Can a safety film applied to existing glazing withstand a hailstorm? The answer depends on an essential distinction that is rarely made explicit: absorbing the kinetic energy of an impact and retaining glass fragments after breakage are two different mechanisms. A safety film acts effectively on the second and partially on the first. This distinction is critical when assessing whether the solution is suitable for a particular exposure scenario.
Hail as a mechanical stress on glazing
Hailstone size is the determining factor: combined with impact speed, hailstone mass defines the kinetic energy transferred to the glazing. Below a moderate diameter, most single glazing withstands the impact without breaking. Above that threshold, unreinforced single glazing may fail under the impact pressure, creating a risk of glass fragments being projected into the building.
In mainland France, the south-west, the Île-de-France region and the Alpine corridors are among the areas most exposed to severe hailstorms. Department-level Tempête-Grêle-Neige (TGN) claims data confirms the geographical concentration and increasing recurrence of these events.
What a safety film actually does when impacted
A safety film consists of one or more layers of optically clear, high-quality polyester bonded with a pressure-sensitive adhesive. Its mechanical properties—thickness and break strength—determine how it behaves under impact.
Fragment retention. This is the primary, documented function of a safety film. When an impact breaks the glass, the fragments remain attached to the film. EN 12600 sets out these performance requirements through standardised pendulum impact tests. Some films in the Solar Screen range achieve EN 12600 classification 2B2—certified separately for each tested product and thickness—ensuring fragment retention even after complete glazing breakage. In a hailstorm, this reduces the risk of injury and provides partial protection against fragments entering the building.
Partial absorption of kinetic energy. A thick film (from 310 µm) can absorb part of the impact energy as its polyester layers undergo elastic deformation. This may delay or reduce glass breakage under low- to medium-intensity impacts. However, this capability is not sufficient to make ordinary glazing equivalent to approved anti-hail laminated glass.
Thickness and strength: Solar Screen range data
The Solar Screen safety range includes films from 125 µm to 485 µm thick, with break strength ranging from 28 to 61 kg/cm (specifications published on the range page). These figures support a rational choice based on the level of exposure:
- 125 µm / 28 kg/cm: reliable fragment retention, limited impact absorption. Suitable for everyday risks.
- 210–240 µm / 34–40 kg/cm: increased resistance to moderate impacts. Recommended for areas with intermediate exposure.
- 310–485 µm / 61 kg/cm: maximum protection available from an adhesive film. Relevant for areas with high exposure or large glazing surfaces. The CLEAR 17 C (485 µm), certified to EN 356 class P3A (BCRC test report no. 2025B SEC 49837-3), delivers the highest performance level in the range.
For the full list of products and their mechanical properties, the complete Solar Screen safety film range provides details of certifications, thicknesses and installation requirements.
Limitations every installer should explain clearly
Regardless of its thickness, a safety film cannot prevent single glazing from breaking when struck by large hailstones or subjected to repeated impacts. Several factors can reduce its effectiveness or make application unsuitable:
- Large hailstones and repeated impacts: beyond a certain cumulative kinetic energy threshold, the glass will break completely. The film retains the fragments but does not preserve the glazing's watertightness.
- Previously damaged glazing: a film applied to cracked glass or glass with micro-fractures does not restore the glass's structural strength. It must be applied to glazing in good condition.
- Water ingress after breakage: even when fragments remain retained, water may enter if repeated impacts penetrate the film or cause it to peel away.
- Confusion with approved anti-hail glazing: a safety film reinforces existing glazing; it is not an equivalent-performance replacement for certified anti-hail laminated glass.
Safety film or glazing replacement: which option is right?
The cost of installing film on existing glazing is significantly lower than replacing it with laminated insulating glass. A film is a relevant option in the following situations: glazing in good condition, exposure to moderate-sized hail, budget constraints or an inability to undertake work in the short term, such as in an occupied building or rental property portfolio.
When a building is located in a very high-exposure area and previous events have already weakened the glazing, replacement with certified glazing is the structurally consistent response. In that situation, a safety film may serve as a temporary measure until the work can be completed.
To understand how adhesive safety films perform in a broader range of impact scenarios—including accidental impacts and attempted break-ins—the article on anti-shatter film for building safety explains the general mechanisms and documented use cases.