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Daylight calculation

Posted: Wed Oct 30, 2019 11:34 am
by FiFly
Hello,

I have been doing some testing with DAILux which seems rather straight forward in it's use.

Now I am curious if the daylight calculations i have done for a simple test object are correct ? Mainly because the outcome differs a lot from the ones calculated by hand with several methods.

Do you have any kind of sample file to crosscheck ? Also a pdf with all necessary data will do.

Which standards are applied to the DIALux daylight calculations ? DIN 5034 ?

Tks

Re: Daylight calculation

Posted: Wed Oct 30, 2019 7:27 pm
by FiFly
To avoid misunderstandings.

With correct I mean offcourse "If I have created the project correctly without making mistakes that might influence calculations".

Tks

Re: Daylight calculation

Posted: Fri Nov 01, 2019 5:52 pm
by FiFly
ok, I found a simple sample to check if i am using DIALux correctly.
I think I need to disable maintenance however to arrive at the samples %.
But changing MF factor in DIALux does not change the outcome ?
Same goes for CIA. Changing interval of maintenance does not change outcome ?
Only changing polution category changes the outcome....
I am doing something wrong ?

Re: Daylight calculation

Posted: Mon Nov 04, 2019 3:01 pm
by kvkozierowski
Hello,

It is correct that only the pollution category (and the ambient condition) changes the results of the daylight calculation.
The other maintenance factors are for luminaires only, there is no sun maintenance interval ;)

Best Regards
Kolja

Re: Daylight calculation

Posted: Mon Nov 04, 2019 5:43 pm
by FiFly
Tks, that makes sense. Re-reading your post dated 2017 you said exactly the same, but somehow I understood it differently.

But..this means I stay at least 20% under the outcome of the simple example project.

Any idea why daylight factors remain so low....what can be done wrong ?

Re: Daylight calculation

Posted: Tue Nov 05, 2019 6:29 am
by kvkozierowski
Hello,

This seems plausible, the maximum light loss factor is 0.9 in evo and the standard glass trasmission factor is also 0.9. => 81% of the daylight you expect without pollution and glass transmission loss.

The standard light loss factor with pollution category "medium" and "clean" or "very clean" ambient condition is 0.8
With "low" and "clean"/"very clean" you can get to 0.9 but that is the maximum in evo.

The standard window glass transmission factor in evo is 0.9 (90%). You can change this to 100% (material tool).

Best Regards
Kolja

Re: Daylight calculation

Posted: Tue Nov 05, 2019 5:18 pm
by FiFly
Hello Kolja,

the curiosity regards the fact that all kinds of standards indicate various medium daylight factors. For example, residential projects mostly require 2% medium DF.

But if you design some typical rooms of 14 sqm (different shapes) with a glassdoor (1.0 x h 2.1) in the center, 30 cm walls / floor / ceiling, typical finishings and a small balcony (1.5 mtl. overhang) on a 50 x 50 mt base you have to enlarge that glassdoor significantly to obtain that average ? If you put a 3 storey building in front at 12 mt. you will never obtain that average ?

So either the 2% average is too heigh or something else is going on (DFmean instead of DFmedium ?) ??

That's why I thought a verified sample project would be helpfull.

To try to rebuilt it in DIALux and obtain the same results ?

At least one is sure the building & calculation part is correct.

Regards

Re: Daylight calculation

Posted: Tue Nov 12, 2019 6:08 pm
by FiFly
Hello, no more feedback on this ?

Re: Daylight calculation

Posted: Wed Nov 13, 2019 9:03 am
by kvkozierowski
Sorry, I do not think I am the right person to discuss the standards. I am a developer, not a lighting expert.
We have run several tests according to CIE171:2006 and in these test cases we did not found any significant errors. You can find these test cases online and recreate them in evo if you want to verify the results.
The standard daylight factor effective area in evo is just informative, you can also add a customizable daylight factor grid to your project and use this instead.

My personal opinion concerning most lighting design standards:
These standards are in most cases designed to fit very artificial cases and not the reality. They consider a standard rectangular room, an endless straight road etc. In most cases it is a very long text describing what to do and what not to do and in many cases this description is not unambiguous (should, may, can, ...) and needs interpretation. Some standards even contain errors and sometimes the people involved in the standard tell you not to calculate according to the standard because it makes no sense. These standards are not perfect and they might not be applicable to a specific case.

Best Regards
Kolja

Re: Daylight calculation

Posted: Thu Nov 14, 2019 8:27 am
by FiFly
That is what I am also afraid off.

But in case the standards are cited in the appliable building laws it becomes kind of a problem.

Tks for your replies......