[Bldg-sim] ASHRAE 2012 Energy Modeling Conference Topic for Discussion

[Ellis, David]

Bill, Jim, Dennis, et al

This is a tough nut. In the ESPC or ESCO world, where performance must be depended upon to achieve financial returns, there are understood and controlling processes in what equipment is bought, how it is installed, how it is maintained, how it is operated and expected duty schedule. Contracts are written to reduce uncertainty to the point that in some cases any deviance, in seemly minor matters, throws the performance expectations up for renegotiations.

While weather changes can be adjusted for after the fact (and thus readily understood as a reason for some differences between real and modeled performance), outside of the ESPC/ESCO arena, a design engineer/modeler can make their best fine tuned efforts on construction intent equipment and operations, to be undone by changes in installation, commissioning, operational practices and occupancy that are not under their control, and are frequently difficult to document after the fact.

In the design arena, modeling is a means to assess options on a level plane, and should not be offered as a predictor of actual cost unless that risk is fully evaluated and compensated for (both in labor/risk fees and in the processes to assure changes are documented). There is a real need to fully vet an industry standard approach to identifying the risks (for fair negotiation), and establishing standards in best practices.

Yes, our modeling does inform sequences of operations, as strategies can be involved, and are a combined designer and modeler effort. They do indeed make their way into construction intent documents ... but implementation and ongoing maintenance are another matter.

A calibrated model is an excellent tool for more realistically evaluating operational and systems changes. But here too, the results should be considered as a way to evaluate options on a level playing field, as control over so many variables is out of the modelers scope.

I would encourage the development of collective industry guidance towards understanding these risks and offering clarification on expectations for client informational purposes.

David Ellis
PE (VA, MD, DC)
LEED AP BD+C
CEM
PMP

HDR Architecture Inc
Energy Services Technical Director, NC

1101 King Street, Suite 400  | Alexandria, VA 22314
703.647.7735 | c: 703.343.6758
David.Ellis at hdrinc.com<mailto:first.last at hdrinc.com> | hdrarchitecture.com<http://www.hdrinc.com/markets/architecture>
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From: Bishop, Bill [mailto:bbishop at pathfinder-ea.com]
Sent: Tuesday, September 04, 2012 11:33 AM
To: Jim Dirkes; Dennis Knight; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE 2012 Energy Modeling Conference Topic for Discussion

Jim said most of what I was going to say. Additionally,

*         An energy modeler's task for a new construction project is rarely to accurately predict energy use, but to demonstrate compliance with, and improvement over, code performance.

*         Modelers generally do not fine tune plug loads, occupant numbers and schedules etc. because these are kept identical for determining improved performance over code.

*         Sequence of operations. The modeler is usually not the engineer of record, and should therefore not be dictating the sequence of operations of HVAC/plant equipment. I may provide the mechanical engineer with suggestions on controls strategies and setpoints, and sometimes they are receptive. However, my focus as energy modeler is energy, and not comfort, system complexity or reliability. Regardless, the exact sequence of operations, even if meticulously described in the design documents, may not be implemented, or may be changed many times during the first year or two of building operation.

*         No/poor commissioning of buildings. Buildings designed to be very energy efficient often rely on complex controls for HVAC and lighting systems. Many buildings are not commissioned, and even in the ones that are, commissioning is often little more than verifying that the equipment and controls were installed as designed. The commissioning agent rarely has the time/budget/scope to determine that all control strategies are operating as designed. Also, the commissioning agent cannot change the weather conditions during which the building is commissioned, making it next to impossible to check CHW controls during winter for example.

*         New buildings often go through many changes in operating conditions during their first year or two. New buildings are often in use after hours due to people moving into their new offices, or because they are nice facilities and the demand to utilize them is high.

*         One of the best ways to predict energy performance is data mining of existing building performance. Hopefully, CBECS and other building performance databases will be a big area of focus for our field.

[Senior Energy Engineer 28Jun2012]<mailto:wbishop at pathfinder-ea.com>

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jim Dirkes
Sent: Tuesday, September 04, 2012 10:56 AM
To: Dennis Knight; bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] ASHRAE 2012 Energy Modeling Conference Topic for Discussion

Dear Dennis and BldgSim Community,

1.       I think the tools are absolutely up to the task.  My own practice uses EnergyPlus exclusively, but I know that most of the other tools are based in solid thermodynamic and physical principles - so they start on a solid foundation.

