Condensation and Moisture on Windows Glass Surfaces

Ouside temperature, inside air condition and condensation on inside glass windows

The combination of

  • outside temperature, and
  • inside air condition - inside dry bulb temperature 65 oF (18.3 oC) and variable inside relative humidity, and
  • moisture condensation on inside surfaces of glass windows

are indicated in the charts bellow.

Condensation glass surfaces

Windows - Overall Heat Transfer Coefficients U

  • Single glass window : U = 1.13 (Btu/ft2 oF hr) =  6 (W/m2 oC)
  • Double sealed glass window U = 0.58 (Btu/ft2 oF hr) =  3 (W/m2 oC)

Example - Condensation on Window Surface


  • an indoor relative humity of 50%, and
  • a window with a single glass with an U-value of aprox. 6 (W/m2 oC), 1.13 (Btu/ft2 oF hr)

- condensation on the inside of the glass will occur from outside air temperature 6oC (43oF) and below according the chart above. 

Related Topics

  • Heating - Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more

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