Does Window Film Reduce Heat? TSER and IR Explained

The short answer

Yes — window film rejects a real, measurable share of the solar energy that hits your glass. Across the range we install, total solar energy rejected runs from 45% to 84%, and infra-red rejection from 62% to 93%. Every one of those figures is measured on 1/4" clear glass; performance differs on dual-pane and Low-E glass.

That matters in a valley with more than 300 sunny days a year and summer highs well past 100°F. Rejecting solar heat before it crosses the glass may reduce cooling demand through the months your air conditioner works hardest. What it will not do is turn a west-facing great room into a north-facing one, and anyone promising you a specific temperature drop or a payback period is guessing at your house.

TSER and IR, in plain terms

Two numbers get quoted constantly and they are not interchangeable. Knowing the difference is most of what you need to shop sensibly.

TSER — Total Solar Energy Rejected

The share of the sun's total energy the glass-and-film system turns away: visible light, infra-red and ultra-violet added together. This is the honest headline number for heat. When you compare two films, compare their TSER.

IR — Infra-red rejection

Infra-red is the part of sunlight you feel as radiant warmth, and it is only one slice of the spectrum. This is why a film can advertise 90%-plus IR rejection while rejecting far less of the total. It is not a false number, it is just a narrower one, and it flatters a film in a way TSER does not.

What our films actually do

These are real figures from the specification sheet for the films we carry, not estimates. Five of the range, chosen to show the spread from near-clear to very dark:

Source: UCA Distributing window film specifications, 1 Jan 2023. All figures measured on 1/4" clear glass; performance differs on dual-pane and Low-E glass.

Read across the rows and the trade-off is obvious: the films that reject the most heat also let the least daylight through. Inviso 70 keeps nearly all your light and still takes out a useful share of the heat. Reflect Silver 15 takes out far more heat and changes how the building looks. Most homes land somewhere in the middle, and the right answer depends on which rooms are the problem.

Why your glass changes the result

Every figure above is measured on quarter-inch clear glass. That is the industry's standard test pane, and it is not what most St. George homes have. Newer builds here are typically dual-pane, and many already carry a Low-E coating that is doing some of this work before film is involved.

On those windows the film still helps, but the numbers shift, and the honest answer is that we tell you what we are putting on your specific glass rather than quoting the lab sheet as if it were a promise about your living room. There is more on dual-pane and Low-E compatibility here , including the thermal-stress question worth asking before anyone films a large pane.

What you will actually notice

• The room stops being unusable at four in the afternoon. This is the change people report first, and it is really glare plus radiant heat dropping together.
• The hot spot near the glass shrinks. Sitting within a few feet of a big west window stops feeling like sitting in front of a heater.
• Rooms even out. The gap between the sunny end of the house and the shaded end narrows, which often matters more day to day than the peak number.
• Your AC cycles differently. Cooling demand may drop. Whether that shows up on a bill depends on far more than the film.

Choosing for heat

Start with the problem rather than the product. Which rooms are unusable, at what time of day, and what do you want to keep? A west-facing living room with a red-rock view needs a different answer from a south-facing office where nobody cares about the view.

We look at your glass, your orientation and what the room is for, then recommend from the range rather than selling one film to everybody. See the full film range and what each one is for, or residential window tinting for how a home job runs. The consult is free — call 435-233-2398.

Common questions

Does window film really reduce heat?

Yes, it rejects a measurable share of the solar energy hitting the glass. Across the films we install, total solar energy rejected runs from 45% to 84%, measured on 1/4" clear glass; performance differs on dual-pane and Low-E glass. Rejecting that heat may reduce cooling demand, though how much depends on your glass, orientation and shading.

What is TSER?

Total Solar Energy Rejected — the share of the sun's total energy the glass-and-film system turns away, counting visible light, infra-red and ultra-violet together. It is the single most useful number for comparing films on heat, because it accounts for everything rather than one slice.

Is IR rejection the same as heat rejection?

No, and this is where a lot of film marketing gets slippery. Infra-red is only part of the solar spectrum, so a high IR number can sit next to a much lower TSER. A film advertising 90%-plus IR rejection is not rejecting 90% of the heat. Ask for TSER.

Will window film lower my power bill?

It may reduce cooling demand during the months your AC works hardest, which is what most people are really asking. We do not quote a dollar figure or a payback period, because that depends on your home, your equipment and your habits rather than on the film.

Which film rejects the most heat?

Of the range we carry, Reflect Silver 15 rejects the most total solar energy at 84%, measured on 1/4" clear glass; performance differs on dual-pane and Low-E glass. It is also highly reflective, which is a look that suits some buildings and not others — worth seeing on your own glass before deciding.

Do I have to go dark to get heat rejection?

No. Inviso 70 keeps 70% of the daylight and still rejects 45% of total solar energy, measured on 1/4" clear glass; performance differs on dual-pane and Low-E glass. You give up some performance compared with a darker film, but a near-clear option exists.