Does Putting Reflectix in Your RV Windows Cause the Windows to Crack?

It didn’t take very many months of living in our RV to figure out we needed better insulation. We don’t spend much time in cold areas, but the hot places sure can get hot, and the lack of insulation means the RV heats up like an oven.

One of the best solutions we’ve found? Reflectix in the windows.

Reflectix has done a wonderful job of helping keep us cool in the summer and has even helped keep our rig warm on the rare occasion that we’re somewhere cold. That said, I have seen a lot of debates recently about whether putting Reflectix in your RV windows is a good idea. Many seem to think the stuff could actually make your RV windows crack.

In this article, I will explore this idea in order to help you decide whether you should put Reflectix in your RV windows or not.

What is Reflectix and Why Use It?

Before we go any further, let’s take a moment to talk about what Reflectix actually is. Essentially, this stuff is bubble wrap sandwiched between layers of reflective aluminum foil. It’s sold in rolls at hardware stores, often marketed for home use—attics, crawl spaces, ductwork, etc. It can be cut to fit into RV windows and offers many benefits.

These include:

• Temperature control: In hot climates, it reflects sunlight and reduces interior temperatures dramatically. In cold climates, it adds insulation by reducing radiant heat loss.
• Privacy: When fitted inside windows, it blocks outside visibility completely.
• Light control: Perfect for boondockers or light-sensitive sleepers who want pitch-dark interiors.
• Energy savings: Reduces the workload on your air conditioner or heater.
• Cost and convenience: Easy to cut, lightweight, and inexpensive compared to custom window coverings.

The Cracking Concern

Obviously, this is pretty great stuff we’re talking about. So what’s the upset about? Well, the fear comes down to heat buildup.

Here’s the idea: When you put Reflectix against a window, sunlight hits the glass. Instead of passing through or dissipating naturally, the sunlight bounces back and forth between the Reflectix and the glass. This can trap intense heat in that thin gap, causing the glass to heat unevenly, expand at different rates, and eventually crack.

Is There Evidence of Reflectix Causing Cracks?

If you think about it, it’s a logical worry. After all, glass does break under stress, and windows are some of the most fragile components of any RV. That said, I’ve never met another RVer who has had windows crack due to Reflectix, and we certainly haven’t had this problem ourselves.

I wanted to find out if this was a real world problem, so I did some digging. Here’s what I found.

Anecdotal Reports

You’ll find RVers online who claim their window cracked after they used Reflectix. Often, they’ll describe the window cracking on a hot day with Reflectix pressed tightly against it.

Manufacturer Warnings

Some RV and window manufacturers do caution against putting reflective materials directly against double-pane glass. They don’t always mention Reflectix by name, but the warning is essentially the same: Trapped heat can cause problems.

Home Application Parallels

In residential settings, glass experts often recommend leaving an air gap when installing reflective window films or coverings for this exact reason.

So no, there’s no scientific study showing a direct cause-and-effect relationship. However, the risk may not be entirely imaginary. Still, it is important to keep in mind that it’s totally possible that Reflectix isn’t the real culprit in any of the anecdotal cases mentioned above. Windows can crack for other reasons, including manufacturing defects, road vibrations, pre-existing chips, or natural thermal expansion unrelated to Reflectix.

Types of RV Windows

It is important to note that the risk of windows cracking due to Reflectix changes based on the type of RV windows you have. Let’s take a look at the different types of windows and whether they might be negatively affected by Reflectix.

Single-Pane Windows

Single-pane windows are most common in budget and older RVs, and they are what we’ve always had. They use just one sheet of tempered or laminated glass. They are less insulated and more prone to condensation, but are less likely to trap excessive heat from Reflectix since there’s no sealed air layer. This might explain why we’ve never had an issue with Reflectix.

Double-Pane Windows

Double-pane windows are found in many modern or high-end RVs. They use two layers of glass with an insulating air (or gas) gap between, making them excellent for temperature control and soundproofing. That said, they are more vulnerable to stress cracks if heated unevenly since the sealed cavity can amplify temperature differences. Fortunately, Reflectix is less necessary when you have these well-insulated windows.

Acrylic or Polycarbonate Windows

These are much less common windows, only found in some lightweight RVs and specialty rigs. They are very resistant to shattering but can warp or craze under extreme heat.

How to Use Reflectix Safely

As you can see, the cracking concern is mainly directed at double-pane windows, which are more sensitive to thermal stress. If you don’t have double-pane windows, you’ll probably be just fine using Reflectix—and even if you do, you can likely use the stuff safely with the tips below.

Leave an Air Gap

The most important thing to do? Don’t press Reflectix flush against your window. You can use Velcro strips, Command hooks, or a homemade frame to hold it slightly away from the glass. Even a half-inch gap allows heat to spread safely.

Avoid Direct Sun on Double-Pane Windows

If you have dual-pane glass, be extra cautious. You might consider using Reflectix only in windows that don’t get full afternoon sun exposure, as this intense sunlight is what is most likely going to cause damage.

Consider Alternatives

Reflectix is great, but it’s not the only option. You might consider using one of the options below if you’re worried about cracking.

• Blackout curtains or thermal drapes: These insulate without trapping heat directly against the glass.
• Window tint films: Professionally applied films can cut heat and UV rays without risk.
• Magnetic or fabric window covers: Lighter and less heat-trapping than Reflectix, especially when put on the outsides of windows.

Myths and Misunderstandings

Like many RV debates, the Reflectix window-cracking question comes with myths on both sides. Let’s clear a few up so you can rest easy knowing you’ve made the right choice for you and your RV.

Reflectix Always Causes Cracks

This is definitely false. In fact, the majority of RVers use it without ever experiencing a crack.

Cracks Never Have Anything to do With Reflectix

This one is also false. While rare, trapped heat can indeed stress glass, especially in double-pane windows, so you do want to make sure you are using Reflectix properly in order to avoid issues.

Reflectix Provides Insulation by Itself

This is misleading and something I myself believed until I dove into this research. In reality, Reflectix mainly reflects radiant heat. Without an air gap, its insulating (R-value) effect is minimal. This makes that air gap even more important!

Using Reflectix Voids All Warranties

Not universally true, but some window manufacturers may refuse coverage if reflective barriers are used incorrectly, so make sure you take the right steps to keep cracking from happening.

So… Will Reflectix Crack Your RV Windows?

So will Reflectix cause problems for you? Honestly, probably not. If you have single-pane windows, the risk is incredibly low, and even if you have double-pane windows, you aren’t likely to see problems unless you install the Reflectix without an air gap.

In other words, the problem isn’t Reflectix itself—it’s how you use it. We will continue to use it in our rig, but will be more mindful about leaving an air gap to prevent cracking and make sure we are getting the best possible insulation.