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Insulation Savings Calculator
Quick answer: This rough model estimates heat lost through the ceiling before and after an upgrade using area, R-values and your heating degree days, then converts the difference into fuel and dollars using your fuel price and system efficiency. It ignores air leaks, framing and cooling, so read the result as a ballpark, not a promise of savings.
How it works
Heat loss (BTU/yr) ≈ area × 24 × HDD ÷ R. Savings = loss at old R − loss at new R. Fuel units = BTU saved ÷ BTU per unit ÷ efficiency. Dollars = units × your price. Heating degree days for your area come from weather services or your utility. The model treats R as the whole-ceiling value, which overstates savings when the old R is very low and air leakage dominates. For official guidance on savings and priorities, see ENERGY STAR and Natural Resources Canada. A professional energy assessment gives better numbers.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: 1,000 sq ft ceiling, R11 to R49, 6,000 HDD, natural gas at a made-up $1.20 per therm, 90% furnace. Heat saved ≈ 10.2 million BTU. Fuel ≈ 113 therms. Savings ≈ $135 per year.
FAQ
Why are my bills not dropping that much?
Air leaks, ducts and behaviour matter; see air sealing first.
Does it include cooling?
No.
Where do I find HDD?
Weather services and many utilities publish them.
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