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Breaking the Mold: Variable Vacuum Forming

HouMinn Practice

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University of Minnesota


  • Dave Hultman (Hex mold)
  • Ryan Lodermeier
  • Ashley Eusebio (UBC), Philip Bussey, David Horner, Abigail Merlis, Assoc. AIA, Meggen Skilling (UMN)
  • Blair Satterfield, assistant professor, University of British Columbia (UBC); Marc Swackhamer, associate professor, University of Minnesota (UMN)
  • Renée Cheng, AIA, professor and associate dean of research at UMN College of Design’s School of Architecture for support and advocacy

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Year Completed




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Project Description

Custom fabrication allows architects to overcome what some consider the scourge of repetition in building components. But it also can be wasteful. For instance, variable molding, which is used to make one-off architectural surfaces and finishes, conventionally requires a mold that is discarded after a single use. Blair Satterfield and Marc Swackhamer, principals of HouMinn (pronounced “human”) Practice, located in Minneapolis and Vancouver, British Columbia, set out to streamline the technique, cut costs and waste, and still allow for “endless variation,” Satterfield says. Along the way, something remarkable happened: They eliminated the need for a mold.

Juror Bill Kreysler was enthralled. “It’s huge,” he said. “Forty percent of the cost of making a panel is just creating the shape. Taking that whole issue of cost out of the equation is a big breakthrough.”

HouMinn’s efforts culminated in the VarVac Wall, an ornamental, acoustically absorptive wall installed at the University of Minnesota School of Architecture, where Swackhamer is an associate professor and director of the M.Arch. program. The white plastic panels have an undulating, non-repeating topography of mounds and bubbles, some of which are sliced to expose the underlying green, acoustical fabric.

Each 0.08-inch-thick panel was molded with just heat and gravity. First, HouMinn stretched wires across a plywood frame. Then they took a flat polystyrene sheet, heated it until it was pliable, and laid it across the cables, where it slumped into the voids. The resulting bubbles could be exaggerated with a heat lamp, while the rudimentary cable mold could be modified ad infinitum. “The degree to which it drooped and the shape of the droops was completely open to the placement of wires,” Swackhamer says. To achieve the desired sound reflection or absorption across the panel surface, HouMinn placed the wires based on a Grasshopper script. Droops that exceeded 6 inches were lopped off with a hot wire cutter, creating a hole. “We’re creating a degree of sophistication in the product, but we’re doing it without an extraordinary amount of product, waste, or energy,” says Satterfield, an assistant professor at the University of British Columbia. “As we actively reduce the mold itself, the material becomes more of a voice in the conversation.”

Juror Mimi Love also praised an earlier iteration in the team’s research called Hexwall. Here, Satterfield and Swackhamer built an adaptable vacuum mold using hexagonal aluminum pistons that could be adjusted to produce plastic tiles of varying profiles. The tiles collectively formed a rolling wall surface that could fulfill needs such as reflecting light or accommodating door swing and legroom. “What I particularly like about this submission is the infinite variety of shapes that can be made by a tight grid of hexagons,” Love said.

“For us, as designers, to have a real hand in how production happens, to actually work on making our own tool set, is exciting,” Satterfield affirms. HouMinn moved on from Hexwall because the vacuum mold was expensive to produce and because the process didn’t allow them to “relinquish some control to the whim of the material,” Swackhamer says.

Juror Gerardo Salinas saw larger applications for the firm’s process. “There’s potential to use this technology to wrap a whole building,” he said. Kreysler added, “Forming a material builds into that material’s inherent strength. There’s nothing that says you can’t create catenary arches.” —Gideon Fink Shapiro
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