One face is hot, the other is cold, and heat crosses the material in between at a rate set by Q/t = k · A · dT ÷ d. Drag the four sliders, or jump the conductivity between real materials, and watch the watts respond.
Heat-flow rate Q/t = kA·dT ÷ d
50.0 W
0.040 × 10.0 × 20 ÷ 0.160
Heat flux q (W/m²)
5.000
Resistance R (m²·K/W)
4.000
U-value (W/m²·K)
0.250
Energy per day (kWh)
1.200
Conductivity k0.040 W/m·K
Area A10.0 m²
Temperature gap dT20 K
Thickness d0.160 m
Material presets (k)
Steady state · conduction only · one-dimensional flow · no convection or radiation · k held constant with temperature.
Tip: thickness is the one slider with diminishing returns. Each equal step of d buys less than the one before, because the rate falls as 1 ÷ d rather than in a straight line.