We are modeling a building that is separated into three different spaces. These spaces have differing functions, schedules and systems. There is an office, manufacturing area, and warehouse storage.
These 3 spaces combine to over 200,000 square foot, which would make our baseline system a chilled water system. However, it would behoove the project if we could separate out the 3 differing spaces and build a baseline system for each space to compare to. This would put each 'space' in the baseline building under 200,000 square foot and thus allow us to compare our proposed building model to 3 separate systems conditioned by System 3 or 4.
Since each oif these spaces is a minimum of 40,000+ square foot, can we use exception A in G3.1.1? Therefore the baseline and proposed buildings would each have 3 separate systems? If not, could we at least use exception B making them single zone constant volume systems?
Any help would be appreciated greatly. Thanks in advance.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 1, 2012 - 9:42 am
First you enter Table G3.1.1A based on the square footage of the predominant condition (largest sf). You then apply any of the exceptions under G3.1.1.
G3.1.1 exception A only applies for the examples cited unless you can provide some similar justification. You can apply the other exceptions if you can demonstrate that the requirements within them apply.
Wes Lawson
Mechanical EngineerBala Consulting Engineers
4 thumbs up
October 1, 2012 - 10:11 am
Marcus,
The listed exceptions I see only differentiate heating source and residential/non-residential.
We would be differentiating a storage warehouse (only heated) and manufacturing plant (running 24x7 with large machinery) from a standard 40+ hour office. Do you have any experience with this? I would think that it meets the spirit of the rule, even if not clearly defined.
We are hoping to use the baseline based off of the 100,000 sf office (with the 50,000 sf warehouse and manufacturing areas) rooftop units in lieu of a chiller plant.
Any suggestions on how to do so and whether or not it would be agreeable to the USGBC would be great.
Thanks in advance.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 1, 2012 - 10:57 am
Exception B lists differences in thermal loads and schedules. Exception C is related to air flow issues.
Sounds like either one might apply to at least part of your situation. We do have considerable experience with this situation. The reason for the exceptions is to allow secondary systems for significantly difference space types within the same building.
Sounds like the office area is predominant so the baseline is a system 5 or 6. The warehouse and manufacturing area also come in at a system 5 or 6 but exception b or c would likely apply allowing a system 3 or 4 as the baseline.
Another option would be to apply a system 9 or 10 from 90.1-2010 to the heated only spaces.
Steven Er
11 thumbs up
October 2, 2012 - 10:24 pm
Hi Marcus,
Would like to take this opportunity to clarify the baseline HVAC system type selection from Table G3.1.1A.
A footnote from Table G3.1.1A, states "where attributes make a building eligible for more than one baseline system type, use the predominant condition to determine the system type for the entire building". I understand that nonpredominant condition applied to differential of residential/nonresidential or heating source. This mean the use of predominant condition to determine the system type for the entire building is allowed when nonpredominnant condition exists.
In this case, reference to ASHRAE 90.1 2007, IF nonpredominant condition does not exist (nonresidential building and same heating source for all three space), system 7 or system 8 shall be applied for entire building, IF nonpredominant condition does exist (ie. storage warehouse and manufacturing area), office area here is predominant condition, thus apply system 5 or 6 to entire building and apply exception in G3.1.1 for storage warehouse and manutacturing area if applicable.
Any suggestion?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 3, 2012 - 9:49 am
I had been interpreting the use of exceptions under G3.1.1 like you are suggesting - "use of predominant condition to determine the system type for the entire building is allowed" even if you have spaces that qualify under one of the exceptions under G3.1.1. If you read G3.1.1 it basically says follow Table G3.1.1A except where any of the exceptions apply. So the exceptions must be applied where applicable is the correct interpretation in my opinion.
Exceptions b, c, and d to G3.1.1 can also trigger nonpredominant condition in addition to exception a. So it it not just residential vs non and heating fuel type, it it also schedule, thermal loads, air flows, etc. that triggers an exception.
Mac Dolton
Mechanical EngineerSNC-Lavalin Project Services Inc.
October 3, 2012 - 4:07 pm
Marcus,
My project is very similar to this one. Our predominant space is actually the manufacturing area (73,000 sqft). The office is 60,000 and the warehouse is 50,000 sqft. This would make the office and warehouse both system 3 baseline. Can you tell me if there is an official document I can refer to when submitting our project for review that backs up this interpretation of 90.1?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 4, 2012 - 9:43 am
The Advanced Energy Modeling Guide for LEED contains a summary of this approach.