Air spaces and windows
Air spaces Air conduction resistance R = 8/?i
Where R = air conduction resistance 8 = air layer thickness X = thermal conductivity ( 0.023 W/m K for air)
“Ideal case” for 0.02 m thick of air layer
R = 8fk = 0.02/0.023 = 0.87 m2 K/W
Because of convection and radiation effect, the actual R is between 0.1 to 0.7 m K/W.
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