Wall, Ceiling & Floor Heat Loss Calculator

Heat flows through an assembly in proportion to area and ΔT, and inversely to R-value.

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Formula

Q = A × ΔT ÷ R

Example calculation

400 ft² of R-20 wall at 70 °F ΔT → 1,400 BTU/h.

Practical HVAC use

Compare insulation upgrades and estimate component losses.

Common mistakes

Using nominal cavity R-value instead of effective assembly R-value.

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Educational tool. Results are estimates from the stated formulas; always confirm with manufacturer data and the code adopted in your jurisdiction. All calculators