The HERS (Home Energy Rating System) index scores a home’s energy efficiency relative to the RESNET reference home (built to 2006 IECC): HERS 100 = reference home (approximately 2006 IECC code minimum); HERS 0 = net zero energy home; HERS 50 = 50% more efficient than reference; HERS 61 = ENERGY STAR for Homes requirement for Zone 5. The HERS rating is calculated by a RESNET-certified rater using energy simulation software with actual as-built specifications — insulation R-values, window U-factors, blower door result, duct leakage, HVAC efficiencies, water heater efficiency. The HERS index is the common performance currency for residential energy certification: ENERGY STAR requires a specific HERS; DOE ZERH requires HERS ≤ 45; net zero requires HERS ≤ 0 when solar PV is included. RainFire Builders delivers the HERS certificate at project closeout for all ENERGY STAR and above projects.