Reason 1: the building code — hazardous locations
For homes in the United States, safety glazing is set by the International Residential Code (IRC), section R308.4, as adopted by each state or city. It names hazardous locations where glazing must be safety glazing (in practice, usually tempered). In summary:
- Doors. Glazing in fixed and operable panels of swinging, sliding and bifold doors.
- Next to doors. Glazing within a 24" arc of either vertical edge of a door in the closed position, where the bottom exposed edge is less than 60" above the floor or walking surface (with exceptions — for example, a door to a shallow closet).
- Large, low windows. An individual fixed or operable pane that meets all four conditions: exposed area larger than 9 sq ft, bottom edge less than 18" above the floor, top edge more than 36" above the floor, and a walking surface within 36" horizontally.
- Wet areas. Glazing in walls enclosing tubs, showers, hot tubs, saunas and steam rooms where the bottom exposed edge is less than 60" above a standing or walking surface.
- Stairs, landings, ramps, pools and railings. Glazing close to stairways, landings and ramps, near pools and spas, and all glazing in railings, each with its own dimensions.
Each of these has exceptions (a protective bar at the right height, decorative glazing, openings too small for a 3" sphere, among others), and they change between code editions — check the edition your market uses.
Why the configurator can't decide this one alone
Look at the list again: almost every condition depends on where the window is installed — next to a door, beside a tub, near a stair — not on the window itself. The only condition a configurator can measure is the pane's area, and even the "large, low window" rule needs to know the sill height and the floor. So code-driven tempering belongs to the person who knows the opening:
- Offer tempering per sash and per lite, not just per window — "tempered bottom sash only" is a common, legitimate order on a hung window next to a tub.
- Let a dealer or rep mark the opening (beside a door, in a wet area) and turn that into the right tempered lites.
- Never silently drop a tempered selection somebody made, even if the window is later resized.
Reason 2: the glass is too big to make annealed
The second reason has nothing to do with code. Sealed-unit makers and glass suppliers publish limits: above a certain area (or aspect ratio, for a given thickness) they will only supply the lite tempered. At our launch plant the line is 30 sq ft of glass in a single lite — anything over it is made as a tempered unit. This one the configurator can and should decide on its own, because it depends only on the size.
Five rules for automatic size-based tempering
- Measure each lite, not the window. The limit applies per lite, so a large picture window may be over it while the operable beside it in the same mull is not. Measure each opening of a mull at its built frame size, not its centerline size (see sizing mulled windows).
- Strictly over the limit. A lite exactly at the limit stays annealed — write the rule as "greater than", and test the boundary.
- Compute it; don't store it. If the tempering is written onto the line as if somebody picked it, resizing the window below the limit leaves the customer paying for tempered glass they no longer need. Work it out from the size every time, and keep a person's own tempered pick separate so it is never taken away.
- Price it and order it from the same answer. The tempered lite must appear on the quote, on the glass order and on the purchase order to the supplier from the same rule. If the price says tempered and the glass order says annealed, the plant cuts glass it cannot use.
- Say why. Show "Tempered (required: lite over 30 sq ft)" on the line, so a rep can explain the charge and nobody "corrects" it.
Where tempered glass goes next
Most window plants cut annealed glass in house and buy tempered units from their IG supplier. That means a tempered lite must be kept off the cutting table's file and put on a purchase order instead — and when a batch is sent to the optimizer again, the rule must still hold. It still needs its own label and its own scan at the glass bench, because it is still one of the window's sealed units (see one label per sealed unit).
How Extrusia handles it
Tempering by hand is offered per window or per sash (bottom only, top only), and is never removed by anything automatic. Size-based tempering is a rule on the series — "a lite over 30 sq ft is tempered" — evaluated for every lite of every opening, on every quote, reprice and order. It overrides an annealed pick, prints its reason on the line, and flows through the same function to the bill of material, the glass order, the supplier purchase order and the stickers. Tempered lites are never written to the cutting table's file.