Six terms to recognize
Visible light transmission
How much visible light passes through the tested system. Higher means more light. VLT commonly appears as a percentage; VT may use a 0–1 scale. For the same measurement, 0.50 equals 50%. Check whether the result describes film alone or film on stated glass. NFRC’s label guide explains VT.
Total solar energy rejected
The share of total solar energy rejected by the tested filmed glass. Compare the same measurement basis. It is not a cooling-bill forecast. See 3M’s industry definitions.
Solar heat gain coefficient
An architectural rating for solar heat gain through the rated system. Lower values mean less solar heat gain. Ask which reference window system is being rated. NFRC explains the rating.
Glare reduction
A reduction in visible light relative to a reference without the added film. Ask what that baseline was. The number does not establish comfortable visibility in every setting. Definition reference.
Infrared rejection
Ask for the full metric name, wavelength range, and measurement setup. A 3M technical-sheet example defines narrow-band IR rejection separately from broader infrared energy rejection. Neither label should be silently substituted for TSER.
Visible light reflectance
How much visible light is reflected. Check whether the sheet distinguishes the interior and exterior sides, then evaluate the proposed appearance in relevant lighting. Definition reference.
The footnotes are part of the number
Before putting two percentages side by side, identify four things:
- The exact product. Manufacturer, line, shade or finish, and current sheet revision.
- The reference material. Glass type, thickness, coatings, existing tint, and pane construction.
- The measured system. Film alone, film with liner, film on glass, or a complete rated reference system.
- The method. Standard or procedure, relevant wavelength range, and any comparison baseline.
When the basis differs
Mark the comparison “not established” and ask for matching evidence. More decimal places do not resolve a mismatch in what was measured.
A method claim and a certification record are different evidence
If an architectural product is described as NFRC-certified, ask for its applicable record in the Certified Products Directory and the relevant reference system. NFRC’s film program fact sheet describes certification as a defined process; merely naming a test procedure does not demonstrate completion of that process.
Turn the data into better questions
Start with your desired daylight, comfort, visibility, and appearance. Then ask a qualified installer which suitable products meet those priorities on your actual glazing. Keep legal requirements, product suitability, and any protective-performance claims as separate checks with their own evidence.
For announcements about new products or changing industry claims, TintNews covers the news side of the subject. This guide is the place to understand the measurement language behind it.
Sources & review notes
Primary sources support the limited statements attributed to them. Dates below record our check, not the publication date. Manufacturer references are not endorsements.
- 3M: Window Film Industry DefinitionsManufacturer definitions near the end of the page; no publication date shown. No brand recommendation is implied.Checked October 19, 2026
- NFRC: Window Film Certification and Labeling ProgramCertification-body fact sheet; no visible revision date. Used for VT, SHGC, and reference-window context.Checked October 19, 2026
- 3M: Ceramic IR Series technical data sheetRevision B, July 2021. Historical example of glass-specific results and different infrared methods, not current product-selection data.Checked October 19, 2026
- NFRC Certified Products DirectoryLive directory includes an applied-film search. No individual product certification is asserted here.Checked October 19, 2026