[Bldg-sim] Ashrae 90.1 - Unmet hours

Vishal Garg vishal at iiit.net
Tue Oct 27 01:01:41 PDT 2009
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Thanks Deepak for pointing this out. If anyone has any other
interpretations/suggestions, please let us know so that the website can be
updated.
Vishal
Head, Center for IT in Building Science | IIIT-H | Research University |
Gachibowli | Hyderabad 500 032
Website: cbs.iiit.ac.in | Tel#+91 40 6653 1125| Fax: #+91 40 6653 1413|
Mobile # +919949990900| Email: vishal at iiit.ac.in


On Tue, Oct 27, 2009 at 1:07 PM, Deepak Agrawal <deepak0agrawal at gmail.com>wrote:

> dear All...
>
> the entire issue with unmet hours has been analysed on my website, on this
> link
>
>
> http://greenbuildinggenie.com/tips/leed-issues/item/15-understanding-total-number-of-unmet-hours-as-per-ashrae-901-
>
> regards
>
> On Tue, Oct 27, 2009 at 10:46 AM, ashu gupta <kce2 at kamalcogentenergy.com>wrote:
>
>>  Dear All,
>>
>>
>>
>> Explanation of Unmet Hours is as follows:
>>
>>
>>
>> *Unmet Hours:*
>>
>> Unmet hours of a building are the summation of the number of hours when
>> the heating or the cooling set point temperature of a zone is not met either
>> by the HVAC system or by the plant.
>>
>> *Understanding/Interpreting/Calculating the number of unmet hours:*
>>
>>    - Unmet hour is for a particular zone when the zone indoor temperature
>>    is higher than the heating or cooling set point specified in that hour.
>>    - The number or the percentage of unmet hours in a building is usually
>>    given as one of the outputs of the simulation.
>>    - Zone wise unmet can also be read from the various output files
>>    provided by the software used for simulation.
>>
>> (Example:
>>
>> Visual DOE: “SS-J System Peak Heating and Cooling Days” report &
>>
>> Energy Plus: Output Variable, “Time Cooling Set point Not met”)
>>
>>    - When two zones are unmet at the same hour, this will count to one
>>    unmet hour for the building.
>>    - When two zones have unmet hours during different non overlapping
>>    times of a day, the total number of unmet hours in that day is the summation
>>    of these unmet hours of each zone. This total for the year should be
>>    considered as the total unmet hours of the building.
>>
>> *Example: *
>>
>> When each zone is unmet in the specified hours as beside,
>>
>>
>>
>> Zone 1 unmet during:                        6          8
>> 14        16
>>
>> Zone 2 unmet during:                        6          8
>> 12        16
>>
>> Zone 3 unmet during:                        7          8
>> 12        13
>>
>>
>>
>> Total number of unmet hours of the building: *7 hrs* and not 12hrs.
>>
>> 6          7          8          12        13        14        16
>>
>>
>>
>>    - When percentage of unmet is specified, than this is the percentage
>>    of total number of hours (1 year- 8760 hours) for which the simulation is
>>    performed (not just the occupied hours)
>>    - As per ASHRAE 90.1-2004, the unmet hours of the total building
>>    should be less than or equal to 300 hours and the difference in the base
>>    case and proposed case should be less than or equal to 50 hours.
>>    - If unmet load hours in the proposed building exceed the unmet load
>>    hours in the baseline building by more than 50, then the size of equipment
>>    in the baseline building shall be reduced incrementally, until the condition
>>    is satisfied.
