Check Film To Glass Compatibility

The chart below helps determine whether a film is compatible with your specific glass by measuring thermal stress—the amount of heat your glass can safely handle once film is applied.

How This Calculator Works Click to expand

Every film and glass combination generates a thermal stress load on the glass. Too much stress and the glass can crack - a phenomenon called thermal breakage. This calculator uses the industry-standard Film-to-Glass stress chart to estimate that load for your specific setup.

Primary Stress

A base score assigned to each film-and-glass combination. It reflects how much additional heat the film traps against the glass. Darker, more reflective films on multi-pane glass carry higher scores.

Additional Stress

Points added based on your site conditions - temperature, altitude, shadows, frame type, pane size, and nearby window treatments. Each factor increases heat buildup or structural risk.

Total Stress Score

The combined score determines the minimum glass specification required for safe installation.

≤ 10

Any Glass

Standard annealed glass is fine.

11-14

Heat Strengthened

Glass must be heat strengthened - roughly twice as strong as standard.

15-18

Tempered Only

Only fully tempered glass can handle this stress load safely.

19+ or NR

Not Recommended

Installation is not recommended regardless of glass type. Some conditions - chipped glass, very large panes, or complex shadow patterns - trigger an automatic NR.

Step 01 Your Glass

Glass Type iNot sure what type you have? Single pane is one layer of glass - common in older homes. Dual pane has two layers with a gap in between - common in most homes built after the 1980s. Low-E glass has a metallic coating and often has a faint blue-green or reflective tint when viewed at an angle. If your glass has a plastic interlayer (like a windshield) and doesn't shatter when broken, it's laminated.

Glass Thickness i1/8" (3mm) is standard for older single pane windows. 1/4" (6mm) is the most common thickness in residential dual pane units. 3/8" (10mm) is used in commercial, storefront, or heavy-duty applications. If unsure, most residential windows are 1/4".

Step 02 Site Conditions

Summer Temperature iPeak summer heat increases the glass surface temperature. The hotter your climate, the more thermal stress film adds. Temperatures above 109°F add additional stress points.

Glass Condition iScratches and chips are stress points in the glass. Film installation adds thermal load, which can cause cracked or chipped glass to fail. Chipped edges are an automatic Not Recommended.

Pane Size iLarger panes absorb more heat overall, increasing total thermal stress. Panes over 100 sq ft are automatically Not Recommended due to the risk of uneven heat distribution.

Gasket Condition iThe rubber gasket lets the glass expand and contract safely with heat. A deteriorated or missing gasket restricts that movement, adding thermal stress risk.

Frame Material iSteel and concrete frames conduct and retain more heat than wood, vinyl, or aluminum, adding stress to the glass. Wood frames require inspection before installing film - check for exposed fasteners near the glass edge, paint buildup, warping, and deteriorated glazing compound. When in doubt, consult a glazier.

Shadow Type iShadows create uneven heating across the glass - the shaded area stays cool while the sunny area heats up. The more irregular the shadow shape, the greater the thermal differential and stress. "T" or "V" shaped shadows add 3 stress points - the highest value in this category.

Altitude iHigher altitudes mean more intense solar radiation due to thinner atmosphere. This increases the heat absorbed by the glass and film, adding to the overall stress score.

Window Treatment iBlinds, curtains, or shades placed close to the glass trap heat between themselves and the window. This increases the temperature at the glass surface and adds 1 stress point if within 4 inches.

Films Safe for Your Glass

Additional Stress -

Awaiting your selections Complete steps 1 and 2 above to see which films are compatible with your glass.

Fill in all fields above to see results

Requires Stronger Glass

Not Compatible

Note - This calculator is a guide based on manufacturer film-to-glass stress charts. Results are informational only. Flexfilm is not liable for glass breakage and/or seal failure. When in doubt, have your glass verified by a licensed glazier before installation.

Choose the Right Film Without Guessing

Why It's Important

Window film changes how heat interacts with glass.

Pick the wrong film and you risk cracking the glass or ruining the seals.

Learn more about glass safety

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