Hi,
We have existing Library project with combined multiple zone and single zone. We used the V4.0 form as per requirement during initial review, however, our IEQp1 has been denied with comments below from reviewer:
"While population of area served by the sytem for RTU-1 (84) appears to account for the peak transient library patrons and the FTE staff, the occupancy diversity (D) is only 10% resulting in a system population with diversity of only eight. The combined system population for the other AHU is 35. The total sum of the population served by all air handling units after accounting for diversity (D) is only 43, which varies by more than 10% from the peak population density (100) reported for other credits."
Can someone please help us to understand what the reviewer wants. When do we account the system population - from combined system/ all AHU OR to multiple zone only? Likewise, when do we apply occupant diversity - for both or to singel zone.
also, do we need to report both peak cooling mode and heating mode at the same time wherein they have the same values? When we do this, the form did not comply us. When we report heating mode only, still did not comply. Initially, we only show cooling mode but the reviewer looking for calculations for worst case conditions during heating mode.
Appreciate any input/assistance on this.
thanks,
susan
Andrew Mitchell, P.E.
PrincipalMitchell Gulledge Engineering, Inc.
LEEDuser Expert
126 thumbs up
April 27, 2012 - 2:49 pm
Susan, it sounds like other credits are showing an occupancy in the building of up to 100 people and that the OA flow does not account for that many occupants. If the building is designed to hold 100 people then the total of your AHU OA flow calculations should represent a population of 100 people.
As for which mode you need to report, you should report the mode which results in the highest need for OA flow. See ASHRAE 62.1 Section 6.2.5 for Multi-Zone systems. Note that is says your Vpz should be the minimum expected airflow. I always choose to calculate all zones at max design flow then reduce the critical zone to minimum design flow. This will normally give you your worst case scenario. Then I go back and also decrease zones that are similar in thermal type to the critical zone (i.e. if your critical zone is an interior room and is at minimum then most other interior rooms will be at minimum flow). Using that method will definitely require a higher OA flow than if you only calculate it during maximum flow. It is the correct way to calculate it according to ASHRAE 62.1 though.
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
April 27, 2012 - 5:47 pm
Andrew, Thanks for respond.
Yes, we have a total 112 people but it was distributed per AHUs e.g AHU-1 (multi-zone) = 73 + default 5.1; AHU-2 = 17 and AHU-3 = 17.
Likewise, the OA calculation was also reported per each system - multi and single. We have limited field to put our values, you can only adjsut occupant diversity (D) and design OA (cfm), and these values are intended to multi-zone only. It is not part of single zone table. Thus, Im wondering why the reviewer try to connect them which obviously wil affect to our (D) factor. Should i added the cfm for all of these AHUs and report under multi-zone table in order to get (D)? Is there a one time equation that we can follow ? ASHRAE 62.1 seems confusing for too many equations.
thanks again.
Susan
Andrew Mitchell, P.E.
PrincipalMitchell Gulledge Engineering, Inc.
LEEDuser Expert
126 thumbs up
April 30, 2012 - 9:47 am
Susan, I think your best option is to use the ASHRAE 62MZ spreadsheet that can be found on the credit resources link on the credit information page. You can use that spreadsheet for each AHU and show compliance for each space. Upload the spreadsheet and use the alternate compliance. The spreadsheet makes achieving this credit much more user friendly. I hope that helps.
Dylan Connelly
Mechanical EngineerIntegral Group
LEEDuser Expert
472 thumbs up
April 30, 2012 - 11:43 am
Susan,
You received a comment from the LEED reviewer because your System Population with Diversity was more than 10% below the FTE stated by the project in the PI form. This is a red flag for reviewers.
The new v4 Forms allow you to enter in the (D) diversity percentage. This allows you to reduce your system population down to your FTE number. This is beneficial, for example, when you have a system serving conference rooms and offices because people are migrating from the office areas to the conference rooms. Say you have 100 people in an office and all 100 people move into a conference room next door. You need to account for 100 people in each zone, but only 100 total for the system not 200, your diversity factor (D) is 50%.
It looks like you entered in a 10% (D) diversity factor for the first system which took your "System Population without diversity" (Ps) from 84 down to 8.4 people. That is not accurate. If you wanted to account for 73 people in the space served by that system you should have entered in 88% for (D) - 73/84 * 100 = 88.
