Pressure-Equalized Glazing System
CSI Division 08, Openings
A curtain wall or window design that deliberately lets a small amount of water past the outer seal into a drainage cavity, equalizes air pressure inside that cavity to match outside pressure, and drains any water back out through weep holes, rather than trying to stop every drop of water at a single outer seal.
Why it matters
A single seal that has to be perfect everywhere, all the time, for decades is an unrealistic design goal. Pressure-equalized design assumes some water will get past the first line of defense and gives it a controlled, intentional way to drain back out, which is a fundamentally more reliable strategy than relying on one perfect barrier. The same drainage principle shows up in masonry as [[concept-masonry-flashing-weeps|Masonry Flashing and Weeps]], applied to an entirely different wall system.
On a real project
A curtain wall system is designed with a drainage cavity behind the outer glazing seal, equalized to outside air pressure through small vents, so that any water that gets past the outer seal drains back out through weep holes at the base of each unit instead of migrating further into the wall.
Who this matters most to
A Glazier installs curtain wall components in a sequence that preserves the system's pressure equalization and drainage path, since blocking a weep hole or drainage cavity during installation defeats the whole design strategy.
Where this goes wrong
An installer accidentally blocks a curtain wall's weep holes with excess sealant while finishing a joint, trapping water that was designed to drain out instead. The trapped water has nowhere to go and eventually finds its way further into the wall assembly than the original seal failure ever would have on its own.