[Bldg-sim] One model

Ravi Srinivasan ravi.s.srinivasan at gmail.com
Thu Mar 12 07:52:06 PDT 2009


Hi All,

Excellent study assessing commercial programs that have integrated solar
gain and daylighting is already available for those who would like to learn
more. Several programs were validated through experiments under the IEA's
SHC Task 34 / ECBCS Annex 43 Project C, titled "Empirical validations of
Shading / Daylighting / Load Interactions in Building Energy Simulation
Tools," (August 2007).

A short version focusing only on EnergyPlus & DOE-2.1E is also available in
Energy 32(2007): 1855-1870, Loutzenhiser et al., "An empirical validation of
the daylighting algorithms and associated interactions in building energy
simulation programs using various shading devices and windows," Elsevier
Ltd.

Needless to say, commercial programs with integrated daylighting algorithms
should be able to simulate, within a certain confidence level, various types
of shading devices (internal / external; venetian / mini-blinds), glazing
types (wavelength selective), light shelves / wells, dome fenestration and
double-skin facades. Until then, it is best to use separate specialized
programs if you are concerned about rich, quality data.

Best regards,

*Ravi Srinivasan**
*LEED® AP, Certified Energy Manager (CEM) & Trainer
BArch, MS(Engg), MS(Arch), Assoc AIA

Silpa Inc.
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AMERICAS   |   MIDDLE EAST   |   ASIA
www.silpainc.com

SILPA VISION
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strengthening and sustaining forces that will reinstate environmental
balances, reinforce natural co-existence and invigorate health, well-being
and economic prosperity.


On Thu, Mar 12, 2009 at 9:56 AM, Michael Donn <Michael.Donn at vuw.ac.nz>wrote:

>  Hi All – again
>
>
>
> When I created my long post on the Daylighting models I self-edited because
> it was looking like going on forever. For example, I stopped short of
> listing the full range of software that has been subject to validation
> exercises, and stuck to just those that have been validated against measured
> data. There is for example the validation suite created by the CIE to be an
> equivalent for lighting of the IEA BESTEST / ASHRAE 140 validation process
> for thermal simulation programs. To my knowledge, AGI 32 and the Integra
> software from Japan have undergone this validation process.
>
>
>
> This most recent post returns our focus to energy simulation. I have over
> the past six months of a sabbatical at the Lawrence Lab in Berkeley CA come
> to know and appreciate the COMFEN program which is targeted at providing the
> power of the EnergyPlus program, very early in the design of a building.
> Programs like EnergyPlus have inbuilt engines for calculating light
> distributions due to daylight. The COMFEN (
> http://windows.lbl.gov/software/comfen/2/index.html ) program from LBNL
> makes some of the daylight calculations within EnergyPlus accessible in
> these very early phases of the design process. This is fully integrated.
>
>
>
> Clearly an add-on for daylighting to a thermal simulation program will not
> be the best lighting program. However, it should be sufficiently accurate
> for many purposes where thermal and daylight performance are combined.
>
>
>
> Rob, you are correct about the su2rad/OpenStudio plugins for SketchUp.
> Because the OpenStudio plugin from DOE/NREL will read EnergyPlus input (idf)
> files, SketchUp is the potential integrator of COMFEN/EnergyPlus and
> Radiance. It works well here because of the elegance of the underlying
> template for the COMFEN EnergyPlus model. But even here it has limitations.
> The thermal simulation model representation of a wall is a set of 3D
> coordinates locating a surface in space and its orientation to the sun. The
> thickness and thermal properties are represented mathematically. Reading an
> EnergyPlus ‘.idf’ file into SketchUp reveals windows with no frame and
> reveals with no depth – anathema to the good daylight modeler. If one
> creates buildings with depth for daylighting in SketchUp, one needs to
> specify thermal zones within the model before exporting to EnergyPlus.
>
>
>
> The single BIM model that links to all analytical programs but is
> independent of them all is an ideal that has been worked on since the days
> of the COMBINE project in Europe 20 or so years ago. Many are working still
> on it. Logic suggests it is the most elegant solution to the dilemma of
> exchange of information between many different analytical programs. But this
> simple illustration suggests to me that the Building Information Model is
> not SketchUp. It is merely one on a long line of geometry creation tools. It
> is unusual in that it can be used to create lighting, acoustic or thermal
> models. But it merely creates a common starting point for these separate
> analytical tools.
>
>
>
> M
>
>
>
>
>
> Michael Donn
> Director Centre for Building Performance Research
> School of Architecture
> Victoria University      +64 4 463 6221  work
> PO Box 600              +64 21 611 280  mobile
> Wellington                +64 4 463 6204  work fax
> New Zealand             +64 21 611 594  mobilefax
>
>
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Rob Guglielmetti
> *Sent:* Thursday, 12 March 2009 4:12 PM
> *To:* Ross Harding
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] One model
>
>
>
>
>
> On Mar 11, 2009, at 6:09 PM, Ross Harding wrote:
>
>
>
>   The ultimate goal for us would be to use one model for daylight and
> energy models, but I haven’t found that quite that simple as most software
> requires varying drawing techniques.
>
>
>
> Amen brother!  Another issue is that while the energy model has to include
> the total building -- all spaces and systems -- to be a complete picture of
> the energy use, a Radiance-based daylight model does not necessarily require
> all the spaces to be modeled simultaneously.  Indeed, the accuracy of the
> ambient calculation is directly affected by the maximum size of the scene,
> and so conducting a simultaneous daylight simulation of an entire building
> at an acceptably rigorous ambient resolution can be -- is generally --
> time-prohibitive.
>
>
>
> As mentioned in a recent thread on this list, Thomas Bleicher's "su2rad"
> plugin for SketchUp can export a SU model to Radiance format and there is
> also an E+ plugin to allow one to use the same SU model for E+ analysis; in
> theory, these three components (SketchUp, su2rad and the E+ plugin) allow
> for a "single model" approach to energy and daylight modeling. However,
> because the su2rad exporter wants to take the entire model and create a
> single Radiance scene description, that creates the aforementioned problem
> of the ambient calculation getting out of hand fairly quickly.  I suppose
> through intelligent layering and model structuring, one could create a model
> that could be exported to Radiance in "space components", but I'm not sure
> if this is compatible with the E+ plugin's layering/model organization
> requirements.
>
>
>
> - Rob Guglielmetti
>
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