How to Compare Window Films: Performance Ratings Explained

Why do two films with the same VLT perform differently?

Visible light transmittance says nothing about infrared rejection. Two films can both read 50% VLT while one rejects far more solar heat than the other. Compare SHGC or TSER at the same VLT — that is where ceramic and spectrally selective films separate themselves from simple dyed films.

Are all published numbers measured on the same glass?

No, and this is where quotes get confusing. Initial measured data is typically based on 1/8-inch clear monolithic annealed glass. The same film installed on dual-pane, tinted, or low-E glass will produce different figures. Make sure competing quotes state performance for your actual glass type, not just the headline number.

What is the NFRC label and why does it matter?

The NFRC runs an independent rating and labeling program — manufacturers have no say in how their products are rated. An NFRC label shows U-factor, SHGC, visible transmittance, and air leakage from certified laboratory results. If a product has no NFRC label, it is not certified, and its claims rest on the seller's word. Certified results can be looked up by CPD number in the NFRC Certified Products Database.

What difference does film actually make on typical glass?

NFRC reference data for non-residential single-glazed clear glass shows SHGC dropping from 0.72 to 0.43 with film, and U-factor improving from 1.02 to 0.93. On double-glazed clear commercial glass, SHGC drops from 0.62 to 0.47. Those are reference values, not a promise for your building, but they show the order of magnitude to expect.

Is shading coefficient the same as SHGC?

Not quite. Shading coefficient is an older measure that compares a glazing system's solar heat gain to that of plain clear glass, and it covers only the glass, not the frame. SHGC has replaced it in the fenestration market. If a proposal quotes shading coefficient, ask for the SHGC so you can compare like with like.

How much UV does window film block?

Quality architectural films reject up to 99% of ultraviolet light, which is the main driver of fading in flooring, furnishings, artwork, and merchandise. UV rejection is close to universal across quality film lines, so it is rarely the number that separates one quote from another — SHGC, VLT, and LSG are.

Low Price Window Tint provides published performance data for every film we propose, and we bring samples so you can see the visible light level on your own glass. Licensed California contractor CSLB #1135467, Diamond Certified, serving the Bay Area for over 25 years. Request a free on-site estimate and compare the numbers side by side.