The Challenge:
For General Marshall Middle School in Austin, designers faced a familiar public-sector paradox: Deliver a landmark educational facility on a tight budget and schedule. For the last project in a $1 billion bond, Austin ISD envisioned a middle school that represented the epitome of their educational goals while reflecting the community’s values and high expectations. Central to these goals were monumental views and connections to the outdoors. The district identified two spaces where this connection should be fostered: the central three-story monumental stair and the long-span dining commons, each facing a central green. But the sustainable standard for that kind of glazing — a curtain wall system — was out of the budget at more than $90 per square foot.
The Solution:
LPA’s design team met early with the structural engineer to talk through options. Storefront windows, a sensible choice when budgets are tight, offers transparency for two-thirds the cost of curtain wall ($60 per square foot), but there are tradeoffs. While a curtain wall has unlimited height, a storefront system is limited to 10 feet. Traditional methods for large expanses of storefront leave large steel members exposed between the panels of glass, lessening the visual impact and dragging down energy performance through thermal bridging.
The interdisciplinary collaboration produced a response that kept the cost down, while achieving the aesthetic the district desired. Instead of aligning the building’s steel structure in plane with the glass, the engineer suggested setting the steel just inside the windows, using thin steel angles to relieve the storefront glazing off the face of the steel. The in-board steel minimized thermal bridging and created a path for sill flashing, which improved drainage and reduced heat transfer while eliminating the visual clutter of exterior exposed framing. In its place, protected from direct sun by the building’s orientation and deep roof overhangs, the glazing delivered the look and performance of a curtain wall at the promised discounted cost.
“There’s an element of pride to these spaces — so tall and full of light, looking out to the heart of campus,” Federico Cavazos says. “We wanted the students to feel special. It’s about equity and dignity and sending a message that you matter.”
