Should we have laws that require homeowners to insulate in order to save energy? How will homeowners benefit from improved insulation? Should homeowners insulate if the cost to themselves of doing so exceeds the benefit to themselves? How do others in the community benefit from the decision of some to insulate and thereby reduce their consuption of engery? Do these spillover beneftis justify a subsidy to encourage homeowners to insulate? who would lobby for such a subsidy?