Fiberglass windows come of age

Performance class and grade

Many fiberglass windows are rated at CW-PG50 or above. Performance class (commercial [CW]) and performance grade 50 means one can get floor-to-ceiling fixed windows with thin mulls of 13 or 25 mm (0.5 or 1 in.) aluminum, depending on the overall size of the window. Based on American Society of Civil Engineers (ASCE) 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, structural performance calculations show fiberglass windows can exceed 30 stories in most areas. This matches the look of aluminum and is something that cannot be achieved with lower performance vinyl.

Fire rating

Fiberglass windows are generally not fire rated. Always check with the window manufacturer on fire rating for frames and glazing.

Installation

Fiberglass windows can usually be installed in similar fashion to aluminum windows. Options include nail flange (fin), clips, screw through the frame, receptors, and additional trim accessories such as brickmould and frame expanders; there are plenty of options for any condition.

Shadow boxes

To meet the needs of Passive House and other energy-saving initiatives, exterior solar shading is increasing in popularity. Shadow studies are being widely used not only for impact of the physical obstruction of the building, but also for controlling solar heat gain. Depending on the amount and location of fenestration, reductions in annual cooling energy consumption of five to 15 percent have been reported. Custom extrusion capabilities allow sunshades and shadowboxes to be added to the rough opening and integrated with the window frame.

The detail drawing shows an extruded aluminum shadow box integrated with a window installed above 101.6 mm (4 in.) of mineral wool with a fiberglass support bracket. Since fiberglass is naturally thermally broken, thermal bridging is kept to a minimum.