>>
>>
>>
>>
>>
>> Thanks
>>
>> Ashu Gupta,
>> Project Engineer,
>> Kamal Cogent Energy,
>> Kamal Ratan Chanbers 1st Floor,
>> Opp. GPO, M.I. Road,
>> Jaipur 302001
>> Ph 141 2373185(W)
>> Ph 9251665008(M)
>> kce2 at kamalcogentenergy.com
>> www.kamalcogentenergy.com
>>
>>   ------------------------------
>>
>> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
>> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Rosenberg, Michael
>> I
>> *Sent:* Tuesday, October 27, 2009 9:07 AM
>> *To:* Nick Caton; Crockett, Jim; Kendra Tupper
>>
>> *Cc:* bldg-sim at lists.onebuilding.org
>> *Subject:* Re: [Bldg-sim] Ashrae 90.1 - Unmet hours
>>
>>
>>
>> I think eQuest and any DOE2 based software does report the hours of loads
>> not being met as required by Appendix G. In the BEPS report it gives
>> “PERCENT OF HOURS ANY SYSTEM ZONE OUTSIDE OF THROTTLING RANGE”. My
>> understanding of this number is that it is a percentage of scheduled fan
>> run-time hours, so some calculation may be necessary.
>>
>>
>>
>> *__________________________*
>>
>> *Michael Rosenberg*
>> Senior Commercial Buildings Energy Analyst
>> ENERGY & ENVIRONMENT DIRECTORATE
>>
>> Pacific Northwest National Laboratory
>> 2032 Todd Street
>> Eugene, OR 97405
>> (541) 844-1960
>> michael.rosenberg at pnl.gov
>> www.pnl.gov
>>
>> *From:* Nick Caton [mailto:ncaton at smithboucher.com]
>> *Sent:* Monday, October 26, 2009 8:20 PM
>> *To:* Rosenberg, Michael I; Crockett, Jim; Kendra Tupper
>> *Cc:* bldg-sim at lists.onebuilding.org
>> *Subject:* RE: [Bldg-sim] Ashrae 90.1 - Unmet hours
>>
>>
>>
>> Mike,
>>
>>
>>
>> I appreciate you bringing this up.  This definition drives straight to the
>> heart of defining the issue-at-hand…  Since I kinda presented both sides of
>> the issue at once – I’d like to clarify where I stand regarding what the
>> correct interpretation *should be*.
>>
>>
>>
>> The logic is as follows:  If a modeled year has 8,760 hours, can there be
>> 10,000 unmet load hours?  By strict reading of the standard’s definition
>> below, I would put my foot down stating there can *only* be 8,760, at
>> most.
>>
>>
>>
>> By common practice however, it appears a majority (myself included) sum
>> unmet cooling/heating hours between the zones, even if they should fall on
>> the same modeled hour, against the intent of the standard.
>>
>>
>>
>> My pure speculation (for what it’s worth, as a young EIT) is this practice
>> developed because eQuest BDL reports don’t present the crunched numbers in a
>> way that makes the sum of unmet load hours, as intended by 90.1, easy to
>> determine.  I wouldn’t be shocked to learn other energy modeling software
>> packages generate LEED compliance summaries featuring unmet load hour totals
>> in sync with the real intent of ASHRAE 90.1.
>>
>>
>>
>> If there’s anything I’ve learned from going out on a limb, it’s that I’m
>> sure to learn something whether I fall or not!
>>
>>
>>
>> ~Nick
>>
>>
>>
>> [image: cid:489575314 at 22072009-0ABB]**
>>
>> * *
>>
>> *NICK CATON, E.I.T.***
>>
>> PROJECT ENGINEER
>>
>> 25501 west valley parkway
>>
>> olathe ks 66061
>>
>> direct 913 344.0036
>>
>> fax 913 345.0617
>>
>> *Check out our new web-site @ *www.smithboucher.com* *
>>
>>
>>
>> *From:* Rosenberg, Michael I [mailto:michael.rosenberg at pnl.gov]
>> *Sent:* Monday, October 26, 2009 7:39 PM
>> *To:* Nick Caton; Crockett, Jim; bldg-sim at lists.onebuilding.org
>> *Subject:* RE: [Bldg-sim] Ashrae 90.1 - Unmet hours
>>
>>
>>
>> Nick,
>>
>>
>>
>> Your interpretation is the correct one. According to the definitions in
>> Standard 90.1.
>>
>> *unmet load hour:* an hour in which one or more zones is outside of the
>> thermostat setpoint range.
