[Bldg-sim] Ashrae 90.1 - Unmet hours

Hernandez, Arturo ahernandez at owpp.com
Tue Oct 27 12:47:03 PDT 2009


This is good to know because I know in the past USGBC did not allow it. I think it makes more sense now that they have gotten the OK from ASHRAE.

 

ARTURO HERNANDEZ, Mechanical Engineering
OWP/P | CANNON DESIGN



 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Gregg Liddick
Sent: Tuesday, October 27, 2009 2:30 PM
To: James D. Waechter; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Ashrae 90.1 - Unmet hours

 

The USGBC received confirmation from ASHRAE that it is OK if the baseline unmet load hours exceed the proposed unmet load hours by more than 50, given that they are both below 300.  

 

Any review comment stating anything to the contrary was written before the guidance was received and it is completely acceptable to reply to the review comment with a comment stating it is OK that the baseline exceeds the proposed by more than 50.

 

Best Regards,

 

Gregg Liddick, EIT, LEED® AP

 

The Epsten Group, Inc.

429 Edgewood Avenue

Atlanta GA 30312

Phone: 404-577-0370  ext. 102

Fax: 404-577-1739

www.theepstengroup.com <http://www.theepstengroup.com> 

 

Please consider the environment before printing this e-mail.

 

This transmission is intended exclusively for the individual or entity to which it is addressed. This communication may contain information that is confidential, proprietary, privileged or otherwise exempt from disclosure. If you are not the named addressee, you are NOT authorized to read, print, retain, copy or disseminate this communication, its attachments or any part of them. If you have received this communication in error, please notify the sender immediately and delete this communication from all computers. This communication does not form any contractual obligation on behalf of the sender, the sender's employer, or the employer's parent company, affiliates or subsidiaries.

 

 

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James D. Waechter
Sent: Tuesday, October 27, 2009 3:26 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Ashrae 90.1 - Unmet hours

 

I'd be very interested to read up on the previous discussions, but a search of the archive didn't turn up much.  

 

90.1-2004, 90.1-2004 User's Manual, and 90.1-2007 all use "exceed" in this sentence.  I don't have a copy of the '07 User's Manual, but even if it does use the phrasing "difference of", I don't see how USGBC can hold anyone to it; it is not written that way in the standard.  End of discussion. (Just my opinion.)

 

James D. Waechter, PE, LEED AP  |  Engineer II 

BEAUDIN GANZE CONSULTING ENGINEERS, INC.

 

P  303.278.3820 x 5246  F  303.278.3843  W  www.bgce.com  

ü Please consider the environment before printing this email

 

 

________________________________

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Hernandez, Arturo
Sent: Tuesday, October 27, 2009 1:00 PM
To: Crockett, Jim; Scott Criswell; Rosenberg, Michael I
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Ashrae 90.1 - Unmet hours

 

I use to agree with the statement and methodology you have provided. However, there have been discussions that definition of "exceed" is the "difference of". Hence making this statement false. In addition the ASHRAE User's Manual also indicates that it is the "difference of" and does not use the word exceed.

 

ARTURO HERNANDEZ, Mechanical Engineering
OWP/P | CANNON DESIGN

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Crockett, Jim
Sent: Tuesday, October 27, 2009 1:28 PM
To: Scott Criswell; Rosenberg, Michael I
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Ashrae 90.1 - Unmet hours

 

It's splitting hairs, but one item in the email from Ashu is not quite correct.  The following sentence is from his email, and the incorrect line is in bold:

*	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.

 

What Ashrae actually says is, ". . .unmet load hours for the proposed design shall not exceed the number of load hours for the baseline building design by more than 50."  

 

If you have a building where the baseline has 300 unmet hours, and the proposed has 0 unmet hours, no correction is needed.  A correction is only needed if the unmet hours in the proposed exceeds those in the baseline by more than 50.  (or if either exceeds 300).  Worded differently, if the baseline has 300 unmet hours, and the proposed system has 0 unmet hours, you do not need to make the baseline more stringent.  

 

 

________________________________

From: Scott Criswell [mailto:scott.criswell at doe2.com] 
Sent: Tuesday, October 27, 2009 10:09 AM
To: Rosenberg, Michael I
Cc: ashu gupta; Nick Caton; Crockett, Jim; Kendra Tupper; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Ashrae 90.1 - Unmet hours

 

I can confirm Mike's understanding of the DOE-2/eQUEST results.  To get the correct number of hours of unmet loads, people should MULTIPLY the Percent hours outside throttling range from BEPS or BEPU by the total annual "hours fans on" listed in report SS-E.

One other comment re: Ashu's write-up - I believe that (for DOE-2/eQUEST) a zone temperature has to be more than one degree outside the throttling range for that hour to be counted as an hour outside throttling range.  So for a zone with a heating thermostat setpoint of 72 and a 2 degree throttling range (=> 71-73 degree "throttling range"), the zone temperature would have to be LESS THAN 70 in order for that hour to be counted.

related info -
We are contemplating a change to the Air-Side HVAC Summary view in the eQUEST interface to report this total number of hours as opposed to just the percent in the totals section at the bottom of the report.
We have also just in the past several days (thanks to the efforts of Steve Gates) added precision to the percent hours outside throttling range reported on BEPS & BEPU and ALSO added separate reporting of hours any zone is either under cooled or under heated, intended for reporting to LEED submission templates.  Assuming no further changes (which is certainly not out of the question), future releases of DOE-2/eQUEST will report the following in the BEPS & BEPU reports:
         PERCENT OF HOURS ANY SYSTEM ZONE OUTSIDE OF THROTTLING RANGE =  4.45
         PERCENT OF HOURS ANY PLANT LOAD NOT SATISFIED                =  0.00
         HOURS ANY ZONE ABOVE COOLING THROTTLING RANGE                =    98
         HOURS ANY ZONE BELOW HEATING THROTTLING RANGE                =    25

- Scott


Rosenberg, Michael I wrote: 

Ashu,

 

I am in agreement with everything you stated except possibly this;

 

"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)"

 

My understanding is that some simulation programs (DOE2 and eQuest in particular) report this as a percentage of hours that the fan is running. I could be wrong, and I am sure some of you DOE2 experts can comment on what is reported in the DOE2 BEPS report.

 

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: ashu gupta [mailto:kce2 at kamalcogentenergy.com] 
Sent: Monday, October 26, 2009 10:17 PM
To: Rosenberg, Michael I; 'Nick Caton'; 'Crockett, Jim'; 'Kendra Tupper'
Cc: bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] Ashrae 90.1 - Unmet hours

 

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 <mailto:kce2 at kamalcogentenergy.com> 
www.kamalcogentenergy.com <http://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

 

 

 

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).

 



 

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

 

 
 
 
 
 
 
 
 
 


________________________________



 
 
 
 
 
 
 
 
 
_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send  a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
  


-- 
This message has been scanned for viruses and 
dangerous content by MailScanner <http://www.mailscanner.info/> , and is 
believed to be clean. 


-- 
This message has been scanned for viruses and 
dangerous content by MailScanner <http://www.mailscanner.info/> , and is 
believed to be clean. 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20091027/089f0cdb/attachment-0002.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 1459 bytes
Desc: image001.jpg
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20091027/089f0cdb/attachment-0002.jpeg>


More information about the Bldg-sim mailing list