Out of curiosity do you build your proposed model first or your baseline
model first?
I build my proposed model first. This is the way that I was taught and the
way I learned that makes sense to me in terms of "backing-off" the
performance values to that equal of the baseline values. Or in the case of
different types of HVAC systems I prefer to build the proposed model first
and then do a "save as" to a baseline file to make all the appropriate
baseline input adjustments. This just seems most efficient for my modeling
approach.
What's your approach?
pkg
It depends.
Typically when I use a model for design assistance there is no proposed case - I start off with a baseline. That helps identify potential strategies that will eventually make up the proposed building.
I used to always start with the proposed case but with eQUEST 3.64 it seems
like it will be best to start with the baseline building.
Pasha:
I always start with the baseline model because I am usually hired to provide
design suggestions. By modeling the baseline first I become familiar with the
90.1 requirements for the type of building and systems we are working on and I
can make suggestions that will increase the efficiency of the facility above and
beyond the 90.1 standard.
For example, if my total exhaust air for a zone is less than 5,000 CFM, 90.1
does not require exhaust energy recovery, but by implementing this option in the
proposed model we can achieve a greater reduction compared to the 90.1 baseline.
Paul Diglio
A couple of further questions then:
- if you are doing a LEED (or other) compliance model (without design
analysis) then do you build the proposed or baseline model first?
- With eQuest 3.64 doesn't it create a baseline model file based on
building your proposed model in eQuest first? I thought that was the
function/convenience of the compliance tool. Of course the baseline model
file needs to be checked and calibrated but the general intent was to
streamline the creation of a baseline model file in response to the inputs
for the proposed design. Is this correct logic?
pkg
Pasha:
I have not had the opportunity yet to create a model in 3.64. I tried the 90.1
compliance on a few 3.63 projects and came up with all kinds of odd errors that
I did not research.
The models that I tried were very unusual, for example two sources of exhaust
air and three sources of heating per zone. Naturally, I had to fudge the
systems to model a thermally equivalent mechanical system and work up
exceptional calculations for GBCI.
Perhaps the compliance works well with standard type systems. Do you know if
the compliance in 3.64 will accept a 3.63 project seamlessly?
You might be correct that 3.64 is intended to create a baseline from the
proposed. My initial take was that the compliance tool would compare the
baseline that I create to 90.1 specs and verify if I have modeled this
correctly.
What is your experience? Can you create a baseline model from a unusual
proposed model using the compliance tool?
Paul Diglio
I've gone both ways over time and changed my mind a few times... Here's
my current take:
Whenever the proposed design is available for me to reference, I always
prefer to start with the proposed model and then follow up with the
baseline. The main reason in my mind: the familiarity you gain with the
proposed design (building/systems/loads and so on) by building that
model first really streamlines the creation of a baseline model. On the
flip side and in my experience, starting with a baseline can sometimes
require a lot of cross-referencing to ensure you define zoning patterns
that will work for the proposed design systems. Also, if and when you
may need to calibrate the building loads/scheduling from the library
defaults to match the proposed design systems' anticipated values, it's
easier to calibrate one model and copy that work vs. calibrating two at
once. I personally find it annoying when I am juggling two open models
and editing both when it could have been avoided.
In a conceptual stage of new construction design, my "baseline models"
are more often exploring a select few aspects of design at a time... and
reporting modeled behavior in a relative sense against defined
alternatives, not against a full-out 90.1 baseline. It's pretty hard to
frame a response to a query during a conceptual stage about window
materials as "you'll get 3.2 LEED points with Option A" when you don't
know the rest of the proposed systems/design - or even the building
shape sometimes! I much prefer to address such queries with relative
gains, and advise what will tend towards a better final design. The
advantage to this approach is that time spent coming up with arbitrary
guesses at final proposed/baseline performance can instead be spent
helping guide the various parties towards an ideal final product in a
quick fashion. The disadvantage is we don't typically know quite where
the chips may fall until we are past the conceptual design stages, but
my gut tells me you really can't really know that until ink starts
hitting paper, so to speak.
3.64's LEED analysis feature is intended to streamline the process of
creating a baseline from a proposed model, but it's best summed as a
"feature in progress." At best right now it creates a partial baseline
model - with extra work required to wrap it up. Be cautioned there are
bugs in the current iteration of this tool that may result in getting
nothing for your efforts - don't use this on a project with a tight
deadline until you've tried it at least once.
I would suggest creating your first model to cut your teeth on this
feature from the 3.64 DD wizards. 3.63 models can be cranked through
this tool, but they miss out on a good bit of the streamlining as they
don't have a variety of 90.1 compliance variables defined in the wizards
- I'm not convinced large 3.63-based models really can save much time
from this tool as a result.
Outside of new construction or LEED, the term "baseline model" typically
means something much different from the context of a 90.1 compliant
building - it means what's existing. Those projects by contrast always
involve building the baseline first in my experience.
NICK CATON, E.I.T.
Nick,
sometimes I think you state my thoughts better than I do, or maybe it's just
that we seem to think the same. Great discussion.
Thanks to everyone who is contributing.
There are so many ways to create good, quality energy models. The bottom
line key is that there is no right way, and there is no wrong way--though as
simulators we have to be responsible for all of our numbers & assumptions no
matter which order we input them to create our models. If our results can
be supported and verified through pragmatic approaches and experience with
building design and energy use reference data, then we can feel more
confident that our models are in fact giving us a good (useful) 'glimpse' of
real life operation.
Pasha