Convert Wh/m2 to lux

Hi everyone
Is it possible a radiation convert from Wh/m2 to lux for the total radiation of a room?

Hi Raphael,

Although lux (lumen/m2) is a unit of measuring for luminous flux, it is very difficult to convert solar radiation (Wh/m2) to lux. When we use lux, we are measuring the amount of visible light, or solar radiation within 400-700 nm (roughly) and there are different conversion factors for every wavelength. Also, the amount of luminous flux within this range in the indoor environment is dependent on your glazing’s SHGC and other material properties. Imagine how difficult this gets once you account for reflected light/radiation off of interior materials.

I’ll try to find some reference to help explain this more thoroughly. I hope this helps in the meantime.

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I believe this question is related to this one. To have a design that does not annoy the users is qualitative. I would recommend you to narrow down on performance metric / metrics that you can track and optimize. The next step would be to find any industry recognised reference that mention acceptable ranges for those performance metrics. For example, if you are designing a classroom, one of the performance metric would be Useful Daylight Autonomy. And for reference, you may check the IESNA Handbook.

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As a rule of thumb I would use 85lm/W for sunlight and 120lm/W for diffuse skylight but that is only valid-ish for direct daylight outdoor (you may want to research on luminous efficacy of daylight to find out more on the topic).
As soon as it passes through or bounces off materials, this no longer applies as @KitElsworth mentioned.

Maybe new tools like Solemma’s Alfa would be able to do what you are after ?
I am not familiar with spectral raytracing but would love to hear more about it.

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