Heat Conduction Calculator
Q/t = kAΔT/d, with the R-value.
Work out Heat Conduction. Q/t = kAΔT/d, with the R-value. Free, with no account and nothing to download.
Fibreglass 0.04, brick 0.7, glass 1.0, concrete 1.7, steel 50, copper 400.
Optional — gives total energy. 3600 is an hour, 86400 a day.
Rate of heat flow
80 W
R-value 2.5 m²·K/W · 8 W/m²
Q/t = kAΔT/d. Heat flow is inversely proportional to thickness, so doubling insulation halves the loss — but that is a reciprocal, not a straight line, and it is why the first inch does most of the work. Going from none to 50 mm saves far more than going from 200 mm to 250 mm. The range of conductivities is enormous: copper conducts ten thousand times better than fibreglass. Metals feel cold at room temperature not because they are colder but because they pull heat out of your hand that fast. R-value is thickness over conductivity, which is why it is the number quoted on insulation — it already combines the material with how much of it you are getting.
How the Heat Conduction Calculator works
Enter conductivity, area, temperature difference and thickness for the rate of heat flow, plus the R-value and the total energy over any period. Heat flow is inversely proportional to thickness, which is why the first inch of insulation does most of the work.
Also known as: thermal conductivity calculator · heat loss through a wall calculator · r value calculator · heat transfer rate calculator
Frequently asked questions
How do I calculate heat loss through a wall?
Q/t = kAΔT/d — conductivity times area times temperature difference, divided by thickness. The result is in watts.
Does doubling insulation halve heat loss?
Yes, but that is a reciprocal rather than a straight line. Going from no insulation to 50 mm saves far more than going from 200 mm to 250 mm, which is why there is a point of diminishing returns.
What is an R-value?
Thickness divided by conductivity. It combines the material with how much of it you have, which is why it is the figure quoted on insulation products rather than conductivity alone.
Why does metal feel colder than wood at the same temperature?
Because it conducts heat away from your hand hundreds of times faster. You are not sensing temperature, you are sensing the rate at which you are losing heat.
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