Frit or coating? Two ways to make glass bird-safe.
What each looks like from the room, and how each is rated.
Vistaza Engineering · Nov 10, 2022 · Updated Sep 17, 2026 · 4 min read
Bird-safe glass carries a pattern that birds can see. There are two common ways to put it there. A ceramic frit is visible to birds and to people. A pattern in an ultraviolet-reflective coating is visible to birds and close to invisible to people. Both are rated the same way, by threat factor.
Why birds hit glass.
Birds do not read glass as a surface. They see the sky or the trees reflected in it and fly toward them. Or they see straight through a glazed corner or a glass railing to the open space beyond. The American Bird Conservancy puts the toll at more than one billion birds a year in the United States alone.
The fix is the same in every case. Give the bird a pattern it can detect, close enough together that it does not try to fly between the marks.
Frit: a pattern you can see.
Frit is ceramic, printed on the glass as closely spaced dots or lines and fused to the surface in the furnace. It is permanent. Birds see it. So do the people in the room, and so does anyone looking at the facade.
That is the trade. The more visible the pattern, the less the glass reads as clear. Dots and lines come as stock patterns, and a custom pattern can be made to suit the building. Stock costs less than custom.
Coating: a pattern birds can see.
Birds see ultraviolet light. People do not. A UV-reflective coating laid down in a pattern gives the bird a clear signal, while the glass stays close to clear from the room and from the street.
This is the choice when the view matters most, such as living rooms, hotel rooms and ground-floor amenity spaces.
| Question | Ceramic frit | Pattern in the coating |
|---|---|---|
| What people see | A fine pattern of dots or lines | Close to clear glass |
| What birds see | The pattern | The pattern, in ultraviolet |
| How it is made | Ceramic fused to the glass | UV-reflective coating applied in a pattern |
| ViBird threat factor | 20 to 25, by pattern | 12 |
How each is rated.
The threat factor, or TF, was developed by the American Bird Conservancy. It comes from flight-tunnel tests with live birds, which are given a choice between the test glass and plain glass. The scale is read like this:
- A low score means birds saw the glass and avoided it.
- A score around 50 means the pattern made no real difference.
- A score above 50 means the material may add to collisions.
The Conservancy treats a material as bird-friendly at a threat factor of 30 or less, which it links to at least half as many collisions.
A threat factor belongs to the assembly that was tested. That means the glass, the pattern, and which surface the pattern sits on. Ask for the TF of the makeup you are buying, not of a similar one.
A threat factor belongs to the tested assembly, not to the word bird-safe.
What New York City asks for.
Local Law 15 of 2020 is the rule most mid-rise teams meet first. In outline:
- Bird-friendly materials are required on the building envelope up to 75 feet above grade. Within that zone, other materials may not add up to more than 10 square feet in any 10-by-10-foot area.
- The threat factor must be 25 or less, as assigned by the American Bird Conservancy. The building code section is BC 1403.8.
- Glass that creates a hazard is covered at any height. That includes fly-through conditions such as glazed corners, and installations such as glass railings.
- It applies to new buildings filed on or after January 10, 2021. Existing buildings are covered when an alteration replaces all of the exterior glazing.
The drawings have to show it. The elevations mark the bird-friendly areas. Diagrams show any fly-through conditions. A table lists each material or window assembly with its threat factor.
Other cities have their own rules. Check the local law before you assume the New York numbers apply.
What it costs, and how to keep that down.
Patterned glass costs more than plain glass. How much more depends on the type, whether the pattern is stock or custom, the sizes and the quantity. The practical saving is scope. The rule covers part of the building, so mark the openings it covers and price bird-safe glass for those only.
Films and decals exist for retrofits. They are a fix for an existing facade, not a specification for a new one. Screens, exterior shading and overhangs also reduce reflections, and they can work alongside the glass.
Still a high performance window.
ViBird is Vistaza's bird-safe glass. The pattern is one layer in the same insulated glass unit as every other Vistaza window, so the window still carries a U-factor, an SHGC and a sound rating. Each ViBird type lists its own.
The ViBird types, and how the threat factor scale works, are on the ViBird page. To find out which openings on your building the rule covers, send the plans.