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Re: [EnergyPlus_Support] URGENT: LEED- Cooling Unmet Hours - ASHRAE 2010 - Heated Only Storage - System 9 or 10



I agree with Jim. 90.1 defines unmet load hour as "an hour in which one or more zones is outside of the thermostat setpoint range". It never referes to confort. In this case it is a heated only warehouse, then  I believe  both proposed and baseline models should reflect exactly that.

 

I agree with Jean that comfort should be considered.  However, defining â??comfortâ?? is not exactly a science (or even compliant with ASHRAE Standard 55) when the client agrees to forego air conditioning.  Essentially, they are telling the designer that 90F / 32C is acceptable comfort for their building and its purpose.  We always define â??comfortâ?? for a LEED / ASHRAE 90.1 model to be the same as the Ownerâ??s criteria for heating / cooling temperatures.  A recent project maintained the warehouse in the winter at 55F / 13C, so thatâ??s how we modeled it.

p.s., Another aspect of this is that different countries have differing comfort sensibility than North America.  e.g., USA, India and Germany probably all feel differently about â??comfortâ??.

 

 

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Monday, August 04, 2014 10:15 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] URGENT: LEED- Cooling Unmet Hours - ASHRAE 2010 - Heated Only Storage - System 9 or 10

 

 

I would go a step further and say 1) I aggree with Jim, but 2) the hours of discomfort should be considered (investigated), because the reason that ASHRAE 90.1 App. G included the requirement to model the missing system was to include for when the building gets retrofitted with the missing system because things are just so bad comfort wise. Therefore, in closing, setting the thermostats so that the missing equipment never jumps on is a long time accepted "method" by LEED reviewers, but to stay credible you should prove that the design will produce acceptable comfort levels in the statistical year (put your money where your mouth is). This is in fact what you have to do when you use multi-node bulk airflow simulation methods for IEQ credit (if you use that path) for natural ventilation.

 

2014-08-04 13:31 GMT+02:00 Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx>:

 

Jeremiah,

This has been discussed in the past on this forum and it seems that a number of us include a cooling system, but use a zone setpoint that effectively keeps cooling from turning on.  I see that you are referring to another part of 90.1, the Energy Cost Budget, rather than Appendix G.  Itâ??s language is similar, however.

(90.1-2010 Table G3.1 1b)  All conditioned spaces in the proposed design shall be simulated as being both heated and cooled even if no heating or cooling system is to be installed. Temperature and humidity control setpoints and schedules as well as temperature control throttling range shall be the same for proposed and baseline building designs.

Exception: Spaces using Baseline System types 9 and 10 shall not be simulated with mechanical cooling.

 

My logic has been this:

·         The minimum goal of Appendix G and USGBC is for the Proposed building to use 5% less energy annually than a fictitious â??Baselineâ?? building.

·         If we add cooling energy where none will exist, and assume that cooling adds 30 - 50% to the annual energy. The comparison becomes completely skewed away from the actual buildingâ??s energy use.

 

Why does it make sense to say weâ??ve saved energy with a number that has no bearing on reality?  Perhaps ASHRAE 90.1 allows, or even expects this skewed value, but I feel it does a disservice to our credibility as modelers.  Of course, it may result in less LEED points, too?¦..

 

 

 

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Monday, August 04, 2014 3:14 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] URGENT: LEED- Cooling Unmet Hours - ASHRAE 2010 - Heated Only Storage - System 9 or 10

 

 

My understanding of ASHRAE 90.1 indicates that you can not simply turn the thermostat way up or off. I think what you need to do for your model is to use a theoretical system per ASHRAE 90.1 requirements, eg a packaged single zone air cooled system.  I have included some images below that may help. 

 

Do you have a copy of the standard and users guide? If not you should most likely get yourself a copy. 

 

 

Inline image 1

 

Inline image 2

 

Inline image 3


 

 

â??â??

Jeremiah D. Crossett  | Senior Analyst  | LEED Green Associate 

â??â??

120 E. Pritchard St.  | Asheboro, NC 27203 

â??â??

 | Mobile 503-688-8951

www.phasechange.com 

  

 

 

 

 

On Sun, Aug 3, 2014 at 11:01 PM, hisham.rashrash@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

Dear Santiago,

Many thanks, can you please show me a snapshot of where this option is in DB? I am using detailed HVAC mode, is this option valid for this mode also?

 

If I am following this correctly, does it mean that setting a very high cooling setpoint also solves this problem and unmet hours will be zero for these spaces?

 

Your help is appreciated.

 

Hisham

 

 



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Posted by: Santiago Velez <santiagogvelez@xxxxxxxxx>


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