Heat Conduction Calculator
Find the steady-state heat flow through a wall or slab using Fourier's law of conduction.
How it works
Q = k · A · ΔT ÷ d · (d = thickness)
Fourier's law says heat flows through a material in proportion to its conductivity k, its face area A, and the temperature difference across it, and inversely with its thickness d. A good insulator has a small k, so a thin layer of fibreglass slows heat far more than a thick slab of brick. The result is the steady-state power in watts crossing the material.
Worked example
A 10 m² fibreglass panel (k = 0.04 W/m·K), 0.1 m thick, with 20 K across it, conducts Q = 0.04 × 10 × 20 ÷ 0.1 = 80 W.
Sources: Thermal conduction — Wikipedia
Frequently asked questions
What is thermal conductivity?
It is a material property, k, in W/m·K, measuring how readily it conducts heat. Metals like copper (~400) conduct extremely well; insulators like fibreglass (~0.04) conduct poorly, which is exactly what makes them good insulation.
How does thickness affect heat loss?
Heat flow is inversely proportional to thickness: doubling the insulation thickness halves the conductive heat loss, all else equal.
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This calculator is for educational purposes. Double-check important results before acting on them.