What Are TSER, SHGC, VLT, and IR Rejection? Window Film Performance Ratings Explained

Direct Answer

TSER, SHGC, VLT, and IR rejection are four different measurements of how window film interacts with sunlight, and they are not interchangeable. TSER (Total Solar Energy Rejected) and SHGC (Solar Heat Gain Coefficient) describe total heat performance across the whole solar spectrum; VLT (Visible Light Transmittance) describes how much daylight passes through; and "IR rejection" typically describes performance in only a portion of the infrared range, which is why a high IR rejection number does not automatically mean superior overall heat performance.

Key Takeaways

• TSER = Total Solar Energy Rejected: the percentage of incident solar energy rejected by the complete film-and-glass system. Higher is better. TSER = 1 − SHGC.
• SHGC = the NFRC-standardized fraction (0–1) of solar energy that enters as heat, including directly transmitted and absorbed/re-radiated energy. Lower is better.
• VLT = the percentage of visible light that passes through the film. This is about daylight and appearance, not heat rejection.
• IR rejection is often reported on a narrow slice of the infrared spectrum rather than the full infrared range (780–2,500 nm) — the International Window Film Association (IWFA) established IRER (Infrared Energy Rejection) specifically to standardize this measurement across the full range.
• A film can have an impressive-sounding IR rejection percentage while having only moderate TSER/SHGC performance — always compare TSER and SHGC data side by side, not marketing IR claims alone.

Detailed Explanation

Sunlight striking a window contains ultraviolet, visible, and infrared energy. Historically, window film manufacturers reported a mix of different metrics, which made it difficult for buyers to compare products on an apples-to-apples basis. NFRC (National Fenestration Rating Council) standardized SHGC and VLT testing for the broader fenestration industry, and TSER became the window-film industry's preferred summary metric for total heat rejection because it captures the full solar spectrum rather than a single band. TSER is an industry metric, not itself an NFRC-defined term — compare it alongside SHGC and VLT rather than treating it as an NFRC certification.

"IR rejection" claims became a marketing focus because infrared light is associated with heat, and manufacturers can produce high-sounding numbers by testing performance in a narrow band where a given film performs best. The International Window Film Association (IWFA) established IRER (Infrared Energy Rejection), measured across the complete 780–2,500 nm infrared range, specifically to give buyers a standardized, comparable figure instead of narrow-band marketing claims.

Technical Factors

Other related terms worth understanding: UV rejection (percentage of ultraviolet light blocked — most quality architectural films block over 99% of UV in the 300–380 nm range), reflectance (percentage of light/energy reflected off the film surface), absorption (energy retained within the film itself, later re-radiated), and emissivity (a measure of how much a surface radiates absorbed heat — relevant to Low-E-type films like Ecolux 70).

Product Application

Solar Gard publishes TSER, SHGC, and VLT figures for its product lines using NFRC methodology (see the comparison table in Article #1 for TrueVue and PureVue figures). When comparing Solar Gard films to any other product, ask for the same three figures — TSER, SHGC, and VLT — tested under comparable methodology, rather than comparing a marketing IR number to a competitor's TSER.

Limitations / What Buyers Need to Know

• Do not treat a single metric (especially an unqualified "IR rejection %") as the whole performance picture.
• TSER and SHGC describe the same underlying performance from two directions (rejected vs. transmitted) — they are mathematically linked.
• VLT is not a heat metric — a very low VLT (dark film) does not automatically mean superior heat rejection; check TSER/SHGC directly.
• Performance figures are typically modeled for a specific glass thickness/type (e.g., 1/4" clear glass); real-world performance on a different glass type or IGU configuration can vary.

Comparison Table — Reading a Spec Sheet Correctly

Frequently Asked Questions

Which number should I look at first when comparing window films?

Start with TSER and SHGC for heat performance, then check VLT for the amount of daylight and view clarity you want. Treat IR rejection claims with caution unless the tested wavelength range is disclosed, and compare using IRER where available.

Is a 99% IR rejection claim false advertising?

Not necessarily false, but it can be incomplete. It may be accurate for a specific narrow wavelength band while not representing the film's full-spectrum heat performance. Ask for the TSER and SHGC values to get the complete picture.

Do higher TSER films always look darker?

Often, but not always — dual-reflective and ceramic film technologies can achieve strong TSER at a range of VLT levels. Compare the actual published TSER and VLT numbers for the specific product rather than assuming from appearance.

What is IRER and why does it matter?

IRER (Infrared Energy Rejection) is a full-spectrum infrared measurement established by the International Window Film Association (IWFA) to replace narrow-band "IR rejection" marketing claims with a standardized, comparable figure.

Authoritative Sources

• International Window Film Association (IWFA) — TSER, SHGC, VLT, and IRER technical guidance
• European Window Film Association (EWFA) — technical guidance on IR rejection marketing practices
• National Fenestration Rating Council (NFRC) — SHGC/VLT standardized testing methodology
• Solar Gard product technical documentation (TrueVue, PureVue)