Home Insulation R-Value Savings Calculator
Estimate your annual heating and cooling cost savings when upgrading your home's insulation from a current R-value to a higher R-value.
Formulas Used
Annual BTU Reduction (heating or cooling):
ΔQ = Area (ft²) × Degree Days × 24 hr/day × (1/Rcurrent − 1/Rnew)
Heating Savings (gas): Savings = ΔQheat ÷ (η × 1,000,000) × Costgas
Heating Savings (electric): Savings = ΔQheat ÷ (COPheat × 3,412.14) × Costelec
Cooling COP: COPcool = SEER ÷ 3.412
Cooling Savings: Savings = ΔQcool ÷ (COPcool × 3,412.14) × Costelec
Simple Payback: Payback = Estimated Install Cost ÷ Total Annual Savings
Assumptions & References
- Heat transfer is modeled as steady-state conduction: Q = A × ΔT / R (ASHRAE Fundamentals).
- Degree days are multiplied by 24 to convert daily °F-days to hourly °F-hours.
- 1 kWh = 3,412.14 BTU; 1 MMBtu = 1,000,000 BTU.
- SEER is converted to COP by dividing by 3.412 (Wh/BTU × 1000 factor).
- Gas furnace efficiency entered as AFUE (e.g., 0.80 = 80%); heat pump as COP (e.g., 3.0).
- Rough installed insulation cost estimated at $1.50/ft² per R-10 added (DOE/EnergyStar typical range).
- Model assumes uniform insulation over the entire specified area with no thermal bridging.
- Heating and cooling degree days can be found via NOAA Climate Data Online or local utility.
- Reference: DOE Energy Saver – Insulation; ASHRAE 90.1 Standard; Oak Ridge National Laboratory Building Envelope Research.