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Re: [EnergyPlus_Support] Re: Mandating EnergyPlus: Is it the right tool for energy code compliance?
Additionally, e+ offers an autocalc for zone sf and zone volume by default, but allows you to overwrite either or both. A warning is issued should the deviation be larger than a certain percent. This helps for some LEED reviewers.
On 19.08.2014, at 15:32, "Jim Dirkes <mailto:jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
>
> Tommy,
> 1. I recommend moving to Michigan! J Weâ??re more reasonable, even if not as cool?. Youâ??ll love the snow!
> 2. DesignBuilder offers several options for area accounting (center of wall, exterior of wall, etc.), but also offers file imports from gbxml and other formats that should result in very accurate area calcs. Open Studio and Simergy also offer this import option, I think.
> 3. 1 minute sims are overkill unless youâ??re doing a very specialized sim. Nonetheless, AL of your simulations donâ??t need to be at the 1 minute interval. Test carefully at smaller timesteps per hour and use 1 minute only after lots of testing and debugging.
> Below is our internal process for â??Running and Debuggingâ??. Mike Witte from the E+ development team provided most of this, but weâ??ve added our own details? I think it will be helpful!
> Running and Debugging (with thanks to M.J. Witte, GARD Analytics, Inc.)
* Open your newly created and complete IDF file in IDF Editor.
* Select the proper weather file.
* Set the warmup days to >= 25 (BUILDING object).
· Run the simulation for DesignDays only. All normal models and modelers have many little problems that can be resolved without running the model for the entire weather year (and wasting a bunch of time!):
> o You may want to add a couple intermediate weather DesignDay to the normal Summer and Winter DesignDays after getting the simulation working well for Summer and Winter. This is a day in which cooling and heating may occur on the same day and also one where your economizer will experience the trip condition (from full outdoor air to minimum)
> o Itâ??s helpful to include full operation on DesignDays for all scheduled equipment items. Energy Plus treats DesignDays as completely separate from â??realâ?? schedules. In order to see if the systems are working properly during the DesignDay runs, youâ??ll want to make sure everything is ON in your scheduling.
> o Consider making a much smaller â??dummyâ?? SLIM file with enough zones for testing. This smaller SLIM file should run a lot faster and enable faster debugging.
> § The idea is to test small portions of the facility before testing the entire facility. Prove that each of the smaller portions works properly before combining them into a single large model.
> § The â??dummyâ?? file must include correct zone names and quantities.
> § Certain multi-zone systems will need â??doctoring â?? to get the zone / system air balance in line
> § If you are autosizing anything, you may find that, for example, the autosized supply air flow is less than the specified exhaust air flow, causing a system to run at 100% OA continuously. (Supply air flow is small because your â??dummyâ?? file represents a smaller building with less load.)
> o These might also be helpful (but are not tested yet) for models that take a long time to run, even when using the above suggestions:
> § Set Building, Solar Distribution to â??MinimalShadowingâ??
> § Set ShadowCalculation, Calculation Frequency to a larger value than default (say, 30 days)
> § Set Timestep to 2 (perhaps even 1. Accuracy is reduced, but this should help for speed until you are confident that all problems are resolved.)
> § Set ConvergenceLimits, Minimum System Timestep to a larger value (say, 15 minutes. Same caution as for timestep above)
> § It is recommended that you use simple shaped zones, with less surfaces. i.e., make the model zones more "square".
> § As rules-of-thumb, EnergyPlus simulations can be slowed down by many windows, many zones, many windows per zone, many surfaces or many surfaces per zone. By lumping building components together rationally, large models can be simplified and thus run much faster. As Einstein said ? keep it as simple as possible, but no simpler. Large models can bbe simplified to a certain degree without sacrificing simulation accuracy. The techniques to simplify large models have been explained in modeling guides, such as the simulation related design briefs and design guidelines in the <http://EnergyDesignResources.com>EnergyDesignResources.com web site, and implemented in some simulation programs, for example, using standard floor shape and layout, adopting typical zoning patterns, and using floor multipliers to represent standard typical floors with similar characteristics. (â??EnergyPlus Run Time Analysisâ?? by T. Hong, F. Buhl, P. Haves 12/15/2008)
> * Use .rvi files to keep variables organized.
· Start debugging
> o Use the .err file which is created during each run to identify the source of errors. The .err file is almost always very specific about the cause of an error, but is sometimes hard to understand. Read carefully!
> o Review the .svg diagram after getting the model to run without fatal errors using Visio or another .svg file viewer.
