[Bldg-sim] Modeling fume hood exhausts

[Aleka Pappas]

  I just spent a while digging through all the latest docs on modeling 
labs for a LEED analysis (90.1-2004, 90.1-2007, addenda, & Labs 21).  
This is my interpretation:

    * If the /building/ has fume hood exhaust over 15,000 cfm, the
      Baseline system is VAV, and exhaust is turned down to at least 50%
      for unoccupied hours.  I am modeling the unoccupied turn down rate
      the same in the Baseline as in the Proposed models, because how
      low it can go at night depends on the type of lab (ie: the project
      doesn't get more credit for turning down to 20%).  This is from
      Labs 21, and 90.1 (2004 or 2007) section 6.5.7.2.
    * A project can claim energy savings for demand controlled fume
      hoods during occupied hours if the controls are automatic (Labs21
      has some schedules for guidance in modeling this).
    * Energy recovery is not modeled in the Baseline (see 90.1-2007
      G3.1.2.10 Exception h).

Let me know if you have a different interpretation....I don't think all 
these issues are laid out in detail for modelers yet.

*Aleka Pappas*
Building Energy Engineer

*ENERMODAL ENGINEERING, INC.
*/Inspiring energy and resource efficient buildings./*
**www.enermodal.com*
1325 E. 16th Ave.
Denver, CO 80218
APappas at enermodal.com
Office: 303.861.2070/ Direct: 720.221.1082


On 8/31/2010 12:35 PM, varun kulkarni wrote:
> I think it also depends on the software you are using to model a fume 
> hood. Because if exhaust is specified more than the supply  due to the 
> hood, the software  may disregard the lower supply and equate the 
> higher value of exhaust to the supply. I am also trying to  model a 
> VAV exhaust fume hood and facing a lot of problems doing it. So you 
> have to figure out a way to control you exhaust by altering your VAV 
> supply.
> If you know some other way, please let me know also :)
>
> On Tue, Aug 31, 2010 at 2:23 PM, Sami, Vikram 
> <Vikram.Sami at perkinswill.com <mailto:Vikram.Sami at perkinswill.com>> wrote:
>
>     I think that depends on the total volume of exhaust. I don't have
>     it in front of me, but I think if your exhaust is more than a
>     certain amount you have to have either energy recovery to fifty
>     percent or vav flow.
>
>     Sent from a mobile device
>
>      -----Original Message-----
>     From:   Peter Simmonds [mailto:peter.simmonds at ibece.net
>     <mailto:peter.simmonds at ibece.net>]
>     Sent:   Tuesday, August 31, 2010 12:09 PM Central Standard Time
>     To: bldg-sim at lists.onebuilding.org
>     <mailto:bldg-sim at lists.onebuilding.org>
>     Subject:        [Bldg-sim] Modeling fume hood exhausts
>
>     Can anyone tell me when modeling a lab system with fume hoods as
>     to whether the baseline systems are to be modeled as constant volume?
>
>     (subsequent alternatives will have variable volume fume hoods).
>
>
>
>     Peter Simmonds,Ph.D.
>     Senior Associate
>
>     IBE Consulting Engineers
>     14130 Riverside Drive, Suite 201
>     Sherman Oaks, CA 91423
>     p: (818) 377-8220 x246 f: (818) 377-8230
>
>     www.ibece.com <http://www.ibece.com/> <http://www.ibece.com/>
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> -- 
>
> Thanks and Best Regards,
>
> Sincerely,
>
> Varun Kulkarni , M.S. , EIT
>
> RMF Engineering
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