ECOTECT and daylight calcs for LEED?

Xavier, You cannot use ECOTECT daylight reports for credit compliance. The reason is that ECOTECT does not have capability to do daylight calculation under "clear-sky" condition as it is required by IEQ c8.1. ECOTECT daylight calculation has only "uniform" and "overcast" sky condition options. However, you can export and do the calculation with RADIANCE engine by using ECOTECT.

what i heard was since "uniform" and "overcast" are both conditions where less light is generated than "clear sky" that technically using Ecotect provided a more stringent baseline environment and as such was admissible. Not sure why having less light to work with to meet the requirements would prevent you from using Ecotect?

The reason you are required to run simulations under clear skies is to evaluate glare conditions and direct solar issues. It is not about quantity but quality and this is a means by which these issues can be evaluated based upon current simulation limits.

Norma, If you would like to know the detail of each sky model, you can see the difference among their zenith/sky luminance value in each angle position. The Skymodel is usually chosen based on its relationship with real condition. In addition, there is a limitation in ecotect that it uses simplied split flux method and its skymodel model is not based on weather file. In my opinion, you may use overcast sky, if you have supporting document that the skies at your building location are mostly overcast skies. Otherwise I will agree with Todd that the clear sky is more appropriate in most US locations since it has direct sunlight component. Regarding evaluation glare issue, the simulation required by LEED is only for illuminance level. In order to study glare issue properly, luminance study will be required. The result of illuminance study cannot be used to determine potential glare issue. Hope it helps ..