Source google image: https://upload.wikimedia.org/wikipedia/commons/8/84/Sch%C3%A9ma_mesure_conductivit%C3%A9_thermique.png
Isolation thermique formule
Source google image: https://upload.wikimedia.org/wikipedia/commons/8/84/Sch%C3%A9ma_mesure_conductivit%C3%A9_thermique.png