VLT, TSER, IRR: How to Read a Window Film Spec Sheet

Shop for window film in Singapore and you will meet a wall of acronyms: VLT, TSER, IRR, SHGC, UVR. Some sellers lean on this confusion, quoting a single spectacular number and hoping you will not ask what it measures. The specs are actually simple once decoded, and knowing them turns you from a price-taker into someone who can compare quotes on equal terms. Here is each one in plain language, the tricks to watch for, and the questions worth asking any installer.

VLT: how much light gets through

Visible light transmission is the percentage of visible light that passes through the film and glass. A 70% VLT film is barely noticeable; a 15% film reads as a distinct tint. VLT is a preference setting, not a performance score. Lower VLT usually correlates with higher heat rejection, but the correlation is loose: a good spectrally selective film at 65% VLT can outperform a cheap dyed film at 20% VLT, because heat rides mainly on invisible wavelengths, not visible ones.

Practical anchors: above 60% VLT most people cannot tell film is installed. Between 30–40% you get noticeable glare reduction and some daytime privacy. Below 20% is the choice for heavy sun loads, such as west-facing glass.

UVR: and why 420nm beats 380nm

Ultraviolet rejection is usually quoted as "99% UV" or "100% UV", and nearly every film scores well here, so the headline number tells you little. The detail that matters is the cutoff wavelength. Most films define UV as ending at 380nm. But the 380–420nm band just above it, the region covering UVA's tail and HEV (high-energy visible) blue-violet light, still carries enough energy to fade furnishings and contribute to skin photoageing.

Our Meridian Series uses SpectraGuard 420 technology: 100% rejection up to 420nm rather than the typical 380nm, plus up to 70% of HEV blue light cut. When comparing films, ask "100% UV up to what wavelength?" A film rated to 380nm and one rated to 420nm can both print "100% UV rejection" on the brochure while protecting your interior quite differently.

IRR: the number most often gamed

Infrared rejection measures how much of the sun's infrared radiation the film blocks. This is the spec sellers abuse most, because of one detail: at which wavelength was it measured?

The sun's infrared arrives across the whole 780–2500nm band. Films find it easiest to block a narrow slice around 900–1000nm, so a seller can measure only there and print "IRR 99%" while the film lets much of the wider band straight through. A single-wavelength IRR figure is a snapshot taken at the film's most flattering angle.

Two things make an IRR claim meaningful. First, the measurement wavelength should be stated; 1400nm sits in a demanding part of the band, and the Meridian Series posts 97.6–99.2% IRR at 1400nm. Second, look for SIRR (selective infrared rejection), which averages rejection across the full 780–2500nm range instead of cherry-picking one point. If a spec sheet shows a huge IRR and no wavelength, no SIRR and a modest TSER, the IRR number is marketing.

TSER: the one number to compare

Total solar energy rejected is the percentage of all solar energy, visible, infrared and UV combined, weighted by how much of each the sun actually delivers, that the film stops. It is the honest, hardest-to-game summary of thermal performance, because it accounts for the entire spectrum rather than a favourable slice.

This is why a "99% IR rejection" film can have a TSER of only 45%, while another film with less dramatic per-band numbers posts a TSER of 60% and keeps your room genuinely cooler. When two quotes disagree, compare TSER first. Everything else is supporting detail.

SHGC: TSER's mirror image

Solar heat gain coefficient comes from the glazing industry rather than the film industry. It is the fraction of solar energy that gets through into the room, expressed as a decimal, so lower is better. It is roughly the complement of TSER: a film-and-glass combination with a TSER around 60% will show an SHGC in the region of 0.4. If a spec sheet quotes SHGC instead of TSER, you are looking at the same information upside down. Just remember the direction: high TSER good, low SHGC good.

The Meridian Series side by side

Here is how the three tiers read once you know the vocabulary:

Note the pattern: UV and infrared performance are essentially constant across the range, because the nano-ceramic layer does that work regardless of shade. What changes is VLT, and TSER rises as VLT falls because visible light itself carries energy. Choosing a tier is really just choosing how much daylight to trade for heat rejection, which is why room orientation drives the decision. Our HDB guide covers room-by-room selection in detail.

What to ask an installer

Five questions separate serious installers from brochure-readers:

1. "What is the TSER of this film?" If the answer pivots back to a 99% IRR figure, ask again. Anyone selling on a single-wavelength IRR without volunteering TSER is either untrained or hoping you are.
2. "At what wavelength is that IRR measured, and what is the SIRR across 780–2500nm?" You now know why.
3. "Is UV rejection rated to 380nm or 420nm?"
4. "What exactly does the warranty cover, and for how long?" A film's real-world lifespan shows up here. The Meridian Series carries a 12-year warranty against bubbling, peeling, cracking and discolouration, the four standard failure modes of cheap film. A 2-to-5-year warranty is a statement about expected lifespan.
5. "Can you demonstrate the film on a heat lamp with real samples?" Specs predict; a demo proves. Any installer confident in their film will happily let you feel the difference between tiers before you commit.

One more distinction worth knowing: these specs apply to solar films. Privacy films like our Veil Series and clear safety films like the Aegis Series are engineered for different jobs, obscuring sightlines and holding shattered glass together respectively, so judging them by TSER misses the point. If a condo MCST or management office asks about external appearance, VLT and reflectivity are the specs they care about; see our condo window film and MCST rules guide.

FAQ

What is a good TSER for window film in Singapore?

For meaningful cooling in Singapore's climate, look for a TSER above 45% as a floor, and above 55% for sun-facing rooms. The Meridian range spans 45.4% to 64.4% depending on VLT. Treat any quote that leads with a 99% infrared figure but cannot state TSER with caution, as the two numbers describe very different things.

Is 99% infrared rejection better than 60% TSER?

Not necessarily, and often the opposite. A 99% IRR figure may be measured at one flattering wavelength, while TSER accounts for the entire solar spectrum weighted by real solar output. A film can reject 99% of IR at 950nm yet stop under half of total solar energy. TSER is the number that predicts how your room will actually feel.

Does lower VLT always mean better heat rejection?

Within one product family, yes, darker tiers reject more total energy because visible light carries energy too. Across brands, no. A quality spectrally selective film at 66.3% VLT (Meridian 65, TSER 45.4%) can outperform a cheap dyed film at 20% VLT, because dyed films absorb rather than reject and re-radiate heat inward. Compare TSER, not darkness.

What is the difference between IRR and SIRR?

IRR is typically quoted at a single wavelength, such as 1400nm, and shows performance at that one point. SIRR averages infrared rejection across the entire 780–2500nm solar infrared band, so it cannot be inflated by cherry-picking a favourable wavelength. A trustworthy spec sheet states the IRR measurement wavelength and ideally provides SIRR alongside it.

The fastest way to cut through spec-sheet claims is to test films side by side. Book a free on-site consultation and we will bring real Meridian samples and a heat lamp demonstration to your home, so you can feel the difference between tiers on your own glass before seeing a quote. WhatsApp us to arrange a time.