We are working on a project that includes spaces used to manufacture healthcare instrumentation in a clean room environment. The client’s Engineering Standards as well as ISO 14644-1 Standard for Clean Rooms require these rooms to operate with a minimum 25 air changes per hour while meeting comfort cooling and dehumidification for the regularly occupied spaces. According to ASHRAE 90.1(2010) – 2.1, “This standard provides minimum energy efficiency requirements for the design, construction, and a plan for operation and maintenance of new equipment or building systems specifically identified in the standard that are part of industrial or manufacturing processes.” Based on the previous remark, we do not see this as a process or unregulated load. The LEED v4 reference guide defines process energy as “power resources consumed in support of a manufacturing, industrial, or commercial process OTHER THAN CONDITIONING SPACES AND MAINTAING COMFORT AND AMENITIES FOR BUILDING OCCUPANTS OF A BUILDING.” The baseline system for this area is System No. 5 (Packaged DX w/ hot water reheat) where the supply air flow rates are designed based on “the air flow required to comply with applicable codes or accreditation standards” (Appendix G – G3.1.2.9.1) aka 25 ACH. The proposed system is a VAV recirculation unit with a decoupled DOAS unit.
It is important to note, the baseline system could have been our proposed design and would meet all code requirements. Not being able to take savings from our energy efficient design doesn’t seem to make much sense.
The first LEED review stated the following: a clean room application (airflow sized based upon a discharge air to room air delta T much lower than 20 °F (per G3.1.2.9.1) basis for the rooms to maintain a certain level of cleanliness rather than maintain thermal comfort of the occupants). In which case it would be expected that such a system is not covered under ASHRAE 90.1 - 2010 and would be considered a process load like other manufacturing systems. As process systems, the cleanroom systems and all setpoints must be modeled identically in the Proposed and Baseline Cases, unless the exceptional calculation method is used”
Second review stated the following: “25 ACH significantly exceeds the airflow rate for standard HVAC systems designed to meet the needs of human comfort. ASHRAE 90.1-2007 Section 2.3 states that “The provisions of this standard do not apply to” “c. equipment and portions of building systems that use energy primarily to provide for industrial, manufacturing, or commercial processes”. However, ASHRAE 90.1-2010 expand the scope and Section 2 Scope indicates that ASHRAE 90.1-2010 applies to “new equipment or building systems specifically identified in the standard that are part of industrial or manufacturing processes”. ASHRAE 90.1-2010 User’s Manual Chapter 2 Scope clarifies the “Scope of Standard” specifically addressed in the ASHRAE 90.1-2010: laboratories, kitchen ventilation, data centers, and elevator cabs. Future addenda will likely address other manufacturing and/or industrial processes. The HVAC systems serving manufacture spaces are not specifically identified in the standard, therefore, considered as nonregulated energy loads. Nonregulated energy loads must be modeled identically within the Proposed and Baseline Case models unless savings for these items are justified using the exceptional calculation method”
If we would like to attempt to gain some savings from this “process/unregulated load”, we’d need to submit using an Exceptional Calculation Method in comparison with the standard practice for a similar facility. How do we know what is considered “Standard Practice”? Can anyone offer guidance to this approach?
Per ASHRAE 90.1-2010, section G2.5, Exceptional Calculation Methods shall be “used when the simulation program does not model a design, material, or device of the proposed design”. That is not the case for this project as the simulation program can model the proposed HVAC system.
Although we disagree that this should be considered a process load, we offered the suggestion to size the baseline and proposed systems based solely on occupancy and load. The additional airflow would be considered a “process load” and modeled identically in the baseline and proposed scenario. This was not acceptable either.
Any guidance is greatly appreciated!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5900 thumbs up
April 2, 2022 - 2:09 pm
This is very clearly a process load for LEED projects based on long-standing precedents. As the adopting authority, LEED has been interpreting the standard (90.1) in very particular ways. There are many LEED Interpretations on both the process load issue and the exceptional calculation method as they apply to LEED projects.
Standard practice is based on what is done for the typical, similar project in this area. Usually the designers of such system are aware of what is standard practice in any given situation. So in an exceptional calcualtion you simply have to make the case for the baseline that you would like to create for comparision so you can claim savings. You can document a baseline by sharing previous design experience on other similar projects. Sometimes you can find your local utility rebate program has defined a baseline for your area for specific technologies. In other cases you just have to make your case as to why you believe that you are defining an appropriate baseline and the reviewer evaluates whether you have made an adquate case to claim the savings.
