[Bldg-sim] EUI calculation using ECB Method and PRM Method

[Matutinovic, Luka]

I would agree that, if the goal is to generate a realistic predicted EUI, there isn't much difference (or value) in choosing ECB or App G since you're not really after a baseline comparison. Focusing on determining  the most likely occupancies, schedules and how the building systems will be operated is probably the best approach when trying to predict actual energy performance. Since I think we all agree on how difficult this can sometimes be, educating the client about factors which can negatively impact performance (and hence qualifying your predictions) is a good course of action.

Maybe this goes without saying, but tenant loads and actual sequences of operation play as big, if not a bigger, factor in actual EUI, than the spec'd performance of systems (this is been the biggest lesson learned from our work with benchmarking existing buildings and retro-commissioning). In general, we have found that tenant loads are 1.5 - 2 times higher than ASRHAE defaults and a lot more if there are server rooms (even small ones). You can also usually chalk up a 10-20% increase in EUI from the "ideal" simulation results (using typical schedules and optimal operation of systems) due to changes during construction, lack of completely detailed sequences of operation, incomplete commissioning, tenant demands on schedules and set-points, and general operational "drift" that building undergo over time.

If you are in fact looking at comparisons, I personally think normalized, absolute metrics like cost and energy intensities provide more value to owners, tenants and operators compared to % savings. Benchmarking predicted performance against something like the EnergyStar Portfolio Manager is an interesting and valuable exercise.

I'm looking forward to hearing what others think about this and hearing what experiences are like out there.

Happy predicting,

Luka Matutinovic, P.Eng., LEED(r) AP BD+C
Halsall Associates
Tel: 416.644.0649 * Toll Free: 1.888.425.7255 x 317 *  www.halsall.com<http://www.halsall.com/>
Vancouver * Calgary * Sudbury  * Burlington * Toronto * Ottawa * Dubai
Best Workplaces in Canada, Six Consecutive Years: 2007 - 2012
___________________________
A Parsons Brinckerhoff Company
P Please consider the environment before printing this e-mail

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Erickson
Sent: Friday, June 08, 2012 1:12 PM
To: Arpan Bakshi; Shanta Tucker
Cc: bldg-sim at onebuilding.org
Subject: Re: [Bldg-sim] EUI calculation using ECB Method and PRM Method


Shanta/Arpan,

Forecasting an EUI with energy models is a risky proposition to begin with, though many of us are asked to do so on a regular basis.  Hopefully all modelers realize that modeling is best used for making relative comparisons rather than predicting absolutes.  That said, a model can give you a much better idea of an EUI for a particular building/program than just pulling a value from the air.  Hopefully folks are looking to benchmark data to help confirm the reasonableness of their findings.


To your point about which to use, ECB or Appendix G, I would say neither.  If you're trying to determine EUI it should be based on the most representative model you can develop, not necessarily restricted by anything dictated by 90.1.  To Arpan's point about tracking cost intensities, that makes sense if LEED is part of the project or the owner is concerned with cost.  As engineers/analysts we should be thinking about energy and cost, and in some cases CO2e as well.  The final decision making metric very much depends on the goals of your client.

The challenge on many projects is a tension between energy and energy cost savings.  We have countless projects that save significant amounts of energy but score terribly in energy cost savings (using 90.1 or not as the reason to look at cost), especially with low gas prices these days.  This highlights the importance of the client's goal...if it's about saving energy, the necessary design strategies to do so may or may not also save a proportional amount of energy cost.  Thus the conundrum, energy cost as a metric is not indicative of the energy savings potential of a design path, but it is likely indicative of the likelihood for strategies to provide an economic return on investment.



Shanta, we've seen that it's good to use 90.1 App G for code and LEED modeling, and keep track of those Base and Proposed EUI's, but also consider the EUI of a "typical baseline" design that the owner/market would build and a "proposed" model that is as reflective of our actual design as possible.  It's a lot to track, especially when you add in the cost numbers for each, but it allows us to paint a more complete picture of the options and their outcomes.



Not sure if that resonates with others but would be interesting to hear what others are doing if something different.



Paul

Paul Erickson  LEED(r) AP BD+C
Sustainable PRACTICE LEADER



AEI | AFFILIATED ENGINEERS, INC.
5802 Research Park Boulevard | Madison, WI  53719

P: 608.236.1112 | C: 303.859.7523
perickson at aeieng.com<mailto:perickson at aeieng.com>  |  www.aeieng.com<http://www.aeieng.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]<mailto:[mailto:bldg-sim-bounces at lists.onebuilding.org]> On Behalf Of Arpan Bakshi
Sent: Friday, June 08, 2012 9:19 AM
To: Shanta Tucker
Cc: bldg-sim at onebuilding.org<mailto:bldg-sim at onebuilding.org>
Subject: Re: [Bldg-sim] EUI calculation using ECB Method and PRM Method


In our work we are also leaning towards using cost intensities based on a model rather than energy intensities to "LEED-proof" our early design comparisons.


Arpan Bakshi, LEED AP BD+C

On Fri, Jun 8, 2012 at 10:14 AM, Shanta Tucker <shanta.tucker at atelierten.com<mailto:shanta.tucker at atelierten.com>> wrote:
Hello modeling community,
I've always thought that when trying to forecast an EUI for a building with a whole building energy model, the better approach would be to use 90.1 appx G PRM over Section 11 ECB. While I realize that neither one is intended for energy use predictions per se, I am curious what folks think about using Section 11. Thoughts? Pros/Cons?

Thanks,

Shanta Tucker, PE, LEED AP BD+C, BEMP
Associate

Atelier Ten
Environmental Design Consultants + Lighting Designers

45 East 20th Street, 4th Floor
New York NY 10003
T +1 (212) 254 4500 x210<tel:%2B1%20%28212%29%20254%204500%20x210>
F +1 (212) 254 1259<tel:%2B1%20%28212%29%20254%201259>
shanta.tucker at atelierten.com<mailto:shanta.tucker at atelierten.com>

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


_______________________________________________
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<mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20120608/099e8f28/attachment-0002.htm>