They're made-to-measure clear plastic panes which pop just inside the frame of your existing windows.
By trapping a layer of air, which is a good insulator, they cut heat loss and emissions by half, which is nearly as good as conventional double glazing but at a fraction of the cost and hassle.
In this picture, taken with a thermal camera, only the left hand pane has a Gecko Pane installed. The orange colouring shows that it is warmer than the purple, blue and black right hand pane.
By keeping your windows warmer, they largely eliminate condensation:
Unlike any other system they fit almost any window, in seconds, with no tools or DIY skill needed. As they don’t damage windows in any way, and are fully removable, they’re particularly good for period properties.
A Gecko pane simply traps a 13mm layer of air beside the single glazed pane. This acts as an insulating layer, cutting heat loss by 50%.
The rate of heat loss of a surface is measured using "U-values." The impact of Gecko Panes can be verified using Pilkington's free U-value calculator (here, registration required), or try this simpler one.
These show that a single glazed pane has a U-value of 5.8 w/m2˚C, and that a double glazed pane with a 13mm air filled cavity (equivalent to having a Gecko Pane installed) has a U-value of 2.9 w/m2˚C, which is half as much.
The calculators also show that the thickness of the second sheet of 'glass' (plastic in the case of Gecko Panes) makes almost no difference to the U-value. Hence Gecko Panes achieve a 50% heat reduction using just 1mm thick clear plastic.
Gecko Panes drastically reduce condensation because they raise the temperature of the pane such that the dew point is less often reached. Noise transmission is also reduced.
Gecko Panes cost about £50 per square metre. Gecko Panes for average sash window panes cost about £15-20. Panes rarely cost more than £40. An average four pane sash window therefore costs about £75-£100 to "Gecko glaze". A six pane bay window tends to cost about £100-£150. Installing Gecko Panes for an entire home will rarely cost more than a few hundred pounds altogether.
That depends upon a range of factors, including your type of heating system (gas, electric etc.) and its efficiency, how much you pay for gas or electricity, and the temperature to which, and how often, you heat rooms in which you install Gecko Panes.
However, as a general rule of thumb, in addition to the immediate comfort, emissions and condensation benefits of Gecko Panes, they should pay for themselves in 2-6 years in fairly normal circumstances.
What we can say fairly confidently is that Gecko Panes will tend to pay for themselves around ten times faster than conventional double or secondary glazing.
The differences, from a performance point of view, between conventional double glazing and Gecko Panes is that double glazing also uses "low-emissivity" glass and inert gas in the cavity to cut heat loss further.
In standard double glazing these measures improve the U-value to about 1.8-2.0 W/m²°C from 2.9 W/m²°C, but this is an improvement of only about 15-20 percentage points. In other words, 80% of the benefit is achieved simply from trapping a layer of air, which is what Gecko Panes do.
The following infrared pictures show the impact of installing a Gecko Pane. In this picture, only the bottom left pane has a Gecko Pane installed. Note the dark blue of the other panes, indicating that they are colder:
In this pic, all panes other than the bottom left have Gecko Panes. Again, note the dark blue of the single glazed pane:
Physics mean that Gecko Panes will deliver their promised heat loss reduction, but it's nice to have tangible evidence of their performance. On very cold days, the difference made by a Gecko Pane is clear, especially if you have a single glazed pane next to it. Placing your hand near to the surface of each, you'll notice that the one with the Gecko Pane feels several degrees warmer. Rooms with Gecko Panes should feel noticeably warmer than previously.
Another indication of performance is that Gecko Panes significantly reduce, or even eliminate, condensation on panes that are otherwise prone to it. In the picture below, the left hand window has no Gecko Panes, but the right hand one does.
Finally, all other things being equal, fully outfitting a home with Gecko Panes should make a noticeable difference to your energy bills.
Gecko panes will prevent the inside glass surface of your window pane from becoming dirty. To clean the Gecko Pane itself, it's best to use a micro fibre cloth, if you have one, and a soap and water solution. Avoid using glass cleaning products which contain ammonia, as these may damage the pane.
Single glazing is a terrible insulator, transmitting 5.8 watts of heat per square metre per degree Celsius. That's five to ten times as much as a wall tends to, which is why single glazed windows feel so cold, and why they can be such a significant source of home heat loss.
As cold single glazed panes cool the air next to them the air sinks, drawing warm air down from ceiling height, causing convection currents (draughts) and discomfort and raising heat loss.
When the glass temperature is below the “dew point”, the warm air convecting past the window condenses water onto the pane causing misting and damp.
If your home has several single glazed windows, it will raise your heating costs, and the emissions associated with heating your home, significantly.