Building Envelope
Fenestration and Building Envelope Performance
The envelope performs at its weakest continuous line, and that line usually runs around the glazed openings.
Openings concentrate the problem
Opaque wall build-ups can be insulated in depth. Glazed openings cannot, so they dominate heat transfer, air leakage and water management in most envelopes.
They are also where three trades meet, which is why the interface detail matters as much as the system itself.
The four criteria that travel together
Air, water, structural and thermal performance are tested and documented as a set because they interact.
- —Air infiltration affects both energy use and comfort
- —Water penetration depends on the drainage path, not only on sealing
- —Structural performance under wind load changes deflection, which affects sealing
- —Thermal transfer determines condensation risk at the frame and edge of glass
Continuity is the whole point
Insulation, air barrier and drainage plane have to remain continuous across the opening. Where they are interrupted — at anchors, slab edges and spandrel zones — the envelope's real performance is decided.