Home Energy Rating System

HERS is an acronym which stands for ‘Home Energy Rating System’. The HERS system is a nationally recognized system which was developed by the mortgage industry. A HERS Index is simply a number from 0 to 100 that compares the overall energy usage of a home, the number determined by a simple yearly computer simulation of the home. The ‘As-Designed’ home, with the exact insulation, mechanical system, appliances, etc. is compared to an identical home if it were constructed with those features as specified in the 2006 International Energy Conservation Code. In effect, the HERS Index of the ‘As-Designed’ home is a percentage of the energy used for the same home if it were a typical new, code-built home. A score of 0 means that the home is a ‘Net-Zero Energy Home’, a home that produces as much energy as it consumes. On the other end of the spectrum, a score of 100 means that the home is a typical new home.


The HERS Index is a comprehensive comparison, as it accounts for insulation quantity and quality, air infiltration (as determined with a blower door), appliances, windows (quality, quantity, and shading), mechanical system, and duct leakage (as determined with a duct blaster). The HERS system is oftentimes referred to as a ‘Performance’ pathway for energy code compliance. There are many possible combinations for the above construction characteristics. The HERS ‘Performance’ pathway considers the combination of these in the yearly computer simulation and correspondingly computes a numerical HERS Index. A home could have an incredibly leaky envelope, poor insulation, and a highly efficient mechanical system. The same Index could be achieved with excellent windows and insulation and a poorly performing water heater or boiler.


Energy Innovations provides cost-effective HERS ratings. Boulder County and the City of Boulder have required HERS ratings for many years, and will continue to do so into the future. Many other building jurisdictions are considering adoption of the rating system as well. Other programs such as Energy Star and LEED require a HERS rating as part of their compliance. To read more about the nationwide HERS program: www.resnet.us