The quantity of heat that an element loses

The quantity of heat that an element loses is described by the following thermal transfer between two opaque elements:Conduction-Convection-Conduction. This can be described by the equation Q=A/R·ΔT=A·U·ΔT [W]. A is the area of the element [m²], R is the thermal resistance [m²K/W] and U is the thermal transmittance [W/m²K], while ΔT is the difference of temperature [K]. The temperature difference of the construction element compared to the interior air is of maximum 4 °C. Tsi=Ti-ΔT/R·Rsi (the temperature on the interior surface of a constructive element without forming a thermal bridge).