Daylight Problem

Forum for users to discuss the DesignBuilder Radiance daylighting tools and ask questions

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Posts: 7

Daylight Problem

Postby pmcmm » Fri Nov 16, 2012 10:49 am

Hello, I am trying to calculate daylight factor in a very peticular building shape. I want to model the daylight distribution in order to achieve a good overall distribution, and I have been playing around with the Visible Absorptance value.

What I could verify is that there is absolutely no difference in that value variation.

The map I show you is with 0% of absorption in inner material of wall, ground floor and flat roof, which should give me really nice daylight distribution, and as you can see they don\\\'t. I am testing and comparing the results with the Dialux software, and I start to wonder if the Daylighting Moudle is trustworthy.

Please give me some feedback about this question as soon as possible.
map.jpg (59.04 KiB) Viewed 46463 times
building.jpg (52.44 KiB) Viewed 46463 times
Andy Tindale
Posts: 2669
Location: Stroud

Postby Andy Tindale » Fri Nov 16, 2012 6:39 pm

You should see a difference in daylight illuminance results when changing the material visible absorptance for any material that is selected as the innermost layer in a construction in the zone. I would in particular expect to see noticable variations due to changes to ceiling/roof innermost material visible absorptance.

Do you see no change in results at all when you change surface absorptance? Or just minor changes?

Posts: 7

Postby pmcmm » Mon Nov 19, 2012 7:59 am

The problem is that I see really small difference between both analysis. I am attaching both maps that represent the problem. The first one has high reflectance materials (80% walls and ceiling, and floor 40%) and the second the reflectances are null.

I am aware that I must change the values in the innermost layers, and that the value of the material reflectance is 1-Visible absorptivity.

Anyway, I think the correct map would always have some light in halfway due to light reflectance. So, in my opinion, the problem is in the map number 1.

1-map no window.jpg
Map with high reflectance materials
1-map no window.jpg (56.55 KiB) Viewed 46441 times
Map with materials of 0% reflectance
2-map3noreflectance.jpg (58.38 KiB) Viewed 46441 times
Posts: 6
Location: Poland

Daylight Problem

Postby HerbeMannABg » Tue Oct 17, 2017 10:58 am

Can somebody tell me how to change the surface reflectivity of walls and floors for daylight analysis and also the scale of the map in daylighting? Thanks in advance
Luis Sousa
Posts: 370
Location: Stroud

Re: Daylight Problem

Postby Luis Sousa » Wed Oct 25, 2017 11:54 am

HerbeMannABg wrote:Hie,
Can somebody tell me how to change the surface reflectivity of walls and floors for daylight analysis and also the scale of the map in daylighting? Thanks in advance

- Surface reflectivity
You will need to change the material Surface properties of the innermost layer of your construction. ... erties.htm

- Scale map outputs
This can be done by applying the 'Apply scale "too dark" colour' or 'Apply scale "too bright" colour' options. See link below for more information: ... ptions.htm


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