Calibrating the sky illuminance

old forum
1

hello all,

Is there anyway to calibrate the sky illuminance from epw file with the correct measurement that I have? how can I do it?

-masoumeh

2

Masoumehta,

If you have both “Direct Normal Illuminance” and “Diffuse Horizontal Illuminance” measurements, you can create a high-accuracy calibrated sky by using the “Honeybee_Generate Custom Sky” component.

If you only have a Global Horizontal Illuminance value, you can create a uniform sky by using the “Honeybee_Generate Sky With Certain Illuminance level” component. However, this is going to be very inaccurate unless the values that you have recorded are for an overcast cloudy day.

-Chris

3

thank you very much chris, I’ll try this.

-masoumeh

4

Chris said it all. Just a warning that if you’re creating the sky for a non-cloudy day then using the second method is not recommended. You can use watch the sky component to check the illuminance value under the generated sky. A good place to start is probably the weather data around the time that you have done the measurement:

If you have an HDR image of the sky there are more advanced solutions that you can find on the web.

customWeatherFile.gh (433 KB)

5

thanks alot mostafa!