[Bldg-sim] BIM

[Jackson, Alan]

I am going to touch on a couple issues that haven't been mentioned yet. 

 

First let me start off by saying that 3rd party software representatives
replying to this thread saying their software works great makes me
cringe a little bit, so any recommendations in that regards should be
taken with a grain of salt. 

 

The underlying issue here is whether or not BIM models should even be
linked to energy models at all. I have done extensive research on the
topic you have brought up and ultimately come to the conclusion that at
this point in time BIM models and their relative analytical loads model
should be independent of any energy modeling that needs to be done
either for code compliance, LEED documentation, LCC etc.  (Just one
thing. The integration of heating and cooling loads inside BIM models is
absolutely amazing and the parametric workflow in Revit works flawlessly
such as auto resizing of outlets, terminals and equipment so I don't
want to confuse the two here)

 

The issue is this. The typical workflow of energy modeling is that
architects define the geometry, programmatic layout and material
selection at which point the building is handed over to the engineers
who design the system and usually also perform the energy modeling do
the complexity of modeling MEP building energy and water systems. The
problem with this workflow is that the geometry, program and materials
are constantly changing and the links from BIM to GBXML or IFC and then
to the energy modeling software is not parametric. Changes that are made
architecturally are not easily integrated into a pre-existing energy
model. Things get deleted and move around and your systems will need to
be re-defined and that's even if the software supports GBXML
"re-importing".

 

The other issue is defining the zones themselves. This is almost
entirely controlled by the architect. In Revit room bounding objects are
controlled by the architect. The ability to merge rooms in into one
thermal zone is an extra step. In fact the whole creation of spaces and
zones is a step that has to be taken, which really means if you are
going to have to fiddle with room bounding objects like walls and
ceiling and the splitting of perimeter zones with space partitions why
not do it from scratch. The geometry portion of an energy model is the
quickest step anyway, (usually). 

 

Then there is the issue of whether or not the software you have used for
years can accept GBXML or IFC and if so how clean does It get imported?
So you may be forced to learn new software (IES or TAS) which may not
even model some important systems like the water-side components or CHP
and power generation as accurately as your tried and true DOE based
software, E+, etc. 

 

I am leaving out a lot here, but you get the point. This isn't cut and
dry and you may find its best to stick with HAP or whatever you are
comfortable using until these issues can get resolved to ultimately
provide a more flexible and parametric workflow. 

 

On the positive side, GBS is a great tool though if you want rough
estimates (SD) on energy use without the detail that other software
provides. It is quick to set up and test ECM scenarios. IES also has
similar "SD" level tools in their IES-Toolkits which offer good early
level analysis components.

 

Alan Jackson, LEED AP
KlingStubbins

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bonafe, Wes
Sent: Thursday, October 08, 2009 8:38 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] BIM

 

Is anyone aware of a good way to get REVIT to report or assist in
reporting building energy use?  We currently use HAP however are not
opposed to purchasing new software.

 

Thanks;

 

Wes

 

Wes Bonafe, P.E.
Chief Mechanical/Plumbing Engineer
Vice President
LEED Accredited Professional

MOSELEY ARCHITECTS 
Architecture. Engineering. Interiors. Planning
3200 Norfolk Street
Richmond, VA 23230
804.794.7555
FAX 804.355.5690
www.moseleyarchitects.com
www.moseleyprojects.com


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