Nothing on an ordinary house survives a direct strike from a strong tornado, so plan for shelter first: an interior room on the lowest floor, or a safe room built to FEMA P-320 and ICC 500. Glass matters in the far more common events below that: straight-line wind and debris.
It's a fair question to ask while standing in a room with three large panes and a warning on the phone. The truthful version of window safety in a tornado starts with a hard fact: in the core of a violent tornado, the windows are not the variable. The roof leaves, and the walls follow. No glazing product sold for houses changes that outcome, and anyone who implies otherwise is selling.
That's not the end of the answer though, because the violent core is a small fraction of what North Texas actually experiences. Most damaging storms here are straight-line winds, gust fronts and debris, plus the outer edges of tornadoes that are weaker than the headline number. Those events are survivable by a normal house, and in those events the building envelope genuinely matters.
So this page separates the two. What to do about the storm that can destroy the house, and what to do about the far more common storm that can breach it.
What actually happened to houses in the 2019 North Dallas tornado?
It's worth using a real local event rather than an abstraction. On October 20, 2019, an EF3 tornado tracked through North Dallas and Richardson. The National Weather Service Fort Worth office documented peak winds near 140 mph along Northhaven Road, 32 minutes on the ground, and a path 15.76 miles long.
The damage figures give the scale: roughly 3,000 homes and 1,000 businesses damaged in Dallas, about 118 structures destroyed, and a total estimated at $1.55 billion in 2019 dollars, which makes it the second-costliest tornado in Texas history behind the 1970 Lubbock tornado and the sixth-costliest in U.S. history.
The number that matters most is the last one: zero fatalities.
Read those together and the lesson is specific. A large number of structures were damaged; a much smaller number were destroyed; and nobody died. That distribution is what a tornado track looks like in practice. The narrow center does catastrophic damage that no residential construction resists. On either side of it, a much wider band of homes takes survivable damage: roof covering stripped, garage doors buckled, fences flattened, trees down, and yes, glass broken by flying debris.
Your house is far more likely to be in the second band than the first. That's where preparation earns its keep, and it's where the honest conversation about glazing lives. In the first band, the only thing that matters is where the people were standing.
Where should people actually shelter, and what is a safe room?
Here is the piece that saves lives, and we do not sell it.
The basic rule is the lowest floor, the most interior room, with as many walls as possible between you and the outside. In most DFW houses that means an interior bathroom, a closet under the stairs, or a central hallway. Get away from all glass, not just the window you were worried about. Take bike helmets for everyone, because head injury from debris is what hurts people in survivable events, and shoes, because afterwards the floor is glass.
Above that baseline, there is a defined engineering answer. FEMA's P-320 publication covers residential safe rooms designed to protect occupants in extreme wind, and ICC 500 is the standard for the design and construction of storm shelters that safe-room criteria reference. A safe room built to those documents is a specific, tested thing, not a marketing description. Options include:
- An interior room retrofitted within an existing house, often a closet or bathroom, with reinforced walls, ceiling and door.
- A prefabricated shelter anchored to the slab in a garage.
- An in-ground shelter in the garage floor or yard.
If you are building or remodeling anyway, this is the moment it costs the least. If you're not, the retrofit versions still exist, and any contractor quoting one should be able to state which standard it is built and anchored to.
The practical part is rehearsal. Everyone should know the room, and be able to get there in the dark, in under a minute, without discussion.
Want an honest read on which of your openings are worth reinforcing? We will walk them with you and say so.
Get My Free QuoteWhy do garage doors and roofs matter more than window glass?
Because that's where the documented evidence points, and it's worth following evidence rather than intuition.
Research from the Insurance Institute for Business and Home Safety has found that wind damage to garage and roll-up doors is strongly linked to adjacent roof and wall damage. In other words, when the envelope is breached at the garage door, the risk of failure elsewhere in the same wind event goes up. IBHS's analysis draws on major events including the 2013 Moore tornado, the 2011 Joplin tornado and Hurricane Ike in 2008.
The mechanism is straightforward. A garage door is by far the largest opening in a typical house, it is a thin panel spanning a wide gap, and it faces the street. Once it fails, wind is inside the structure, pushing up on the roof deck from below while it is already lifting the roof from above. That combination is what takes roofs off.
Window glass is part of the same general story: any large opening lets wind in, and flying debris breaking a window can pressurize a structure. But the documented evidence on cascading envelope failure is about garage doors and roofs, and it would be dishonest to inflate the role of a bedroom window to sell a glazing product. If you have a fixed budget for wind resilience and you spend it on glass while your two-car garage door is unbraced, you have spent it in the wrong place.
Practically: ask about a garage door bracing kit or a wind-rated door, and ask your roofer about sealing the roof deck the next time you re-roof.
What is realistic window safety in a tornado or a strong storm?
Set expectations by the type of event.
In a direct hit from a strong tornado, nothing about the glazing changes the outcome for the building, and the only thing that changes the outcome for people is being in the right room. Glazing decisions are irrelevant at that point. That's the plain truth and it's better to hear it now than from a salesperson in April.
In the far larger population of events below that, the picture is different and glass genuinely matters:
- Debris strikes. Gravel from a neighbor's roof, a fence picket, patio furniture. This is what breaks residential windows in most severe storms, and it happens at wind speeds a house handles easily.
- The aftermath. An open pane during hours of horizontal rain means water damage, ruined flooring, wet drywall and mould. Keeping an opening covered has real value even when the structure was never at risk.
- Injury. Broken glass driven inward is a hazard to anyone in the room who has not reached shelter.
