On Outside of Windows
On Inside of Windows
On the Frame & Sash
On Energy Efficient Windows
On Wood Windows
On Vinyl Windows
On Aluminum Windows
Frost on Windows
Condensation Problems
Window Glass Temperature
Frequently Asked Questions


Frost on Windows
  Window frost (also called fern frost) forms when a glass pane is exposed to very cold air on the outside and moderately moist air on the inside. If the pane is not a good insulator (such as a single pane window), water vapour condenses on the glass forming patterns.

With very cold temperatures outside frost can appear on the bottom of the window even with double pane energy efficient windows, due to air convection between two panes of glass. Bottom part of the glazing unit is always much more colder then top part. The glass surface influences the shape of crystals, so imperfections, scratches or dust can modify the way ice nucleates. If the indoor air is very humid, rather than moderately so, water would first condense in small droplets and then freeze into clear ice.


|On Outside of Windows| |On Inside of Windows| |On the Frame & Sash| |On Energy Efficient Windows| |On Wood Windows| |On Vinyl Windows| |On Aluminum Windows| |Frost on Windows| |Condensation Problems| |Window Glass Temperature| |Frequently Asked Questions|