Our company builds energy-efficient custom homes. To do it right, we've invested a lot of money in training our workers and providing them with the proper diagnostic equipment. On the last house we completed, though - a modular - we didn't do a blower-door test until our clients had already moved in. That's because most of the air-sealing and insulation details had been taken care of before the house left the factory.Normally, a 4,150-square-foot house (including the basement) with an attached garage would take us about six to eight months to complete, depending on the finish details. Building with prefabricated...