In the slums of many third world countries, homes are constructed out of cement blocks with corregated sheet aluminum roofs. This prevents any natural light from getting in. See how they light their homes. You will be hard pressed to find a greener solution. On another topic, don't forget to stop by the RanDome booth in Maine at the Common Ground Country Fair September 23-25, 2011, where you can speak to RanDome inventor Richard Fischbeck about geodesic shelters and take part in fun educational activities.