Can I double up window film? 2 Things You Need to Know

Can I double up window film on my window? This is a question I just got asked again the other day. Ordinarily, I try to steer them towards our darkest film option: ComforTech 05 – which has just a 7% visible light transmission and a TSER of 82% – but some folks still want to see if they can improve on that by doubling up.

Since we run into the question of whether you can double up window film every once in a while, so I thought we’d tackle it in today’s post.

Will doubling up the film “work”

This is the question we get asked the most and there are two parts to it (1) are you physically able to mount one piece of film on top of another, and (2) how well will doubling up the film work in terms of performance specifications.

Let’s take them one at a time:

Can You Double Up Window Film

The simple answer to this is yes. It is possible to add a second layer of film of our film to one that is already on the glass.

But, you won’t be able to put them on top of each other at the same time. Our ComforTech™ Ceramic Series window film has a dry adhesive that makes the film easy to apply. But it also needs a longer curing time.

That means to double up a film with a dry adhesive (read more about adhesives here) you would need to apply the first film and then let it cure for at a minimum of 30 days before attempting to apply a second dry adhesive film.

If you are applying a pressure-sensitive adhesive film over another pressure-sensitive adhesive film, we would still recommend allowing the first film to cure for at least two weeks before attempting to film over it.

Performance Specifications

The second part of the question is how will doubling up improve the performance of the film.

If you read this blog on the regular, you know we talk about window film as a high-tech product. It’s not just a piece of plastic you throw on your glass. It actually is designed to change the properties of the glass to reject and/or absorb some of the sun’s energy across the electromagnetic spectrum. (Find out more about how window film works here.)

And all professional-grade window films are rated by the National Fenestration Rating Council or NFRC. They rate window performance primarily but also rate window film.

Our film (which is made for us under a confidential white label agreement by one of the largest global window film manufacturers) is rated by the NFRC and given performance specifications. You can see our ComforTech performance specifications here:

The film is only rated as a single layer on glass. So many will ask us what the performance will be if the film is doubled up. And while we can say it will improve, we haven’t tested what the performance will be if you double up the film.

Double Up Window Film Summary

You can double up window film if you are trying to maximize the solar control or privacy of the film. It’s not something we necessarily recommend doing, because we haven’t rated the film for doubling, but it can be done and customers have done it in the past.

The main things to consider if you want to double up window film are: (1) you need to allow the first layer of film to cure before you apply the second layer, and (2) we don’t test for two layers of film so we make no claims or warranty about the performance of the film.