How much heat leaks through a wall? Stack up layers like resistors in series and see where the insulation earns its keep.
Composite Wall Heat TransferLive
R-value & U-value
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Heat flows through a wall like current through resistors in series. Each layer's thermal resistance is its thickness over its conductivity; adding them gives the total R-value, and the heat flux is the temperature difference divided by it. Insulation, with very low conductivity, dominates the R-value — the steep temperature drop shows where it does its work.
Reading this result: The insulation layer carries the most thermal resistance, so the temperature falls most steeply across it. A total R-value of 2.71 m²K/W lets 9.6 W/m² flow for this 26°C difference.
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How it works
Steady heat conduction through a layered wall behaves like current through series resistors: each layer's thermal resistance is its thickness divided by its conductivity, and the total R-value sets the heat flux for a given temperature difference. Low-conductivity insulation dominates the R-value, producing the steep temperature drop you can see across it — the basis of building energy efficiency.
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The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.