[Radiance-general] Finding contribution of different glass roof panels using r(t)contrib

Wed Jul 17 12:46:30 PDT 2013

Sorry for sending a second e-mail, I sent it by mistake.

a1, a2 and etc... are the transmissivities in my example (1 equals air, 0
equals black). But I am not sure if that linear scaling and adding is
valid...?

I am interested to see the solution you use!

THANKS

German

2013/7/17 Germán Molina Larrain <gmolina1 at uc.cl>

> I am not sure if the 3phase method is the best in this case, since the
> accepted basis (145 Klems' division) is not very good for specular
> fenestration systems (such as glazings).
>
> Maybe a possible solution would be to make separate DC analysis for the
> different fenestration groups (i.e. make all glazings black, except the one
> to be analyzed) and somehow scale them by transmissivity...?? I mean:
>
> For each glazing group:
>      - Make every other glazing black, and this glazing with 100%
> transmittance
>      - Calculate DC.
> end
>
> then, the lighting levels would be
>
> Lux= a1*DC1+a2*DC2+a3*DC3...
>
> Does this make any sense?
>
>
>
>
> 2013/7/15 Jack de Valpine <jedev at visarc.com>
>
>>  Hi Reinier,
>>
>> You should probably take a look at the "three-phase method" which breaks
>> flux transfer down into three discrete steps:
>>
>>    1. sky to glazing exterior
>>    2. transmission through glazing
>>    3. glazing interior to built environment
>>
>> Glazing transmission (2) is accounted for via a BSDF representation. The
>> nice thing about this is that if you want to change glass type/performance
>> you do not end up having to re-run a complex simulation, it is a matter of
>> recomputing a matrix calculation. In other words, the material behavior of
>> the glazing is a separate step and does not actually take that long. Andy
>> McNeil has a great tutorial on using this method:
>>
>> http://www.radiance-online.org/learning/tutorials/Tutorial-ThreePhaseMethod.pdf
>>
>> I recently worked on a project using this method. The main goal was to
>> evaluate daylight based on hourly weather data for the locale for plant
>> growth within a selected exhibition environment. Using this approach, was a
>> big help when we needed to look at some other glazing options.
>>
>> This does requires some setup work particularly if you are looking at
>> rooftop glazing. You will also want to think carefully about how far you
>> want to break down the glazing panels, whether individual panels or
>> grouping of some sort.
>>
>> If you are calculating sensor points you may find that you can do it on
>> your workstation, however AWS/EC2 is definitely worth considering as an
>> option. I did use AWS/EC2 for final runs as I did not want to have to wait,
>> however I was generating images...
>>
>> Hope this helps.
>>
>> -Jack
>>
>> --
>> Jack de Valpine
>> President
>>
>> Visarc Incorporatedwww.visarc.com
>>
>> channeling technology for superior design and construction
>>
>>
>>
>> On 7/15/2013 10:53 AM, Reinier Zeldenrust wrote:
>>
>>  Dear all,****
>>
>> ** **
>>
>> I’ve been following some of the discussions on the mailing list with keen
>> interest and gratitude. Now, I’d like to hear your thoughts on something
>> I’m working on. (Hopefully, I’ll be able to start answering other people’s
>> questions soon too!)****
>>
>> ** **
>>
>> I’m working on a building with a large glass roof, with plants and people
>> inside. The goal is to find optimal light transmittances for different
>> parts of the roof so it is relatively uniformly lit throughout the year.
>> The main worry is getting enough light for the plants, yet limiting
>> irradiance to not require excessive cooling.****
>>
>> ** **
>>
>> Here’s what I am thinking at the moment:****
>>
>> ·         Break up dome into N separate panels using Rhino/Grasshopper,
>> assign each panel to a layer, and then export layers as materials using DIVA
>> ****
>>
>> ·         Generate a materials file with N identical materials with
>> material_i as name****
>>
>> ·         Run r(t)contrib for the different modifiers (using –M and a
>> modifier file)  and points, using a cumulative sky generated by DIVA, to
>> find to each point by each panel****
>>
>> ·         Visualise output data using Rhino/Grasshopper****
>>
>> ·         Find (near) optimum light transmittances based on 2-3 criteria
>> (still to be defined, but likely UDI and uniformity). With the available
>> data is should a purely numerical exercise, no simulations involved.****
>>
>> ** **
>>
>> I’ve tested the separate steps but not yet the whole workflow. I may need
>> to extend the simulation by doing an hourly simulation to obtain useful
>> daylight illuminances, probably by creating genskyvec+rtcontrib-loop, like
>> in Axel Jacobs’ rtcontrib tutorial. That may get computationally intensive,
>> in which case I may resort to using EC2.****
>>
>> ** **
>>
>> A few questions:****
>>
>> ·         Any experiences with something similar? Ways to simplify
>> /improve my workflow? Which errors will I likely run into?****
>>
>> ·         obj2rad generates an interpolated .rad file using texfunc.cal
>> and something called 'M-nor'. This means I can't use my material as a
>> modifier for rcontrib. For now, I have exported my model as simple planes
>> so that the materials can be used as modifiers, but is there a better way?
>> ****
>>
>> ·         Should I use a CPU-optimised instance on EC2? What are some
>> ways to properly do parallel computing on EC2? Any examples?****
>>
>> ·         An alternative is using one material for the dome and creating
>> a custom binning for rtcontrib. Does this have any computational advantages?
>> ****
>>
>> ** **
>>
>> Any help greatly appreciated!****
>>
>> ** **
>>
>> Cheers,****
>>
>> *Reinier Zeldenrust
>> *Environmental Designer****
>>
>> Atelier Ten
>> Building Services Engineers + Environmental Design Consultants
>> CIBSE Building Services Consultancy of the Year 2011****
>>
>> [image: image001][image: image003]<http://www.amazon.co.uk/Green-House-Sustainable-Gardens-Singapore/dp/1935935569/ref=sr_1_2?ie=UTF8&qid=1351789637&sr=8-2>
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>>
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