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

[Germán Molina Larrain]

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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> F +44 (0)20 7729 5388****
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