For those events, the options are the same list as any impact problem: laminated glazing built with an interlayer at manufacture, exterior shutters that cover the opening entirely, or security film applied to the existing glass with an attachment system anchoring it to the frame. Each is a genuine option and each has limits. What none of them is, is a tornado rating for a house.
What does security film do and not do in a severe wind event?
Precision matters here, so use the published specifications rather than adjectives.
3M's Scotchshield Ultra S800 measures 8 mils, or 9 once the adhesive is counted. Combined with the Impact Protection Attachment system, its published ratings are GSA and ASTM F1642 blast levels of 2 to 3b depending on glass type and blast pressure, ANSI Z97.1 Class A at 400 foot-pounds, ASTM E1886 pressure cycling to a design pressure of 75 psf either way, and the ASTM E1996 large-missile test.
Read what those ratings are. One fires a piece of lumber at a test assembly; the other applies repeated positive and negative pressure to it. They are laboratory standards developed for windborne debris and blast, and they apply to the film and its anchoring together, not to the film on its own. They are not a tornado rating, because there is no residential tornado rating for glazing. Tornado protection for people is defined by shelter standards, not glazing standards.
What film honestly delivers in a storm below design level is fragment retention and envelope integrity. Glass that fails stays in one piece rather than scattering into the room, and with an attachment system anchoring the filmed glass to the frame, the opening tends to stay closed to wind and rain rather than becoming a hole in the wall. That is a real and worthwhile benefit. It is a different claim from protecting a house against a tornado, and the difference should be stated by whoever is quoting you.
What should I do before the next severe weather season?
None of the highest-value items on this list involve glass.
- Pick the shelter room and rehearse getting to it. Include the pets, because people die going back for them. Keep shoes and helmets in that room permanently, not in a closet elsewhere.
- Set up warnings that will wake you. A NOAA weather radio with an alarm, plus phone alerts with the do-not-disturb override enabled. Most severe events in this part of the country arrive at inconvenient hours.
- Brace the garage door, or price a wind-rated replacement. Given the IBHS findings, it is the most valuable structural item on most DFW houses.
- Ask about the roof deck. At the next re-roof, price sealing the deck and improving the fastening. It's cheap while the shingles are off and impossible afterwards.
- Clear the yard of missiles. Furniture, umbrellas, trampolines, loose fence panels and stacked materials all become debris.
- Photograph the house and store it off-site. Every elevation, the roof, the interior room by room. Do it annually.
- Read your policy for deductible structure and for whether you have replacement cost or actual cash value on the roof. Find that out now, not after.
Then, if budget remains and you'd like the glass to stay in its frame through a survivable storm, that's a reasonable place for it. Just not the first place.
What this looks like in Dallas–Fort Worth
- The National Weather Service Fort Worth office documented the October 20, 2019 North Dallas tornado as an EF3 with peak winds near 140 mph along Northhaven Road, on the ground 32 minutes across 15.76 miles, damaging roughly 3,000 homes and 1,000 businesses in Dallas and destroying about 118 structures, with zero fatalities.
- That storm's damage is estimated at $1.55 billion in 2019 dollars, making it the second-costliest tornado in Texas history behind the 1970 Lubbock tornado, and the sixth-costliest in U.S. history.
- The Insurance Institute for Business and Home Safety has found wind damage to garage and roll-up doors is strongly linked to adjacent roof and wall damage, drawing on events including the 2013 Moore and 2011 Joplin tornadoes and Hurricane Ike in 2008.
- NWS Fort Worth publishes a Tarrant County tornado climatology, but the counts live inside charts rather than in text. Be skeptical of anyone who quotes you a tidy average number of tornadoes per year for your county in a sales conversation.
Questions people ask next
Will window film hold my windows together in a tornado?
Not in a direct strike from a strong tornado. Nothing on a normal house does, which is why shelter comes first. In the far more common storms below that level, film holds a broken pane together and, with an attachment system anchoring it to the frame, helps keep the opening closed to wind and rain. That is the honest limit of the claim.
Should I open windows to equalize pressure before a tornado?
Don't spend your warning time on it. Whatever the pressure argument, the minutes are far better used getting everyone, plus shoes and helmets, into the interior room on the lowest floor. Opening windows also invites wind and rain into the house during a storm you may otherwise have come through intact.
Is a bathroom or a closet the better shelter?
Whichever is more interior, on the lowest floor, and has the most walls between it and the outside. A bathroom adds plumbing walls and a tub to get into. A closet under the stairs adds structure above. Either is far better than a hallway with a glass door at the end of it.
Does a safe room have to be a separate structure in the yard?
No. FEMA's P-320 guidance and the ICC 500 standard cover in-home safe rooms as well as separate shelters, including reinforced interior rooms in an existing house and prefabricated units anchored to a garage slab. Ask any contractor which standard their unit is built and anchored to, and get the answer in writing.
Does film keep broken glass from flying into the room?
That is exactly what it is engineered to do. Safety and security film bonds the fragments of a broken pane into a single sheet rather than letting them scatter. It is the same principle behind laminated glass, applied to glass you already own. It changes how glass fails, not whether it can fail.
What about skylights in a severe storm?
Skylights face upward like the roof does, so they take direct hits from hail and falling debris that wall windows do not. They also sit in the surface that most influences whether water gets into the house. If you are prioritizing spending on glazing for storms, skylights usually deserve attention before a bedroom window does.
Have someone walk the openings with you
We will look at the glass you actually have, tell you which openings are worth reinforcing and which are already fine, and put the recommendation in writing. No pressure either way.
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