TRUSTED BY THOUSANDS OF DIY HOMEOWNERS
TRUSTED BY THOUSANDS OF DIY HOMEOWNERS
When it comes to choosing the right window film, the performance numbers can be confusing. What does SHGC actually mean? Is a higher or lower VLT better? And what is TSER anyway? At Concord Window Film, we believe the best purchasing decisions start with understanding what these metrics measure and how they relate to your specific goals — whether that’s reducing heat, cutting energy costs, blocking glare, or protecting your furnishings from UV damage. This guide breaks down the three key window film performance metrics defined by the National Fenestration Rating Council (NFRC) and explains exactly how to use them to evaluate and compare films.
Window film performance is evaluated using three key metrics defined by the National Fenestration Rating Council (NFRC) and the International Window Film Association (IWFA):
In general, the darker the film, the better its heat performance — but the right choice depends on your climate, window orientation, and personal preference for light levels.
Before diving into the metrics, it helps to understand who defines them.
The National Fenestration Rating Council (NFRC) is a nonprofit organization that provides standardized, accurate performance ratings for windows, doors, skylights, and window film. Most professional-grade films — including Concord Window Film’s ComforTech™ Ceramic Series — are NFRC certified.
The International Window Film Association (IWFA) is the trade association for the window film industry. They support education, best practices, and performance standards for both professionals and consumers. TSER, in particular, is a metric commonly defined and promoted by the IWFA.
Both entities promote energy efficiency and help consumers compare products on a level playing field.
All solar control window film works by preventing solar energy from entering the home in one of two ways:
Most high-performance ceramic films (like our ComforTech™ series) use a combination of both. Understanding this is important because the performance metrics below measure different aspects of this process.
Here’s a quick video that illustrates how our ComforTech™ 25 works on clear glass to block the sun’s energy:
With that understanding under our belt, let’s look at the main criteria used to evaluate the effectiveness of window film:
What it is: VLT is the percentage of visible daylight that passes through the window after film is applied.
How it works: A film with a VLT of 35 allows 35% of visible light through and blocks 65%.
The scale: VLT runs from 0% (completely opaque) to 100% (perfectly clear). For solar control film, typical residential values range from 5 to 50.
Important note: Films are not as dark as the VLT number suggests. Our ComforTech™ 45 — which blocks 55% of visible light — looks nearly invisible on the glass. We always recommend ordering a sample kit to see the film in your own space before purchasing.
At Concord Window Film, we offer a variety of VLT options to meet your unique lighting and visibility needs. Specifically, our ComforTech™ Ceramic Series Window Film comes in five shades which roughly correspond with each of the film’s VLT:
| Film Name | VLT |
| ComforTech™ 45 | 45 |
| ComforTech™ 35 | 35 |
| ComforTech™ 25 | 23 |
| ComforTech™ 15 | 15 |
| ComforTech™ 05 | 7 |
| Silver 15 Reflective | 16 |
It may seem unintuitive, but in the case of the Visible Light Transmission metric, the smaller the number, the darker the film and the better the solar control performance of the film.
A common worry folks have when they hear a film only lets in 45% of visible light is that the film will make the house too dark. The reality is that the films are not as dark as they sound. Our ComforTech™ 45 which is our lightest film blocks 65% of visible light – yet it looks almost invisible on the glass.
Solar control window film will make your house darker inside, but the effect is not as dramatic as one would believe just looking at the VLT numbers. We typically recommend getting a window film sample kit and taping the samples to one of your windows to see what the film will look like on your glass.
What it is: SHGC is the NFRC’s primary measurement for heat control. It measures how much total solar heat — both directly transmitted and re-radiated inward after absorption — enters the home through the filmed window.
How it works: SHGC is expressed as a number between 0 and 1. A film with an SHGC of 0.25 allows 25% of solar heat to enter the home and blocks 75%. The lower the number, the better the heat control.
What is a good SHGC for window film? For residential use, an SHGC below 0.40 is considered good heat control. Below 0.30 is excellent and appropriate for hot or sunny climates. Below 0.25 is high-performance, suitable for south- or west-facing windows in warm regions.
Below is a chart of the Solar Heat Gain Coefficient for our solar control films:
| Film Name | SHGC |
| ComforTech™ 45 | .48 |
| ComforTech™ 35 | .41 |
| ComforTech™ 25 | .31 |
| ComforTech™ 15 | .25 |
| ComforTech™ 05 | .18 |
| Silver 15 Reflective | .21 |
A window film with a SHGC of 0.25 allows 25% of solar heat to enter, while rejecting 75%. Lower SHGC values indicate better performance in blocking solar heat.