> o When debugging, focus exclusively on errors which are noted BEFORE a â??Fatalâ?? error. Everything past that hasnâ??t been fully screened and is likely to be bogus. Although they may give a clue why the fatal error occurred, my experience is that I should NEVER pay any attention to errors listed after a fatal error; theyâ??re meaningless.
> o Pay attention to the Warnings, not just â??fatalâ?? and â??severeâ?? errors. These are occasionally indicative of a problem that, while not preventing completion of the simulation, should be corrected to assure accuracy and improve runtime speed.
> o In rare cases, you may want to turn off the HVAC system by setting availability manager schedules to always be OFF. This may allow a simulation to complete, but with warnings for further diagnosis.
>
>
> James V Dirkes II, PE, BEMP, LEED AP
> <http://www.buildingperformanceteam.com/>> www.buildingperformanceteam.com
> Energy Analysis, Commissioning & Training Services
> 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653
>
> From: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
> Sent: Monday, August 18, 2014 6:09 PM
> To: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Mandating EnergyPlus: Is it the right tool for energy code compliance?
>
>
> Thank you all for your input. It's helping me to realize that perhaps I am not crazy and perhaps it's not so bad... and that maybe IPA really should stand for In (case of) Panic Attack since it's also helping.
> Jeremiah: thanks for the suggestion to post on the BldSim group as well. The fact that you're such a proponent of it makes me think there must be value...and that my eyes aren't yet focused; like one of those 3-D posters that drives me nuts until it appears.
> James: thanks for seeing the small business side of it and that not everyone makes it thru a learning curve alive. I don't think I'd have a problem if we could choose what to use, but we can't and that's that.
> So in response to your suggestions I called around and this is what I learned.
> Our GUI interface (CBECC) mandates a time step of 1-minute. No switching it on & off.
> James in response to :Incentives, for example, are not normally â??Take it or leave itâ??; theyâ??re proportional to savings. A few percentage points either way should not affect the grand total much.
> I wish that were the case here. For example Low Income Housing Tax Credits are worth millions of dollars and are competitive - if you say you will achieve 15% or 17.5% you garner a certain amount of points..14.9% or 17.4% will not cut it and you will be penalized and incur negative points for all projects over the next few years. and you probably are go ing to look for someone to blame. Same with almost all the above code programs here in CA. and we have a saying "No one makes it thru plan check unscathed. No one. Not ever.
> So knowing the 1-minute rule got tips for making it run speedy?
> And in regards to SketchUp and E+: at our class we were informed that it was very likely that our finished model would not match the exact sqftg of the plans
> and this cause an immediate uproar as after the address being correct it is what a plan checker checks next; matching sf. The following emails were between myself and the professor
> Q: It was said that using SketchUp should get us within 5% - 10% of the square footage as shown on the plans and you gave an explanation. Is this true?
> A:As for your question below you are correct. Since you are tracing over the actual drawings you should have all areas covered in the model and be very close to the sq. footage shown on the plans.
> Two additional points.
>
> You would need to find out from the architect if the floor area on the plans is from inside / outside / center of stud, or inside / outside /center of finished wall. All architects and building departments have slightly different rules and methods.
>
> Additionally, like we mentioned in the training, spaces below stairs are not usually counted as livable floor area for a building department, but in energy modeling it is difficult to represent the actual area of a core stair for example when it is compared to the usable area of a core stair. This may require notes from you or a quick call to the building department.
> Thoughts?
> Thank you again,
> Tommy Young
> E3NorCal
> ---In <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx, <<mailto:jim@...>jim@...> wrote :
> Dear Tommy,
> I suspect that the only downsides to EnergyPlus are:
> 1. It almost certainly runs slower than EnergyPro / DOE
> 2. There is a fairly steep learning curve to any sophisticated software
>
> The speed of simulations is gradually getting better and there are an assortment of tips and tricks to help your simulations run faster. I suspect that you can continue doing early design modeling with Energy Pro, and that the final EnergyPlus model wonâ??t differ dramatically. You may also want to re-think the design process so that your parametric evaluations can be done separately from a meeting. There are also parametric tools available from several sources that work with E+; you might investigate those.
>
> The learning curve has been shortened with dramatic GUI improvement in the last few years, but itâ??s still substantial and I doubt thereâ??s a way around it.
>
> Governments tend toward â??solutionsâ?? that are not fully appreciative of the people and businesses they impact ? no big surprise thhere. I rather wonder why they pulled the trigger when one of E+â??s big advantages (modeling some of the complex, newer systems) is not even available due to the CBECC-COM limitations. Thereâ??s a tech committee somewhere in Sacramento that you should talk to!
