ECOTECT, Design Sky Illuminance

[tinashu007]

Ecotect daylight calculation requires Design Sky Illuminance in lux. Ecotect offers two different calculation methods: Calculated from model latitude and Calculated from Tregenza Formula. Which one do you normally choose?

There are quite a lot information on the web about Tregenza Formula, but I have no idea about how Ecotect calculate Design Sky Illuminance from model latitude, can not find anything about this method. Could any one help me?

[Mike Sealander]

I believe the design sky from latitude is the same as IES design sky, meaning it simply places the sun in the sky where it would be at a particular latitude, regardless of the longitude or other factors. Design sky in general is a cool concept, as it models daylight based on how daylight behaves on a perfectly cloudy day. Not sure what the Tregenza is, but I use design sky based on latitude.