The correct/latest 62MZ & LEED min. IAQ spreadsheet?

The "v2009v4_Minimum IAQ Performance Calculator_v03" allows for calculations for either 62.1-2007 (LEED 2009) and 62.1-2010 (LEED v4).

It can be downloaded here: http://www.usgbc.org/resources/minimum-indoor-air-quality-performance-ca...

Please note, that the USGBC LEED 62MZCalc has been retired and replaced with the Minimum Indoor Air Quality Performance Calculator as mentioned above. While you could still use the 62MZCalc.xls if you have access to the document (and your project is under v2009); it may be more beneficial to use the new performance calculator because it may have useful updates to make the documentation process easier. It also minimize the potential for reviewers to comment on use of an old version for compliance.

Hello,

I am trying to use the "v2009v4_Minimum IAQ pERFORMANCE cALCULATOR_V03" to demostrate compliance with the Prerequisite, however, I does not calculate "Ev" nor it indicates the critical zone for the calculation. I was wondering if I could use the 62 MZCalculator to obteind the correct calculations and include these results in te Minimum IAQ from LEED.

thank you,

Paula,

The USGBC has turned what is supposed to be a ventilation design tool into a "LEED" compliance tool. They have decided that Ev and critical zones are not important for a designer, or a reviewer, to know. Without that information a designer cannot use the tool to improve a ventilation design. The USGBC decided to force several v2009 projects into using tools they developed for LEED v4. The old ASHRAE tool door was closed. It is odd to force such a change on project that are under the same LEED version, but that is what the USGBC decided to do. 

You should continue using the "old" ASHRAE calculator as a design tool, and the new tool only for LEED "compliance." Most people are unaware of how the ASHRAE tool works as a design tool. The following is what I can share with you about how the ventilation tool should be used; with EVs and the critical zone data provided to the ventilation designer.

(I was the vice-chair of EQ TAG when we first developed the prerequisite and credit for ventilation. We was primarily Steve Taylor and Dennis Stanke, with my developing the credit language for them in a way to get it included as part of LEED; a task harder than it have been. The tool was developed by an ASHRAE team that included ASHRAE Fellow Dennis Stanke—he developed much of the original ASHRAE spreadsheet and the calculation method. What I will explain below is how Dennis intended to tool to be used—as I remember it from around 2003 until today; I have used the ASHRAE tool as a design tool when helping mechanical engineers and owners solve compliance with LEED issue—we have never added OA when a ventilation design did not comply with LEED; we simply moved air around between zones..

— Enter your design zone ventilation rates for a system.

— Look for the critical zone, and then look at the difference between EVs for all of the zones. The greater the difference in EVs the more OA you have to provide for the system. 

— Adjust the OAs by taking some of the supply ventilation from a high EV zone and adding that to the lowest EV zone. You should see the critical zone in the system change to a different zone. If not move more supply air over. The difference in EVs will be less. 

— You can continue moving supply air around until you what you feel is a reasonable EV difference. 

— You should be able to reduce the OA in the system to get closer to complying without over-ventilating a system because one zone is driving the OA design more than it should.

— FYI: There will always be a critical zone in a ventilation system. It is simply the zone with the lowest Ev—there will always be one in any system. The term critical means the zone you need to focus on when adjusting ventilation rates. 

Well, I see that I now have 1200 thumbs up. A year ago that was over 12,000 thumbs up. Very interesting. Why did that change so drastically?

Thank you Hernando, now I can see the difference between the outdoor air design and the compliance with LEED, which I believe was my mistake.

Very good advice!

Hello again Hernando,

Now I am trying to fill in the V2009v4_Minimum Indoor Air Calculator for multiple zone systems, because I have one system serving maybe two spaces under ASHRAE 170 or a mix of spaces, some under 170 and others under 62.1.

I can´t discover how to do this...I am trying to find "other" for the space definition but this calculator does not have this kind of space, this way I would include the spaces under 170 like "other".

would you please help me with this,

thank you,

Paula

Hello Paula—

ASHRAE 170 is ACH -based. And ASHRAE 62.1 is CFM-based. So, you need to convert ACH to an equivalent—or nearly equivalent—CFM to use the LEED tool. 

For example: Assume a 10x10x10 square foot space; an ACH for OA of 2. The ventilation works out to 2,000 cubic-feet per hour (10x10x10 x 2); which equals 33-1/3 CFM (2000/60 = ~33.3). The floor are works out to 100 square feet. The CFM per SF (what is used by ASHRAE 62.1 Table 6-1, Minimum Ventilation Rates in Breathing Zone) is 0.33 (33.3/100).

The ASHRAE 62.1 is in two parts that are added together: Rp plus Ra. You need to convert Rp in CFM/Person to an equivalent CFM/SF. You know the space occupancy and the floor area. If there are 10 people in your space (100 SF) then this would equal 0.10 CFM/SF. Now you need to find space in the ASHRAE 62.1 Table (6.1) that has a total OA rate that 0.23 (0.333 minus 0.10). 

