I am trying to model a building that is using titanium shaders over the windows. The issue is whether the radiation reflected by the shader on its top surface will increase the solar radiation passing through the window on the floor above, and cause additional heating. There may also be secondary reflections on the underside of this shader too.

I've model this in Ecotect and using solar rays i have found that there is indeed going to be an issue of reflected radiation. The problem arises when I decided to test for different materials... Changing the various values for specularity, solar absorbtion, emissivity etc made no difference to the incident radiation. I'm using an analysis grid behind the full height window and the shaders are also set to solar reflectors but I can't seem to make it work. I even simplified the model to show just the shaders and only one reflection but it still don't seem correct.

Thanks