Window insulation film

Typical absorption for a silvered film is 65% for visible and infra red with 99% for UV.

A US standard (NFRC) uses a 39 °C difference which yields a smaller optimal gap width of about 13 mm.

One commonly used film is a heat-shrink plastic which is attached to the window frame using double-sided pressure-sensitive tape.

Reduced heat flow also helps prevent condensation[3][4][5] which is triggered when the temperature of the inside surface falls below the dew point.

Convection control film is often used in winter when the outgoing heat flow is more important, especially for single-glazed windows where the temperature difference is often sufficient to cause condensation.