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This is an Office News case study: a job written up as it happens. A client has asked for 60-minute fire-rated glazing and a smoke baffle, and asked us to keep the cost down. This page records what we looked at, what the code allows, and what we decided, so the next client with the same question can read it.
The specification calls for glazed openings with a 60-minute fire rating and a glazed smoke baffle, the short glass curtain that hangs from a ceiling to hold smoke back at an opening. Fire-rated glass is one of the most expensive materials on a fit-out, and the price runs from a few dollars a square foot for wired glass to well over a hundred for the multilaminate glass that blocks radiant heat. So before we priced the obvious answer we went through the ladder of products and asked, for each opening, what the code actually requires.
Every fire-rated glass belongs to one of two families, and the 60-minute mark is where they part company.
Fire-protective glass holds back flame and smoke for its rated time but lets radiant heat through. Wired glass and the clear glass ceramics are in this family. It is tested as an opening protective (UL 9 and NFPA 257 for windows, UL 10C for doors), passes the hose-stream test, and is listed for a maximum lite size at each rating. See fire-rated glass.
Fire-resistive glass is tested as a wall (ASTM E119): it holds back flame, smoke and heat, so a person on the far side is protected. It is a multilaminate of several glass lites with intumescent interlayers that turn opaque and insulating in fire, about an inch thick at 60 minutes, and it is glazed in its own framing. It is also the expensive one. Our article on 45, 60, 90 and 120-minute fire glass sets the two families out in detail.
The code turns at 60 minutes. Fire windows in walls take fire-protective glass only up to 45 minutes. Fire doors rated 60 and 90 minutes may carry fire-protective glass, but only about 100 square inches of it per door; any more glass at 60 or 90 minutes has to be fire-resistive. So a “60-minute glass wall” is, by definition, the expensive family, and no product choice changes that. A 60-minute door with a small vision lite, or a 45-minute opening in a one-hour corridor wall, is where value engineering has room.
Wired glass is the oldest fire-rated glass and still the cheapest by a wide margin: a quarter-inch annealed sheet with a welded steel mesh rolled into it. In fire the glass cracks but the mesh holds the pieces in the frame. Its listings are real: 45 minutes in windows up to about nine square feet, and 60 and 90 minutes in doors within the 100-square-inch limit. It withstands thermal shock and the hose stream, and it is available as an insulated unit.
The one thing that changed is impact safety. Plain wired glass is weak, and a person who falls into it is cut by the mesh; since the 2003–2006 code cycle it can no longer be used in doors, sidelites or any other hazardous location unless it meets CPSC 16 CFR 1201. The current products — wired glass with a surface-applied safety film, or laminated wired glass — meet Category II and carry the same fire listings, at a modest premium over plain wired glass and still a fraction of ceramic or multilaminate.
For the smoke baffle it is close to ideal. A baffle is not usually a rated assembly at all; it has to be noncombustible, stay in place under heat, and hold smoke at the ceiling for the minutes it takes the smoke control to work. Wired glass in a steel channel does that, and it is transparent, which is why the client wanted glass rather than a gypsum soffit in the first place.
This is the part of the study that matters, because a wired lite that fails the detail is not cheap, it is unusable.
| Glass | Family | Listings | Limits | Relative cost |
|---|---|---|---|---|
| Safety-filmed wired glass | Fire-protective | 45 min windows; 60/90 min door lites to ~100 sq in | No polished edge, no cutouts, mesh visible, no heat barrier | Lowest |
| Clear glass ceramic (filmed or laminated for safety) | Fire-protective | 20–90 min windows; to 180 min door lites, larger listed sizes | Clear, no mesh; still no heat barrier; edges seamed, no cutouts in the field | Several times wired |
| Multilaminate intumescent glass | Fire-resistive | 45–120 min as a wall, unlimited glass area within the listed frame | Thick, heavy, own framing, long lead time | Highest |
What came in: a request for 60-minute fire-rated glazing at several openings plus a glazed smoke baffle, with an explicit ask to keep the cost down. The openings were described by rating, not by wall type, which is the first thing to fix, because the wall type decides the family of glass.
What we looked at: the three products in the table above, and for each opening whether the code lets a fire-protective lite in at all. Wired glass prices at a small fraction of ceramic and a smaller fraction of multilaminate, so every square foot that can legitimately be wired is a real saving.
What we found: the smoke baffle can be wired glass in a steel channel, and that alone takes the largest area of glass on the job off the expensive list. The 60-minute door lites can be wired within 100 square inches each, but two of the lites as drawn are larger than that and two need a cutout for a lock body, which wired glass cannot take. Any 60-minute opening in a wall that the architect confirms as a fire barrier is fire-resistive glass and stays at full cost; there is no product that changes that.
The decision: wired glass for the smoke baffle and for the door lites that fit the size limit and need no cutouts; ceramic for the lites with cutouts; fire-resistive multilaminate only where the wall rating requires it. We will price it three ways — all-multilaminate as specified, the mixed package, and the mixed package with the two oversized lites reduced to 100 square inches — so the client can see what each choice costs.
Next: confirm with the architect which walls are fire barriers and which are fire partitions, get the lite sizes and hardware preps for every door, and return the three prices. If the design keeps the large 60-minute lites, the answer is multilaminate and the article on fire-rated glass by minutes explains why.
Further entries will be added above as the job moves: the architect’s code path, the three prices, the decision, and the installation.
In fire doors, yes, within a listed lite size of about 100 square inches; in fire windows in walls, wired glass listings stop at 45 minutes. A 60-minute opening with more glass than that needs fire-resistive glazing tested to ASTM E119.
No. The wire mesh runs to the edge, so edges stay cut and must be captured in a frame, and holes, notches and hardware cutouts are not permitted under the listing.
No. Wired glass is fire-protective: it holds back flame and smoke but radiant heat passes through it. Where the code requires a heat barrier, fire-resistive multilaminate glass is required.
Not in hazardous locations such as doors and sidelites: since the 2003–2006 code cycle it must meet CPSC 16 CFR 1201 impact safety, which plain wired glass does not. Filmed or laminated safety wired glass does, and carries the same fire listings.
Fire-Rated Glass · 45, 60, 90 and 120-Minute Fire Glass · Laminated Glass · Commercial Doors · Glass Partitions
Send the drawings, or the door schedule and the wall ratings, and we will tell you which openings can take the cheaper glass and which cannot, and price it both ways.