is served by its own AHU, and the conditioned air from each core is controlled, monitored, and provided to terminal boxes throughout the core, then it would appear to be on the right path.
If understand this correctly, you have six cores running (vertically) through the bldg with air supplied by AHUs. The cores are tapped into by supply ducts at each floor level that serve termination boxes at various locations around the floors?
But please clarify for me: If it is the case that each core has temperature sensors on the 1st and 4th floor that send signals to the BAS to control supply air temperature, what happens on the 2nd and 3rd floors?
David Grosdeck
Property ManagerCassidy Turley
43 thumbs up
September 22, 2010 - 10:31 am
Thank you John. You do understand correctly on the supply ducts. They serve termination boxes at the various locations.
On the floor sensors, the BAS averages the temperatures for the 2nd and 3rd floor to adjust air temperatures. Is this acceptable?
John Beeson
Green Mystic in Residence107 thumbs up
September 22, 2010 - 11:25 am
David,
In my mind, the goal is to provide a comfortable thermal environment in all of the occupied spaces and to do this, the credit requires continuous monitoring of, at a minimum, air temperature and humidity in occupied spaces - that is, at least one air temperature sensor must be located in each HVAC zone. That being said, even though the "cores" might be within range, how does the BAS/managers know if the appropriate temps and humidity levels are being met in the actual occupied areas?
But, now, you got me thinking more. And I could be overthinking it. Do the termination boxes at the end of the supply ducts change the air temperature (warmer/cooler) and, consequently, the humidity?
David Grosdeck
Property ManagerCassidy Turley
43 thumbs up
September 22, 2010 - 11:40 am
I could add temperature sensors to each floor to provide continuous monitoring of temperatures. Humidity sensors would be added to defined humidity zones (kitchens, locker rooms, etc.)
The terminal boxes supply heated or cooled air at a temperature determined by the BAS to the occupied space until the individual thermostats are satisified.
This would be much easier to accomplish with a DDC system. However, the challenge of an Existing building is to provide comfort with the equipment we have. A DDC system with individual thermostat control/monitoring is just not economical to install in this large a facility. If a DDC system is the only way to achieve this credit it is just not possible and puts Existing Buildings at a disadvantage.
I think we are very close to achieving the intent of the credit. I appreciate your help in getting us farther along to obtain our goal. Let me know if you have additional comments or questions.
Thanks!