Windows

Windows in a PEB envelope

Windows in a pre-engineered steel building provide daylight, views and, if operable, ventilation. In warehouses and factories they are often limited to a strip at eye level or high-level clerestory windows, while offices, showrooms and amenity areas use larger glazed areas. Unlike in masonry construction, a window in a metal-clad wall is not carried by the wall itself: it sits in a framed opening supported by girts and jamb members, and it must be weather-sealed to a profiled sheet. This makes coordination between the window supplier and the steel detailer essential.

Window types and options

Frames are typically aluminium (powder-coated or anodised), uPVC, or steel. Glazing options include clear or tinted float glass, toughened (tempered) or laminated safety glass, insulated glass units (IGU) with low-E coatings for thermal performance, and polycarbonate where breakage is a concern.

Sizing and performance

• Module to the girts. Window heights that fit between two girt lines (often 1.0–1.5 m apart) avoid cutting girts and adding headers. Widths are usually chosen to suit the bay spacing and wall sheet cover width.
• Wind pressure. Windows must be rated for the components-and-cladding design pressure of their wall zone; corner zones are higher. See wind design.
• Water and air. Specify water penetration and air infiltration ratings to suit the exposure; tropical and coastal sites need higher water ratings.
• Energy. In regions with energy codes, window U-value and solar heat gain coefficient count toward compliance of the whole envelope, together with insulation.
• Safety glass is required in many locations (near doors, low sills) by building codes.
• Daylight vs heat. In hot climates, large unshaded windows increase cooling load; roof skylights often deliver more uniform daylight to deep plan buildings.

Performance ratings and glazing standards

Windows are bought as rated products. Asking the supplier for the rating against the correct standard is the simplest way to make sure a window will survive the site wind and stay watertight.

• Typical PEB windows: aluminium sliding or fixed windows in a light sub-frame, set between two girt lines with a head flashing, sill trim and jamb trims; steel-framed louvre windows in tropical amenity blocks; and fixed polycarbonate strips where breakage is a risk.
• Condensation: thermally broken aluminium frames or uPVC are preferred where the building is air-conditioned in a humid climate, or heated in a cold one.
• Security: low-level windows in warehouses are often omitted or fitted with grilles; high-level clerestory windows give daylight with less risk.

Framing, flashing and installation

The steel framing consists of jambs between girts, with the girts themselves often acting as head and sill. The window is fixed to a sub-frame or to the framing members through its own fixing lugs, never directly to thin sheeting. Weather-tightness relies on a head flashing that laps under the wall sheet above, a sill flashing with a drip edge, and jamb trims with profiled closures and sealant, following the rules in trims and flashings. Isolate aluminium frames from coated steel with tapes or gaskets. In insulated walls, the window frame should align with the thermal line to limit condensation.

Maintenance and WSC supply

Clean glazing and drainage slots in the frame, replace failed gaskets and sealant, and check operating hardware. Damaged sill flashings should be repaired promptly because water entering at windows can run down inside the wall and corrode base trims and girts.

World Steel details window openings, jambs and trims on the wall framing drawings and supplies windows together with doors in its doors and windows packages under the accessories scope; projects with local glazing contractors receive full opening dimensions and fixing details.