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What if after our Preliminary Review we have to re-work the ventilation rate procedure calculations and find that we need to make corrections to the system in order to meet the prerequisite? Can we redo the outside air testing after making corrections? Wo

What if our systems do not meet the required outside air when systems are tested at worst-case conditions?

Our building has a single fan that supplies outside air to multiple AHU’s. Do we need to perform outside air testing at the supply fan or at all AHUs?

We have a VAV system where single AHUs serve multiple zones. Do we need to take outside air measurements at each VAV box?

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EBOM-2009 IEQp1:Minimum IAQ Performance

single or multi-zone?

Our building is fully occupied by the same company, so all the floors have similar open space layout, except for enclosed managers or small meeting rooms. There´s an outside air intake in each AHU level. Each floor is served by one AHU, that provides a mixture of outside air with return air, on a constant volume. There are no VAV´s, no dampers and no different zones in our ventilation plenum. Since the floors are mostly open space, have no critical zones (bigger meeting rooms, in the last floor, are served by different AHUs), and are all of the same type (office space), is it wrong to consider it a single-zone system, and measure the intakes only in the AHU level? Or should I consider it a multizone and go through all the VRP calculations?

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Profile picture for user Dave.Hubka_2
Dave Hubka
Practice Leader - Sustainability
EUA
LEEDuser Expert
510 thumbs up

Fri, 03/15/2013 - 01:36

Outside air measurements are required at the system level. In your case it would be at each AHU. The LEED online template calculator (the appendix section of the template form) is for a constant volume unit that serve a single room. The 62MZ calculator is for all other types. You'll most likely be required to complete a 62MZ calculator and verify the OA at each AHU. Hope this helps Dave

Fri, 03/15/2013 - 17:07

Thank you, Dave, but maybe I was unclear. The question is more about multi zone and single zone systems definition. When LEED refers to multi or single zone UNITS, they mean the same definition of ASHRAE ventilation ZONES? I´m sure my system is a single zone, it´s not common to have multiple zone systems in Brazil. Although in each floor we have different rooms and offices, served by the same AHU, i think my approach in the template should be more for Appendix 1 "Mechanical Ventilation Single Zone Unit", is it right? Thank you!
Profile picture for user Dave.Hubka_2
Dave Hubka
Practice Leader - Sustainability
EUA
LEEDuser Expert
510 thumbs up

Fri, 03/15/2013 - 17:37

Hello Guilherme. Multiple Zone Unit describes an AHU that serves more than one room. Single Zone Unit describes an AHU that serves one room. Systems with local recirculation and/or multiple recirculation paths (such as systems with fan-powered terminal units) should use the 62MZ calculator. If you have a constant volume AHU that serves more than one room, and no terminal units within the system, you can use the Multiple Zone Unit calculator on the LEED online template. (from your description, i believe this to be the path you should choose) If you have a constant volume AHU that serves only one room you will be required to use the Single Zone Unit calculator on the LEED online template. If you have a system with local recirculation and/or multiple recirculation paths you will be required to use the 62MZ calculator. For example, an AHU that serves (1) office and (1) conference room, this is defined as a Multiple Zone Unit (regardless if the system includes local recirc/terminal units). If an AHU serves only (1) office, and no other room, than this is considered a Single Zone Unit. Hope this better clarifies.

Tue, 10/24/2023 - 14:43

Hi Guilherme and Dave, I am following this posts, and they are very usefull regardint ventilation system interpretation. I have the following schenario:
  1. A DOA, that provides outdoor air to VRF evaporators.
  2. Most of the evaporators in the project provides air conditioning to only one zone. These woulf be Single Zone and we should use the LEED calculator.
  3. - Some of them provide air conditiong to two or more zones. If I understood ok, we are dealing with a Multiple zone with recirculation. I we use the LEED calculator my questions are:
  • Which would be the Er? 
  • In this system the Zone Discharge Airflow is the same as the Zone Primary Airflow, is this assumption right?
Thank you!
Profile picture for user Dave.Hubka_2
Dave Hubka
Practice Leader - Sustainability
EUA
LEEDuser Expert
510 thumbs up

Tue, 10/24/2023 - 14:55

In the scenario you describe: Er = 1 zone discharge airflow = zone primary airflow.

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