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
April 30, 2012 - 4:45 pm
Dylan,
I guess you're right. I tried to use 73, the actual Pz/ 78 (total w/ default);
(D) = 73/78 * 100 = 94. Then, system population with diversity = 73. By the way, my FTE = 11 (with peak transients = 89). Are you saying that the totay system population with diversity & without diversity should be equal or to over-all Pz? e.g. RTU -73 + all other AHUs - 34. the total is 107 which is the actual Pz for this project.
However, doing that calculations, i passed IEQp1 requirements but no to IEQc2, where do i need to adjust? Is it to my CFM values under single zone or multi-zone?
thanks so much again.
Susan
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
April 30, 2012 - 7:25 pm
Hi Dylan,
another thing, do we need to report both cooling and heating mode. Initially, we submitted the cooling mode only, the the reviewer is asking to perform the worst-scenario during heating mode. Now if we're going to submit it for appeal - should we present the heating mode only or both?
thanks,
Susan
Dylan Connelly
Mechanical EngineerIntegral Group
LEEDuser Expert
472 thumbs up
May 1, 2012 - 8:03 pm
Susan,
Ps (without diversity) = Pz total all zones in a system.
Ps (with diversity) should be within 10% of your FTE (+ transients depending on the situation).
If you are not passing IEQc2 then you need to adjust your inputs. Either, increase your total supply OA CFM or find your critical zone (the one with the highest Zp) and increase the Ds (these changes need to be reflected in your design). Do this for each system until you pass.
You only need to report on your worst case mode. This is usually your heating mode. This is because your heating mode usually has a Ventilation Effectiveness (Ez) of 0.8 and a lower Zone Primary Air (Ds) than in cooling mode.
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
May 2, 2012 - 1:54 pm
Dylan,
I still don't understand. The logic behind (D) is it should be equal or less than & aligned to FTE (= 11) and not to Pz total for all zones in a system (73 + 34 = 107)? Is this always factor @ 10%? Can we increase it?
This is what i did: 73/78*100 = 93.5%, my Ps (with diversity) is 73 (which is equal to RTU-1), then if i add other 34 (from other RTUs), the total is 107 which is equal for Ps (without diversity). I also increase OA design to 200 cfm and i passed both IEQp1 and IEQc2. Is this the right approach? Or i need to go back to 10%?
Please clarify again.
thanks - susan
Dylan Connelly
Mechanical EngineerIntegral Group
LEEDuser Expert
472 thumbs up
May 2, 2012 - 4:14 pm
Maybe the 10% is the confusing part. I was simply saying that the LEED reviewer wants to see your Pz within +/- 10% of the FTE (depending on the project type the FTE total would include transients).
You should not go back to 10% for your D value. You should keep it as your D percentage as stated above.
susan eguia
LEED Coordinator/Construction Administrator/Business DevelopmentBuilding Solutions Group, Inc.
59 thumbs up
May 3, 2012 - 8:12 pm
Hi Dylan,
Appreciate your being patient with me.
The following is my additional Qs:
1. what is the equation for Occupancy Diversity (D), i tried to check it from ASHRAE 62MZ LEED guidelines but can't see it.
2. if we still use 10% for D, and our FTE is 11 + 89 transients, then definitely this is not accurate.
3. Can we submit our appeal in different approach - V4.0 for multi-zone since we passed for IEQp1 and ASHRAE 62MZ for IEQc2?
3. Or can we resubmit it using ASHRAE 62MZ, but this for system with critical zone only, right?
Thanks,
Susan
Manny Iglesia
LEED BD+C O+MCarde Ten Architects
121 thumbs up
May 7, 2012 - 6:04 pm
Susan,
Q1: D= Ps/Summation of Pz (all zones) Page 6-24 of ASHRAE 62.1 2007.
Q2: If you got denied using 10% variations,and you still want to use it, then provide a narrative explaining why do you insist. Line item#20 on "Directions" tab of your downloaded 62Mzcalc explains this.
Q3: You can try that. It's up to the Reviewer to decide if you'll get one or both.
Can you not just increase your OA design and avoid using two supposedly similar calcs?