Just a couple years back, anyone who said they could build a $180,000, 1,600 square-foot house that featured foam insulation inside a high-performance wall system, high-efficiency solar-powered HVAC and water heating , a weather sensing irrigation and water management system, and home-control software to manage it all could only have been either an inmate or a member of Congress (nuts or a liar, or both). Just the systems involved would have accounted for nearly half the cost, leaving about $60 per square foot for construction, minus a very small profit. Meritage Homes (NYSE:MTH), Scottsdale, Az., has done just that at