The NFRC rates SHGC values through standardized testing. Choosing a window film with a low SHGC is essential for achieving better thermal performance. You can learn more about these metrics at the NFRC official website.
What it is: TSER measures the total percentage of solar energy — including visible light, infrared, and UV — that is blocked (reflected and absorbed) by the film. It is essentially the inverse of SHGC, expressed as a percentage.
How it works: A TSER of 69% means the film rejects 69% of the sun’s total energy. The higher the percentage, the better the solar control performance.
What is a good TSER for window film? A TSER of 50% or higher is a reasonable baseline for heat control. Above 65% is high performance. Above 75% is exceptional and suitable for the most demanding applications (hot climates, south-facing windows, sunrooms).
Why it matters:
Below is a chart of the TSER for our ComforTech Ceramic Series films:
| Film Name | TSER |
| ComforTech™ 45 | 51% |
| ComforTech™ 35 | 58% |
| ComforTech™ 25 | 69% |
| ComforTech™ 15 | 75% |
| ComforTech™ 05 | 82% |
| Silver 15 Reflective | 79% |
TSER is often our go-to metric we use when talking about solar protection. It gives the same information as the SHGC, but in a more straightforward and non-technical (coefficient!?) way.
The right film depends on your goals — every film in the ComforTech™ Ceramic Series blocks meaningful solar heat. Use this guide to match the metric to your situation:
| Metric | What It Measures | Direction | What to Know |
|---|---|---|---|
| VLT | Visible light through film | Personal preference | Lower VLT = darker film = stronger heat performance. All ComforTech™ films range from 7% to 45% VLT. |
| SHGC | Solar heat entering home | Lower is better | All ComforTech™ films have an SHGC between 0.18 and 0.48 — compared to 0.82 for untreated clear glass. Every film delivers meaningful heat reduction. |
| TSER | Total solar energy blocked | Higher is better | ComforTech™ films range from 51% to 82% TSER. Even our lightest film (ComforTech™ 45) blocks 51% of total solar energy — nearly 4x more than untreated glass at 14%. |
The key trade-off is light vs. heat, not good vs. bad. All ComforTech™ films provide substantial solar protection compared to untreated glass. The choice between shades comes down to how much natural light you want to preserve. A ComforTech™ 45 is ideal for someone who wants near-invisible film with solid heat reduction; a ComforTech™ 05 is for someone who prioritizes maximum performance and doesn’t mind a darker appearance.
Performance needs vary significantly depending on where you live and how your home is oriented. Use this as a starting guide:
| Situation | Prioritize | Best Film Range |
|---|---|---|
| Hot/sunny climate (FL, TX, AZ, CA) | Low SHGC (<0.25), High TSER (>70%) | ComforTech™ 05 or 15 |
| Mixed climate (Mid-Atlantic, Pacific NW) | Moderate SHGC (0.30–0.45) | ComforTech™ 25 or 35 |
| South- or west-facing windows | Low SHGC, lower VLT | ComforTech™ 15 or 25 |
| North- or east-facing windows | Higher VLT acceptable | ComforTech™ 35 or 45 |
| Home office / glare reduction | Low VLT (15–25) | ComforTech™ 15 or 25 |
| Balance of light and privacy | VLT 25 | ComforTech™ 25 |
| Maximum privacy + heat control | Low VLT, high TSER | ComforTech™ 05 or Silver 15 |
| Retail / display windows | High VLT, UV rejection | ComforTech™ 45 |
Window direction matters: Windows that receive direct sun for longer periods — typically south- and west-facing in the Northern Hemisphere — benefit most from lower VLT and higher TSER films. North-facing windows may not need as aggressive a film.
Questions about your specific situation? Give us a call to discuss! 1-888-206-1413.
VLT, SHGC, and TSER are the three primary metrics for evaluating solar control film, but a complete specification sheet will also include:
For complete specifications on all Concord Window Film products, see our full performance specification chart.
If you have any questions about any of the performance measurements, you can reference our window film glossary here.
Evaluating window film comes down to understanding three core metrics: VLT measures light transmission, SHGC measures heat entering the home, and TSER measures total solar energy blocked. Together, they give you a complete picture of how a film will perform.
The right film is always a balance between performance and personal preference. Darker films offer better heat rejection, but the optimal choice depends on your climate, window orientation, and how much natural light you want to preserve.
At Concord Window Film, we recommend starting with a sample kit so you can see the difference in your own space before committing. And if you have questions about which film is right for your situation, we’re always happy to help — by phone at 1-888-206-1413, via chat, or by email at [email protected].
