This could be answered in many ways. What comes immediately to mind when you ask for a working model is to exhibit how a house could be weatherproofed using insulation and caulking, easily demonstrated in a model. Another model would be one showing the placement of landscaping trees and plants to shade the south side of housing in the summer and to create a wind barrier on the north side in winter. Another model could illustrate the use of passive solar energy (as on a roof) to heat water. Another would be to illustrate active solar energy (using solar panels to generate electricity) or geothermal heating.