Maria Papiez
Director of Sustainable DesignEwingCole
4 thumbs up
April 4, 2022 - 12:13 pm
Thank you for the quick feedback on this, Marcus. I'll share with our team so we can adjust and plan accordingly moving forward.
Cory Duggin
Senior Energy WizardTLC Engineering Solutions
51 thumbs up
April 4, 2022 - 12:34 pm
I previously took savings in a clean room on a LEED v2009 project. It was a little more straighforward because of 90.1-2007 G.3.1.1 exception c included spaces with minimum code required air change rates and special pressurization requirements. That language was removed in 90.1-2010 though to become what is now G3.1.1 exception b. I treated the air change requirement in the clean room the same as I would air change requirements in an OR. You might could even make a case for using exception b to make them constant volume systems in the baseline. Our savings were from using particle counters to reduce the recirculation unit ACH. Then the baseline was constant volume at the design air change rate.
Maria Papiez
Director of Sustainable DesignEwingCole
4 thumbs up
April 5, 2022 - 12:22 am
Marcus, Thank you again for your feedback. In talking with my team's engineers, they would like to follow-up on 2 items.
1) When pursuing the Exceptional Calculation Method (ECM) we plan to show a standard for the baseline system (of the types you noted above). We plan to compare the standard to the proposed HVAC systems (non-regulated loads) that serve our cleanroom. We will perform that comparison using a simulation program (the same simulation program used to show energy savings for the rest of the project). Any issues with this approach?
2) The LEED v4 Reference Guide (page 350 in the big manual) indicates that “ASHRAE Section G2.5 indicates that exceptional calculation methods cannot constitute more than half of the difference (i.e., savings) between the proposed and baseline buildings. However, in LEED, this rule will not be applied to savings attempted on nonregulated loads unless the nonregulated load cannot be modeled in the simulation program.” Given that we are using the simulation program to model our ECM savings, are we capped at half or are we not limited to savings?
Many thanks!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5900 thumbs up
April 8, 2022 - 5:02 pm
1. You just need to justify the baseline system you select as being standard practice in this situation in your area.
2. You are not limited since the savings can be modeled in the simulation program.
Luis Andrade
2 thumbs up
December 1, 2022 - 5:22 am
Hi all,
I've been searching around the Q&A's given about the ventilation of laboratory spaces. However I am still not sure on how to adress some issues. As such, please confirm me if I am doing some considerations correctly or not:
1) The Proposed Design airflow rates are superior of those in ASHRAE 62.1 - 2010 Laboratories (Educational), as they follow industry standards (ISO). In lieu with ASHRAE 90.1 - 2010, section G3.1.2.6, exception c language, does the industry code qualifies as "building official requirements" (and we must apply exception c and therefore 62.1 for Baseline minimum outdoor airflow)? Or may we use in the Baseline the same minimum outdoor airflow as the Proposed Design? In my opinion, a professional (pharmaceutical, rather than an Educational) Laboratory is not listed under ASHRAE 62.1 - 2010 and as such the outdoor airflow of these spaces should be treated and considered the same in Proposed and Baseline buildings.
2) As per ASHRAE 90.1 - 2010 Table G3.1.1A (in the notes), Laboratories spaces Baseline HVAC systems are regulated and, therefore, their associated energy consumption is not considered as "Process Load" and must be modelled accordingly with that table. Therefore, the HVAC systems of the Proposed and Baseline will be different and savings may be claimed with energy efficiency measures.
3) If 1) and 2) are wrong, in total or in part, shall I consider the same HVAC systems, outdoor airflows and energy sources for the Proposed and Baseline (modelling them both iddentically for those spaces)?
Thank you all very much for your time and help!
Tyler Thumma
7GroupLEEDuser Expert
65 thumbs up
December 16, 2022 - 10:19 am
1) Yes, if another applicable code requires laboratory airflow rates which are greater than those required by ASHRAE 62.1-2010, then they may be modeled in the Baseline Case. If the Proposed design includes any additional airflow beyond those code requirements, then the Baseline rates would remain at the code values and would still differ from the Proposed.
2) Correct.