Guides
Thermal Break Windows in High Heat: Selection Notes
In a hot climate the frame and the glass fail on different counts, and a buyer who fixes one usually pays for the other. The break addresses heat that travels through metal; the glass addresses heat that arrives as radiation. Choosing between them is not the question. The question is how the two are combined on an elevation that faces the sun for most of the day.
Two paths, and only one of them is the frame
Heat reaches a room through the frame by conduction and through the glass by radiation, and the two do not scale together. On a west elevation the radiative load arrives in the afternoon and dominates, which is why a broken frame with a single pane still runs hot. In a shaded courtyard the frame becomes the larger share, because the sun never lands on the glass. Sort the elevation by orientation before choosing hardware for it.
What the break does, and what it does not
The break separates the inner and outer shells of the section so metal no longer touches metal, which slows conduction across the frame. It does nothing about sunlight landing on the glass, and nothing about a sash left open. That is why a broken section belongs with an insulating unit rather than instead of one. On a high-heat project, ask for both, and confirm the break is drawn on the item you are buying.
Pairing the glass with the frame
Standard glazing is 5-20 A-5; single and triple builds are quoted on request, and the 118 casement takes 5-27 A-5 across six chambers. Where the sun lands hardest, a coated or tinted outer pane does more for the load than a thicker cavity. Write the build per elevation, because two faces of one building rarely see the same sun. The cavity is fixed on the order, since the bead is cut to it.
Large lights, height and deflection
Solar control and conduction are irrelevant if the sash bends. A tall light at height takes wind pressure across a long span, so depth and wall thickness come first: the 118 casement runs 118 mm on a 2.0 mm wall, and the 112 casement covers the same wall with a flush-line sash on five chambers. Both hold a wide unit without a heavier sight line. Check the section against the largest module on the elevation.
What the specification should state
Four lines settle a hot-climate order: the break shown on the section for each item, the glass build per orientation, the finish and colour, and the hardware that keeps the sash closed against the gasket. Add the exposure of the site, since a coastal or high-rise position changes the finish recommendation. The reply should carry the dimensional pack as a PDF, with CAD on request, and a sample section before production. Lead time is confirmed with the quotation.
FAQ
Frequently asked
Is a thermal break worth it in a hot climate?
Where the interior is cooled through a long summer, yes, because the inner face of a broken frame stays nearer room temperature and collects less condensation. Where the building is open and shaded the gain is smaller, and the glazing matters more. The break is one part of the envelope, not a substitute for a shaded elevation.
Does a thermal break keep the sun's heat out?
No. It interrupts conduction through the metal. Sunlight entering the glass is a radiative load and is answered by the glazing build: an insulating cavity, a coated outer pane or a tint. A hot-climate specification needs both, and the split between them follows the orientation of each elevation.
Which series suits a high-heat project?
The 118 casement for the largest and most exposed lights, on 118 mm depth, six chambers and a 2.0 mm wall with a 5-27 A-5 unit. The 112 casement covers the same wall on five chambers with a flush line. The 95 series sliding window takes the wide openings on a 1.4 mm wall, where a track is part of the brief.
Can a break be added to a window after it is made?
No. The break is part of the extrusion and the assembly, so it is decided with the section. A window bought without one cannot be converted on site. That is why the item list should state which lines carry a break before the order is placed, rather than being checked at delivery.
What should a supplier show for a hot-climate order?
The section drawing for each item with the break visible, the glazing line and cavity, the finish code and the hardware layout. A sample section and a finished test unit can be reviewed before production. The dimensional pack comes with the quotation as a PDF, CAD drawings on request.
Send your opening schedule
Series, glazing and finish come back as one quotation, with the full dimensional pack on PDF and CAD on request.