Does Window Film Help in an Earthquake? What FEMA and the Test Data Say

Window film gets mentioned in earthquake conversations often enough that it is worth separating what it can plausibly do from what it cannot. The short version of our reading: film may help hold broken pieces together, it is not what keeps the glass from breaking, and the sources do not agree on how it should be attached.

Start with the cause. FEMA's guide to nonstructural earthquake damage, FEMA E-74, says glazing is "particularly vulnerable in flexible structures with large inter-story drifts," and that large storefront windows are also vulnerable. Drift is the sideways movement of one floor relative to the next. A window frame is bolted to the building, so when the building sways, the frame is pushed out of square. FEMA's NEHRP commentary (FEMA P-750) describes the geometry: the rectangular frame becomes a parallelogram, and the glass breaks when its edge contacts the frame. The window film industry association (IWFA) says the same thing in its education guide: the major cause of breakage in a seismic event is movement of the glass in relationship to the frame and building.

We did not find any source saying film changes how far the frame moves or how much clearance the glass has. Film is applied to the glass. The frame is a separate question, and in a building with large drift the frame is where the problem starts.

The film passage in E-74 is short and carefully hedged. It says plastic films that help hold glass fragments together are available, and that these films "may reduce seismic risk associated with dislodged fragments." It says strategic application where glazing is over an exit way, within 10 feet of one, or along interior corridors "may provide sufficient risk reduction" if the areas around the building have limited public access. It also says extending the film over the edge of the frame "is advisable not only to hold broken fragments in place but also to prevent the entire pane from falling out."

Read the verbs: may reduce, may provide. FEMA does not call film a fix, and it does not list it first. For storefront glass, E-74 puts laminated glass ahead of film: "Laminated glass will typically remain in place when broken and will prevent people or objects from falling through the opening." Film is the option for existing panes you are not replacing. For the difference between film and laminated glass in general, see our film, laminated glass and replacement comparison. And film does not turn ordinary glass into safety glass; our post on whether window film is safety glass explains the legal definition.

E-74 also lists steps that have nothing to do with film. It says "Liberal use of landscaping strips or areas with restricted pedestrian access may help to reduce the seismic risk beneath large glass panes or tall curtain walls," and "Avoid placing beds, desks, chairs or couches that are typically occupied many hours a day near large plate glass windows." Moving a desk away from a big window costs nothing and sits in the same FEMA passage as the film advice.

Two California public sources point the same direction. The state Seismic Safety Commission homeowner's guide (2005 edition) says that "large windows can be made safer by applying plastic film on them," after noting that a professional can advise on weaknesses. The Earthquake Country Alliance large windows page lists film among several fixes, after steel framing or plywood paneling and added mullions, and says to consult a qualified architect or engineer if you have large or numerous windows, especially on the ground floor. Both say "safer," not "safe."

Daylight film stops a small gap short of the frame edge. Attached or anchored film is held at the frame with sealant or a mechanical system. IWFA describes daylight as the most widely used method, and says tempered glass needs a "more robust method" than daylight because it breaks into small pieces. What the sources say about earthquakes in particular does not line up neatly:

• FEMA E-74 advises extending film over the frame edge, to hold fragments and keep the whole pane from falling out.
• Madico, a film manufacturer, says on its natural disaster page that it does not recommend "a simple daylight installation of safety film" for earthquakes, and recommends anchoring systems. That is a manufacturer's position; the page shows no test data for it.
• IWFA reports its own testing that included an anchored system, which it says significantly improved glass retention when anchored from the top of the window. We did not find a published report for that testing.
• UCSD found the opposite side of the trade-off. Wet-glaze attachment, the one method it tested, lowered the drift at which the glass cracked or fell out, by about 32% and 37% on average for two damage states, because the attachment stiffens the system and concentrates stress along the glass edge. But "The attachment system, when it did not fail, held the shattered panel in place after testing."

These sources answer different questions. UCSD measured when the glass failed; E-74 and Madico are concerned with whether broken glass stays in the opening. Wet glaze was the only attachment method UCSD tested, so its result says nothing about mechanical anchors. We are not going to give you a rule here, because the sources do not give one. Whether a given opening should be daylight or attached depends on the glass, the frame and the hazard, and you should ask for the test basis for that exact setup. Attachment also comes up in a different hazard; our blast mitigation page covers why anchoring is discussed there.

The California guide on nonstructural earthquake hazards in schools (Cal EMA, DSA, Seismic Safety Commission and Department of Education, revised 2011) covers windows in a single entry. It says glass next to or within entrance or exit doors must be safety glass, meaning tempered or laminated, warns that fallen glass can injure people or block exits, and recommends: "Replace glass on door and glass surrounding the door with safety glazing." The word film does not appear in it.

FEMA P-1000, FEMA's school safety guide, does not discuss window film for earthquakes either. It points to the California guide and to E-74, and says a thorough evaluation is best prepared by an earthquake design professional. If you run a district, the state guide's own answer for exit-door glass is replacement with safety glazing. For how film is considered for school security, see our post on security film for schools and districts; it is a different question from earthquake performance.

• Glass type, thickness and size for each opening, and whether it is annealed, tempered, laminated or insulated.
• Daylight or attached, and why. If attached, which method, and what test supports it for your frame and glass.
• The test basis for that exact configuration. A brochure is not a test report, and a lab result on one window type is not a result for another.
• Who assesses the frame. Drift capacity is an engineering question, and E-74, P-1000 and the state guides send it to an architect or engineer.
• What the film is not claimed to do, in the written proposal.

Our posts on what to ask a window film installer and what a site assessment should cover go through the questions in more depth. If you want us to look at your openings, contact us and we will tell you what we think the evidence supports for each one.

1. FEMA E-74, Reducing the Risks of Nonstructural Earthquake Damage, 4th ed. (2012), Section 6.3.1.4, Glazing, as hosted by the ATC project site. Link.
2. FEMA P-750, 2009 NEHRP Recommended Seismic Provisions, commentary on ASCE 7 Section 13.5.9. Link.
3. FEMA P-1000, Safer, Stronger, Smarter (2017), state-hosted copy. Link.
4. Eva and Hutchinson, UC San Diego SSRP 09-02, Experimental evaluation of the in-plane seismic behavior of store-front window systems (2009), funded by the AIMCAL Window Film Committee; copy hosted by a film manufacturer. Link.
5. International Window Film Association, Safety & Security Education Guide (2026). Industry source. Link.
6. Madico, natural disaster mitigation page. Manufacturer statements. Link.
7. 3M, Safety S70 technical specifications, Revision D (January 2025). Manufacturer statements. Link.
8. California Building Code, Chapter 24, as reproduced on UpCodes (unofficial text; confirm with the official code). Link.
9. DSA IR 24-2, Window Wall Systems (2016 CBC). Link.
10. California Seismic Safety Commission, Homeowner's Guide to Earthquake Safety (2005). Link.
11. Earthquake Country Alliance, Large Windows. Link.
12. Cal EMA, DGS Division of the State Architect, Seismic Safety Commission and Department of Education, Guide and Checklist for Nonstructural Earthquake Hazards in California Schools (revised January 2011). Link.