What is the Home Energy Index (HEX)?

The HEX is an indicator of a home’s energy performance. It is derived from monitoring the temperature at certain points over a period of time under controlled conditions. The HEX considers contributors such as the quality and performance of insulation and the performance of the heating system. The outside temperature or the effect of sunshine are largely eliminated from the results. The measurements must be taken on a cloudy or overcast day, with no other source of heat in use (such as a fireplace) than the main furnace. Results must include the type of system (forced hot air vs. hot water), and the sensors should be place at:

  • outside away from direct sunlight, at least 2 feet away from an exterior wall
  • inside at least 5 feet away from a direct source of heat, such as a radiator or heat duct
  • directly on a source of heat, e.g. a radiator, or at least 2 inches inside a heat duct

Program the thermostat for two 24-hour periods as follows:

  • 5:00am – 71°F
  • 7:30am – 65°F
  • 3:30pm – 71°F
  • 21:30pm  – 65°F