The unit of overall coefficient of heat transfer is

Kilocalorie per hour per square meter per degree Celsius (kcal/m² hr °С) is a metric unit of the heat transfer coefficient. The heat transfer coefficient has SI units in watts per squared meter kelvin: $$\frac{{\text{W}}}{{{{\text{m}}^2}{\text{K}}}}$$ . Heat transfer coefficient is the inverse of thermal insulance.