ASHRAE 62.1 does not have spaces with a 0.23 CFM/SF Rp. They have 0.06, 0.12 and 0.18 (and one 0.48 space). To get a roughly equivalent space you need to work in the other direction—subtraction one of the Ra value (0.05, 0.12, or 0.18) for the example total Ra+Rp result of 0.333. This means you are now looking for a space type with a greater occupancy rate than you actually have. Assume you decided to use 0.18 as the Ra; then the Rp needs to be 0.153 CFM/SF, or higher. If you do not find a space you think is roughly equivalent then use one of the other typical Ra values (0.06 or 0.12).

If you think you will do such equivalence often, it might make sense to make a spreadsheet out of ASHRAE 62.1 Table 6.1. Have the spreadsheet calculate the equivalent CFM/SF for all the spaces and you can more easily find a match. 

BTW— The conversion of Rp to CFM/SF is what ASHRAE, and the LEED tool, are doing to determine compliance. 

Hello Hernando,

Your response is great,

I am familiarized with ASHRAE 62.1, so, basically the amount of outdoor air indicated through ASHRAE 170 would be the the "Mínimum Ventilation  Rates in Breathing Zone" before the adjustments by air distribution effectiveness and in this special case, for Multiple Zone Systems, the adjustmen by the  System Ventilation Efficiency, is that it?,

I would be great if in future versions of the Mínimum IAQ Calculator in LEED they should incorpórate "other" in Space Category for us to be able to incorpórate other types of spaces, with their own Ra and Rp.

Thank you so much!!

Paula

Paula—

The "Minimum Ventilation Rates in Breathing Zone" is the title of Table 6.1 and the values in the table are what ASHRAE determined would provide the proper ventilation rate in the breathing zone by using a simplified calculation approach. This is similar to what the energy codes did for lighting. Proper lighting design requires photometrics in a space to make sure the illumination levels are roughly even in a space—trying to keep the maximum and minimum illumination levels not to far apart, because the human eye likes evenness of lighting and not high variations between dark and light (like a car's headlights coming at you at night—you lose the ability to see properly). So, ASHRAE's people took the footcandle levels used for good lighting designs, then looked at the lighting used, and then they figured out a wattage value that an energy analysis program could more readily model. (Charles Eley was one of the developers of the wattage equivalence, and he was one of the original people who helped develop the ASHRAE 90.1, as well as California's Title 24, energy codes.

The above simply tries to explain why ASHRAE 170 and 62.1 are different. They are not as different as lighting, but the two standards try to address what is not easy to analyze by having other requirements built into the standard in other places. Table 6-2 in standard 62.1 include Ez values based on how well a ventilation supply delivers air into the breathing zone. As I recall, although it is not in ASHRAE 62.1, the Ez of 0.8 in the table is based on a 40 fpm (feet per minute) supply "jet" of air. 

You need to look at your design for your ASHRAE 170 spaces and find the best fit to model it using the ASHRAE 62.1 tool.

Now, the likely reason that "other" is not (no longer) and option is that the GBCI/USGBC does not want their reviewers making judgement decisions if the "other" you have used is appropriate. That is why we need to find a rough equivalent that takes the reviewer's judgement out of consideration. What I do when completing the LEED Form when I have a space where I am using a odd choice to provide an equivalent space type it to provide a brief explanation in the Special Circumstances text box. That way the review will hopefully not question why a space type, such as Light Industrial (which does not exist in ASHRAE 62.1 Table 6.1) is modeled as a Computer Lab. 

Here are a few things to know about the values in ASHRAE 62.1 Table 62.1.

— Ra, Area OA: 0.06 CFM/SF means low odor/moisture generation; 0.12 CMF/SF means moderate  odor/moisture generation; 0.18 means high odor/moisture generation; and even greater rates for very high odor/moisture generation spaces.

—Rp, People OA: The values are based on MET (Metabolic) Rate which is covered in ASHRAE 55. Low values are for low activity (5 CFM/person is for most sitting). Higher values are higher activity levels (Health Clubs are at 20 CFM/person).

Once you realize what the values in Table 6.1 are intended to address, it make the process of picking an equivalent space much easier. Unfortunately, all of the above explanation is nowhere to be found in the ASHRAE standards which is what LEED Reference Guides do not mention any of it. Where I donated 3000 hours of my personal time to the USGBC to develop LEED I learned much of this from the experts who developed the standards. Out intent was to explain such things in LEED to help designers do a better, and more sustainable, job when designing a building. But the USGBC LEED Department, and the outside paid consultants they paid write the LEED Reference Guides, did not understand the underlying basis of the standards.

I have tried explaining parts of the underlying basis of the ASHRAE standards as I learned them from real experts in the passed. But I think those comments are lost in time; they are hard to find of they are still around. 

Thank you Hernando, this is very clear!

Paula— Your suggestion about having an Other option is something the USGBC could do. They would use a dropdown list to pick from option similar to the landscape water use calculator fir WEc1: Low, Average, High, Very High for area ventilation and people ventilation. Sitting could be used for Low (5 CFM/Person) for Rp. Low Dust/Moisture (0.06 CFM/SF—Office Space) could used for Low for Ra. Of course, the USGCB would have to explain the underlying basis for Ra and Rp, but those are easy to understand with short explanations. You could explain why you chose Other in the Special Circumstance box in the LEED Form. The USGCB could even allow you enter any Ra and Rp values you like so that ASHRAE 170 ACH values could be converted to CFM/SF entered exactly into the ventilation rate calculator.