>
> My opinion, though, is that the assumption that a projectâ??s financial success can be based totally on specific energy performance, is a little crazy. What if you discover an input error that affects results adversely? Does your client want the truth or do they want to game the system? Incentives, for example, are not normally â??Take it or leave itâ??; theyâ??re proportional to savings. A few percentage points either way should not affect the grand total much.
>
> Designing thoughtfully and well is one thing. Thinking that ANY modeling program can duplicate the designâ??s performance is unrealistic. Even simple systems have thousands of variables, and complex systems are worse. I have a colleague who recently gave a talk called â??After the Plaqueâ?? in which he described some of the many issues needed to properly fine-tune a facility AFTER they received a LEED plaque for a complex facility. Far better, I think, to spend time and energy doing M&V than to expect â??perfectâ?? modeling results. The incentives can be substantial for some projects, but the life-cycle savings for actual savings will be much greater!
>
>
> James V Dirkes II, PE, BEMP, LEED AP<http://www.buildingperformanceteam.com/>www.buildingperformanceteam.com Energy Analysis, Commissioning & Training Services1631 Acacia Drive, Grand Rapids, MI 49504 USA616 450 8653
>
> From: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx [<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] Sent: Monday, August 18, 2014 12:29 AMTo: <mailto:EnergyPlus_Support@yahoogroups.comSubject><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@yahoogroups.comSubject: [EnergyPlus_Support] Mandating EnergyPlus: Is it the right tool for energy code compliance?
>
>
> Good evening from sunny CA. I am new to the forum and freely admit to being in over my head but have taken encouragement from reading through the past few years of posts and seeing newbies become active contributors, especially the repsonse from Nick Caton to Jeremiah Crosset in May of 2012...I forwarded the exchange to everyone in my office... we get few pearls of wisdom freely handed out. So..thanks!
> To my question -
> On July 1, 2014, California mandated that EnergyPlus be used for our state's energy code (Title 24) compliance. The switch was flipped and we are no longer allowed to use the DOE-2 program most of us had been using (EnergyPro). I am doing as much research as I can but am realizing that perhaps my modeling days are over - and while I am not that old and I am computer literate; I don't know CAD, SketchUp or OpenStudio all that well..and that's OK by me . Modeling was just something I did to suppport my diagnostic testing habit. As I have scoured the internets for training, tips and what-not-to-do's I found this forum and hope that you can offer your opinion.
> Is EnergyPlus the right tool for Statewide code compliance? I understand it's an awesome and powerful program, capable of modeling advanced technologies, but is it the right tool for the market? The market being contractors and developers who just want compliance? The run times have been over an hour at times and these aren't extremely complicated multifamily projects - I see horror stories on here about a 300 zone supermarket that took 12 hours to run. Another factor mucks it up as well -
> * CA now mandates an integrated design meeting. No problem we've been doing them for a while - but it normally involves me running numerous iterations while I am sitting at the big table with the design team. These are for above-code projects so accuracy in predicting the % over code is paramount..absolutely paramount. as often tax credits and incentives are on the line which means so is my job, backside and reputation if I get it wrong ( not saying the software I am using is accurate - but it's apples to apples) How do I explian to anyone that I've pressed calculate and now we must wait and wait? and........... by the way in CA we cannot yet model below-grade walls or solar thermal, chilled beams or VRF etc, etc (CA has a twist to the E+ interface called CBECC-COM to meet our code and the software code has yet to be written for these things) From the help desk: There is no formally approved workflow for modeling VRF systems in CBECC-Com. We are currently pursuing additional funding that will enable us to include these systems in a future version of CBECC-Com.
So... I am asking the professionals: is EnergyPlus the right tool for the job? or should I be justifiably peeved that it feels like I've been forced to ditch my 60 Mbps connection for a 14k Dial-up modem?
> Your help is greatly appreciated.
> Tommy Young
> CEO
> CEPE, HERS I-II Consultant
> <https://ci3.googleusercontent.com/proxy/QfvzobbBwsZdty25jgzyPIVvdEZB7APZzrWNgJ7K75zZTFq6nSjZp5lrBBrJFRYO173Vur1_ixOAJwfopgRsB1-a7ZIQYpi6EWHALPad=s0-d-e1-ft#http://img21.imageshack.us/img21/695/e3builtforsmall.jpg>>
> 2701 Cottage Way, Suite 9
> Sacramento, CA 95825
> ph: 916.739.9750 ext 304
>
>
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