Comparing Ladybug tools results to IDA-ICE results


I recently compared the Daylight Factor results of an IDA-ICE daylight simulation with the results of a Ladybug Tools simulation and got very different results particularly in relation to the minimum Daylight Factor in the rooms, with the Ladybug Tools simulation showing much higher minimum Daylight Factor values (almost 200% higher in some cases).
Has anyone looked into this as well? Or can advance what the reasons for these differences might be?
IDA-ICE also uses Radiance as the simulation engine therefore I was expecting the values to match much better. Radiance rendering parameters are the same in both programmes. There are some differences regarding the grid resolutions between the models (could not make these match 100%), but I find it difficult to think that could be the reason for the big differences I get for the minimum.

Best regards

Hi @Raquel, have you checked the following?

  • Same (if any) allowance for reduction in daylight due to frame
  • Reflectance values of the surfaces
  • Light transmittance of the glazing
  • If wall thickness has been accounted for
  • Wall offset is comparable between the two
  • Does IDA ICE include any dirt factors by default for glazing

You could also check the Radiance scene generated by each using the Spider viewer

1 Like

I’d check local code requirements before factoring these in.

I’d encourage @Raquel to upload her files. Probably can be debugged and finding small differences such as grid height etc.

Usually I’d say if radiance parameters are somewhat correct, then usually in Rhino you have more precise geometry and slightly more conservative values since IDA ICE usually have quite bad window frames and wrong ceiling heights if that comes from BIM.