The Building Performance Institute (BPI) is the nation's leading building science accreditation organization. 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).
RESNET (short for the Residential Energy Services Network), is the premier accreditation organization for home energy raters and home energy auditors in the country. With an emphasis on new construction, RESNET certified HERS Raters (HERS is short for Home Energy Rating System) to analyze each element of home that may contribute to energy waste or energy inefficiencies. During a HERS Rating, we analyze each of these components, as well as their relationship to one another, to assign the home a score from 1-100 on the HERS Index. (100 is bad, 0 is good.) HERS Ratings are a mandatory part of the certification process for many green building certifications including Energy Star and LEED.