Last updated on March 10th, 2024 at 03:42 pm

There’s a newer product now that advertises great savings on your energy bills while being nearly invisible (if you want it to be). It is replaceable easy installation window film.

The concept is simple and straightforward. Placing a special film, which can be cut or trimmed to size, over the window pane in theory reduces the solar radiation allowed in through the window and improves the R-value (insulation value) of the glass pane itself.

But does this really work? And does it save you money?

First, the solar radiation. The ideal way to test this is to gauge the temperature difference of a room with no film installed, then the same room with the film installed.

Turns out the film does prevent a moderate amount of heating. In a test a thermometer was placed in a shady area in close proximity of the window on a sunny day. Then the test was repeated with the film installed. The temperature remained relatively constant with the film, while the temperature rose slightly without the film.

Next, the insulating qualities. Remember that insulation only slows the transfer of heat. To test this, an IR temperature was taken of the window pane from the outside with and without the film installed. The temperature was lower from the outside when the film was installed, indicating that indeed the film had added insulation to the window.

On average, you can expect to pay $30 per window, depending on the size.

So, is worth it? And should you buy it?  Well, first of all, if you have newer windows (especially the ones that have an inert gas in the pane) chances are they are already UV coated. Therefore, the solar radiation is already cut down. And if the windows are newer, then chances are adding film will do little to cut down on your bills.

There’s another issue to consider as well. The film will work well if your high energy bills are a direct result of poorly insulated window panes. But if you have poor insulation in your walls or other energy gaffes, placing film over a window has the same effect as placing a stone in a stream and expecting the performance of a dam. It doesn’t make sense to repair something that isn’t going to solve the problem.

This just highligts the need to understand your home’s energy usage before you engage in repairs that can cost you hundreds of dollars.

that said, the insulative film does do a relatively good job of insulating poor windows…but at a cost. The film costs upwards of $20-$30 per sheet, and considering most homes have more than just one window, this can add up. Still they may be worth the money if you have poor window panes and you can’t afford to replace the whole window.

Otherwise, you might just be wasting money. Products like these are appealing because they promise a lot and appear to be doing something. But they can give the illusion of doing something – which in effect just takes money from you.