Hi,
We've got the review comments from USGBC that says:
"Please provide a separate ventilation rate procedure calculation for each multiple-zone recirculating system serving the LEED-NC project. Note that an upgraded version of the IEQp1 Prerequisite Form (Form v04) is available, which includes a calculator appropriate for documenting multiple-zone recirculating systems; however, it cannot properly calculate ventilation requirements for multiple zone recirculating systems with recirculation at the zone level (e.g. fan powered induction units). Though not required, it is strongly encouraged that the project upgrade to the most recent version of the credit form. Projects may request a form upgrade through the feedback button in LEED Online v3. Please include the specific prerequisite form, project number, project name, and rating system when requesting an upgrade.
Please help on how can we respond since this project provides all single unit controlled by one (1) Thermostat, although they serving several rooms or areas. Also, we used form V04 on this credit. Should we submit the same template and provide narrative documents. What do you mean by multiple-zone recirculating system?
Appreciate quick respond ont this.
Susan
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
October 29, 2012 - 2:45 pm
Hi,
Follow-up question please. If more than (1) occupiable space type ventilation zone (e.g. office/conf. meeting/breakrooms) is present within one thermal zone, is it considered as multi-zone?
Can anyone please differentiate the single zone to multi-zone?
thanks,
susan
Ward Miller
Chief Environmental OfficerAlpenglow Advisory
64 thumbs up
October 30, 2012 - 1:10 am
Hi Susan,
You may want to read below the post by Todor Boyadzhiev from Aug 04 2012 IEQp1- A3 Table Mechanical Ventilation 100%OA. It sounds like you are facing a similar review as the one we recently had. I am not sure why, but GBCI assumed we had a multi-zone recirculation system as well. GBCI actually wrote they could upgrade to V5 of the form, but since it was not posted for our review we opted for V4; I would suggest requesting V5, as we found V4 also had bugs. In terms of submitting, I would first ensure 1) whether you have recirculation in your system (Do you have ventilation intake sourcing air in the building? If not, you have a 100% outdoor air system and should avoid checking any other box in the appendix of the form). In terms of multi-zone, this is a rather arbitrary division the HVAC engineer may have or have not made. In your case it sounds like you may have a single zone system, although you have provided insufficient ventilation detail to be certain as the thermostat is related more to heating and cooling and depending on your sources of these, you may or may not have multiple zone ventilation. If you look through the ASHRAE 62.1 and/or the related User Manual (later found in the Resources section of LEED Online) you will be able to reference the definitions for the terms and provide support to your narrative. Good luck...
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
November 6, 2012 - 7:51 pm
Hi,
thanks for reply. We don't need 100% OSA on this project.
Just another question please.
1. if i only have default system population (66) for AC-2 only, and zero actual Pz how can i calculate the "occupancy diversity (D) %?
Before i used D = Ps (actual population) divided by EPz (sum of total population for the system).
2. It seems V4.0 form is a bug. The calculation of IEQC2 under multi-zone is not x 30% e.g. IEQp1= 660; IEQc2 = 1,004 (660 x30%= 858) same thing. How can we fix this?
3. if i onlly have 2 occupancy category for 1 system e.g. AC-3 : office space & corridors, is this considered as multi-zone and req'd MZ calcs? If not, how can i treat this as single zone.
Any assistance on this is highly appreciated.
thanks,
Susan
Hernando Miranda
OwnerSoltierra LLC
344 thumbs up
November 6, 2012 - 11:03 pm
EQp1 / c2 Form v4.0! You have entered the LEED twilight zone.
Form v4.0 attempts to fix a long time error made by the USGBC hired consultants who wrote the LEED Reference Guide for EQp1/c2. Rather than wait till LEED v4 to fix the error, the USGBC has quietly fixed the error using the Online Forms. The Reference Guide has not been fixed.
Well, at least the USGBC tried to quietly fix the error, but Form v4 does not calculate EQp1 correctly. Use the ASHRAE excel tool and Form v4 and enter the same data into them for a simple system. Use the system in the LEED NC 2009 Reference Guide (RG), Table 1, into both calculation tools. Form v4 calculates an incorrect result. You will also notice that the example in the RG is incorrect.
The example in the Reference Guide (RG) implies you multiply the EQp1 system level OA by 30% to determine if you comply. That is incorrect. The 30% is supposed to applied at the zone level.
If you have different values for Evz (you can use Zp for comparison in Form v4.0) then you will provided a greater percentage OA compared to EQp1 to meet the 30% requirement, than you would if the the EVz values for all zones were the same.
A perfectly distributed system should only require 30% more OA for EQc2 than EQp1.
A system that is not well distributed will require 40% or more OA overall.
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
November 7, 2012 - 11:46 am
thanks for respond but it makes me more confused.
Hernando Miranda
OwnerSoltierra LLC
344 thumbs up
November 7, 2012 - 12:34 pm
The LEED Reference Guide implies a 30% increase at the SYSTEM level meets the requirements for EQc2, BUT the latest version of the LEED Form (v4) requires a 30% increase at the ZONE level. In other words, the Reference Guide example is wrong. An addenda has not been provided by the USGBC to correct the error.
An HVAC system includes all the zones ventilated by it. The zone with the lowest Zone Ventilation Efficiency (Evz) determines how much OA is required at the System level.
The greater the difference between the values of Evz in the system the greater the amount of OA required for EQp1.
The greater the difference between the values of Evz in the system the greater the amount of OA required for EQc1 to meet the 30% requirement at the Zone level.
A system with equal Evz values for all zones will require only 30% more OA at the System level.
A system with UNequal Evz values for all zones will require MORE than 30% more OA at the System level. This is because the zone with the lowest Evz is the boat-anchor for the system. That zone forces the system to provide more OA overall because it is not well designed in terms of ventilation air volume.
ABOUT LEED FORM 4
If you try to compare the percent OA increase between EQp1 and EQc2 using the Form v4 you will get an incorrect answer. The tool calculates EQc2 correctly but not EQp1.
To get the correct answer you have to do this:
1) Use the ASHRAE tool to calculate EQp1
2) Use the Form v4 and ONLY use the results for EQc2
3) Determine the percentage increase
HOW TO FIX OA GREATER THAN 30% REQUIRED FOR EQc2
1) Adjust the amount of ventilation air provided to the zones.
2) Adjust the amounts until you get Zp values that are not much different from each other.
NOTE: I do not like using Zp but LEED Form v4 uses it. The Form should show values Evz because the minimum value is what is used to calculate the required OA at the system level in Form v4. Because Form v4 DOES NOT show Evz you cannot see the calculation error the Form has. The only way to see the error is by comparing an HVAC system using both FORM v4 and the ASHRAE 62.1 Excel tool.