>>
>>
>>
>>
>>
>> Mike
>>
>> *__________________________*
>>
>> *Michael Rosenberg*
>> Senior Commercial Buildings Energy Analyst
>> ENERGY & ENVIRONMENT DIRECTORATE
>>
>> Pacific Northwest National Laboratory
>> 2032 Todd Street
>> Eugene, OR 97405
>> (541) 844-1960
>> michael.rosenberg at pnl.gov
>> www.pnl.gov
>>
>> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
>> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Nick Caton
>> *Sent:* Monday, October 26, 2009 5:33 PM
>> *To:* Crockett, Jim; bldg-sim at lists.onebuilding.org
>> *Subject:* Re: [Bldg-sim] Ashrae 90.1 - Unmet hours
>>
>>
>>
>> Jim,
>>
>>
>>
>> That’s actually a really good question that I was afraid to ask when I
>> first encountered it – kudos to you!  I’ve currently resolved to follow what
>> others seemed to be doing within and outside of my office:  Sum up all unmet
>> hours for cooling and heating between the zones just as you describe.   In
>> your example, I’d agree that the unmet hours of your 301 zone building total
>> 301.
>>
>>
>>
>> I do agree that this doesn’t seem intuitively to be the intent of the
>> standard, however between what is suggested within 90.1, the LEED handbook,
>> and the LEED credit templates – I honestly can’t see any clear indication
>> either way on which is the appropriate interpretation.
>>
>>
>>
>> I think the appropriate metric for ensuring appropriately sized systems
>> should be something like: “hours of the modeled year in which at least one
>> zone has an unmet cooling/heating load,”  but I think that was avoided by
>> all concerned parties because it’s too wordy!
>>
>>
>>
>> My acting interpretation, again referencing your example, is that all
>> systems of your 301 zone example affecting the zones with unmet
>> cooling/heating hours should have their heating/cooling/overall sizing
>> capacity ratios increased incrementally until the design hours fall below
>> 300 (and/or within 50 of the sum from the other model, depending on your
>> situation).
>>
>>
>>
>> Afraid I’m only really adding to the discussion here without providing a
>> solid answer.  Would like to echo the desire to see anyone’s experiences
>> that would help us know the “right” way to interpret this (in my case,
>> specifically in the context of a LEED submittal).
>>
>>
>>
>> [image: cid:489575314 at 22072009-0ABB]**
>>
>> * *
>>
>> *NICK CATON, E.I.T.***
>>
>> PROJECT ENGINEER
>>
>> 25501 west valley parkway
>>
>> olathe ks 66061
>>
>> direct 913 344.0036
>>
>> fax 913 345.0617
>>
>> *Check out our new web-site @ *www.smithboucher.com* *
>>
>>
>>
>> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
>> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Crockett, Jim
>> *Sent:* Monday, October 26, 2009 4:27 PM
>> *To:* bldg-sim at lists.onebuilding.org
>> *Subject:* [Bldg-sim] Ashrae 90.1 - Unmet hours
>>
>>
>>
>> Ashrae 90.1 (2004) Appendix G3.1.2.2 requires a baseline building to have
>> less than 300 unmet hours.  What exactly does this mean?
>>
>>
>>
>> To illustrate my question:  assume you have a building with 301 zones, and
>> each zone has 1 unmet hour per year.  This gives you a total of 301 unmet
>> hours, and requires you to increase your baseline equipment capacity.  But
>> you could argue that, on average, the building has only 1 unmet hour per
>> year.
>>
>>
>>
>> Have any of you run into this?  Is it addressed in an addendum somewhere,
>> etc?
>>
>>
>>
>> Any help is appreciated.  Thanks,
>>
>>
>>
>>
>>
>>
>>
>> Jim Crockett, P.E.
>>
>>
>>
>> Senior Project Engineer
>>
>> Energy & Carbon Management
>>
>> Nexant, Inc.
>>
>> 4021 S. 700 E., Suite 250
>>
>> Salt Lake City, Utah 84107
>>
>>
>>
>> (801) 639-5603 - phone
>>
>> (801) 266-4786 - fax
>>
>>
>>
>> _______________________________________________
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>>
>
>
> --
> Deepak Agrawal
> Hyderabad, India
>
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