Short answer
Heated glass is warmed by an electrically resistive layer inside the laminated build-up. The current keeps the surface above the dew point, so fog does not form and ice and snow melt.
Two main methods
- Micro-wire heating: very thin wires embedded in the interlayer act as the heater. Evenly spaced wires spread the heat uniformly and are not noticeable at normal viewing distance.
- Transparent conductive coating: a thin, transparent, conductive coating on the glass works as the heater. Its resistance and light transmission are chosen together.
In both methods the current is fed through conductive strips called busbars along the edges, with the cable leaving at the edge.
Values set in the design
- Power density: power per area; lower for demisting, higher for de-icing.
- Supply voltage: chosen for the vehicle's or ship's electrical system.
- Heated zone: the whole pane or only the viewing area.
- Control: a temperature sensor and controller prevent overheating.
Where is it used?
Armoured vehicle windscreens and side windows, ship bridge and wheelhouse windows, machinery working in cold climates and yacht glazing. SOLAS V/22 requires a clear view through at least two bridge front windows regardless of weather; heated glass, wipers and clear view screens (CVS) are used together for this.
Standard for ship windows
ISO 3434 is the reference for heated glass panes in ships' rectangular windows.