I have done several energy models over the last few years using Trane
Trace. I have heard others (typically from those who don't have
experience with energy modeling) say "it only takes a day" to create an
energy model and get results.
I am trying to get a better understanding of how long it takes others to
complete an energy model. I realize there are many factors involved and
length of time can vary drastically given the complexity of the project.
For an xxx sq ft project with xxx systems:
1. What phase are you starting the energy model - SD, DD, CD?
2. What information are you starting with - load results from another
program, rules of thumb for system sizing, etc?
3. What program are you using?
4. How long does it take to build the proposed model?
5. How long does it take to build the baseline model (per ASHRAE
90.1-2004, Appendix G)?
6. How long does it take to calculate the results from the energy
simulation program?
7. If you have started a projected in the SD phase, how detailed is the
input information you use? How do the results compare to the energy
model developed in CD - within 10%?
Any information you can provide would be helpful.
Thanks,
Sherie Hensley
1. In my perfect world preliminary energy models get built during SD phase
to assist the entire team with design decisions. What I normally encounter
is either a model done after the building design is set but the MEP systems
are still in flux or worse projects that were completing CDs and decide they
need to run energy models to get LEED certification.
2. I think the complexity of the model depends on the stage of a project.
Models started in SD are usually very generic and not very details. As the
design progresses so does the detail of the model.
3. I use Trane Trace
4. It depends on the stage of the project it is started in and how much
duplication of spaces can occur for a large building.
5. I have found that the baseline model can be built very quickly as long
as you already have library members that cover the ASHRAE standards.
6. I have had run times of several minutes to several hours depending on
the size of the building and whether or not full year weather is required.
I have found out that Trace runs 5 to 7 times slower when using full year
weather. Because of this when doing LEED models I use part-year weather
data until I get to the end and start working on data that will be sent to
USGBC.
7. I use basic information, overall square footages, window percentages,
etc and the same type of generic information for the building systems as
well. I have had it vary wildly, but this is a function of models that
start in SD phase have a lot of stuff change between the initial SD models
and the final models.
Thanks,
John Mathews, PE, LEED AP
See below
Yury Lui, PE, LEED(r) AP, CEM