Secondary Glazing for Bay Windows

Splayed bays (angled returns) are the most common on Victorian terraces and are glazed with mitred corner posts. Square bays project at 90 degrees and are simpler, but the deep returns often need narrower side panels. Curved and bow bays are handled as a faceted series of narrow panels that follows the arc closely enough to be visually seamless.

A bay treated as three independent rectangles leaves a vertical gap at each internal corner. Two gaps running the full height of a bay can represent a larger open area than every other leak in the room combined, and will cap the system at 40-42dB regardless of how good the glass is.

Mitred posts with continuous gasketing close those corners completely, which is the difference between a bay that performs and one that merely looks glazed.

Bays usually contain a radiator, a window seat or both. Frames are set forward of the radiator so convection is not trapped against the glass, and cill-level detailing is designed around seat depth so panels still slide freely.