Sign: U
Unit of measure: W/m²K
A value specific to a particular building structure. Shows the amount of heat being transferred over the unit surface of the structure over a unit of time in the event of a temperature difference per unit.
The thermal transmittance is a reciprocation of the thermal resistance.
U = 1 / (Rse + Σ (d / λ) + Rsi)
The thermal characteristics standard sets requirements for the U-value for each building structure.
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