BPI Certified: The Building Performance Institute (BPI) is the nation's leading building science accreditation organization. This organization teaches the "house as a system" philosophy - which looks at a building's various components (building envelope, attic, basement, combustion equipment, ventilation sources) and the interrelationship between them to maximize a home's performance. This approach leads to greater energy efficiency, but perhaps more importantly to buildings that simply work better. A home that has been analyzed and upgraded from a whole-house standpoint is more durable, healthier, more comfortable, and more energy efficient. For more information about BPI's standards, take a look at their Technical Standards for Building Analysts (PDF).
We recently employed Energy Reduction Specialist of North Carolina to assist us in upgrading and weatherizing a secondary home for energy conservation. This involved many modifications due to the home being 63 years old. The home needed to have a central heating and air unit installed in addition to many other upgrades and modifications. I previously just had a bad experience with another construction co. and had many reservations about starting another construction project. I was pleasantly surprised.