2.       Current best practices is another story altogether!

a.       Keeping in mind that I know only the "Best practices" for my own firm ...

b.      Energy modelers of new construction are normally given scant information.

*   Partly this is due to the owner not knowing exactly how the new facility will be used.

*   Partly this is due to the Owner and Designer not caring about, not appreciating the importance of, or just not needing to gather detailed information about the operation of a building that hasn't been built.

*   Partly it's because "as built" is never "as designed". (Think of fan and pump pressure estimates differing from actual, weather variances, occupancy schedule changes, etc.)

*   The energy modeling community has, it seems, a lot of bright young men and women who are "learning the ropes".  The fact that they are becoming involved is very exciting!  Their education must be broadened, however, in order for them to become effective at modeling existing buildings. It's no longer just theory;  there is a lot of practical, "hands on" activity that is needed.

3.       Inferred above is the host of variables that differ in an actual building's operation from what may have been assumed.  The older the building, the more variations there are!

4.       Most building operators, if they exist within the building as a full time position, are distracted with many other details and spent precious little time optimizing energy performance.  If there is no full time building operator .....

5.       This is a field ripe with opportunity!  The first and hardest task, I think, is to get building owners convinced that the ROI for optimal building performance is better than any of their other opportunities for investing.  The next task is to streamline the process of calibration and identification of opportunities so that they is faster and more economical.

6.       ... and I'd love to expand this discussion during the Q&A period at my presentation on this topic during the ASHRAE Energy Modeling Conference!

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

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Dennis Knight
Sent: Tuesday, September 04, 2012 10:24 AM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] ASHRAE 2012 Energy Modeling Conference Topic for Discussion

I am the Chair of the conference committee for the ASHRAE 2012 Energy Modeling Conference that will be held in Atlanta on October 1, 2 & 3 this year (see link below).  The conference is focused on bringing practitioners, software developers, researchers and facility users together for 3 days of in depth discussion on current modeling software capabilities and current best practices in energy modeling.  I have two questions that I would like to pose to this group to get some feedback to help provider richer content for the discussions planned at the conference;
1. Are the current energy modeling tools available to an energy modeling practitioner reliable enough to allow the modeler to predict a building's actual energy consumption with a high degree of confidence such that an accurate energy target can be established and recommended to the building owner for the new building or a  renovation/retrofit?
2. Are the current best practices of the energy modeling community reliable enough, and well understood by most practitioners, to allow the modeler to predict a building's actual energy consumption with a high degree of confidence such that an accurate energy target can be established and recommended to the building owner for the new building or a renovation/retrofit?

Background for the discussion:
These questions recently came up in a discussion among the conference committee.  It seems that one our colleagues from the UK indicated that in the UK new schools have performed very poorly in comparison with their predicted energy use.

Another comment that was made was as follows:
"Often a building's actual energy consumption is 1.5 to 2 times as much as the results of an energy model that was used to make decisions during design about the building's energy using systems.  Is it the the energy modeling tools or is it the processes used by energy modelers to describe the systems and how they operate in the software? Should energy models be used to "predict" a building's future energy performance or just be used to inform better decisions during design?

I have reviewed a good many models and, almost without fail, I never see a modeler start by writing a sequence of operation and I also never see the sequence of operation used by the modeler make its way into a set of construction documents.

Also, when I am the modeler and I am "calibrating" a model to an existing building's actual energy consumption it is a very iterative process.  I know what things to manipulate in the model to effect demand and what things to manipulate to effect consumption.  I just keep going back and forth until I have a model that you can almost lay its output on top of the building's utility bill history. I also have a good understanding of how the building is actually being operated and maintained - which I hope helps make the model more accurate, but, does that process really give me a better model to make decisions from?"


I invite everyone to please, tell us what you think.
Sincerely,





Link to conference webpage: http://www.ashrae.org/membership--conferences/conferences/ashrae-conferences/emc2012



--
M. Dennis Knight, P.E.
Founder & CEO
Whole Building Systems, LLC
P.O. Box 1845
Mt. Pleasant, SC 29465
Phone: 843-437-3647
Email: dknight at wholebuildingsystems.com<mailto:dknight at wholebuildingsystems.com>
Website: www.wholebuildingsystems.com<http://www.wholebuildingsystems.com>


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