You can do it on the back of an envelope. Radius of curvature sets the focal length and the min and max elevations of the sun are set by your latitude. If there

You can do it on the back of an envelope. Radius of curvature sets the focal length and the min and max elevations of the sun are set by your latitude. If there's any elevation between the min and max where the reflection will hit the ground even close to the focal length of the building, you will have a problem. It's the same optics calculations anyone designing a concentrating solar power system would do, and while you need to be careful if you want accurate answers, it's not complicated to see if it has the slightest chance of working.