Epiphyte Lab′s Hsu House Mass Wall

Friday, March 25, 2011
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The poured-in-place concrete wall (Susan and Jerry Kaye)

A south-facing heat sink mass wall stores heat and diffuses light, creating an all-seasons solarium for an energy efficient home in Upstate New York.

Dana Cupkova and Kevin Pratt, founders of Ithaca-based design and research practice Epiphyte Lab, met the client for which they built Hsu House in one of Cupkova’s classes at Cornell where she teaches design and fabrication strategies for ecologically adaptive construction systems. The client, a medical doctor, was in the class with the goal of designing his own energy efficient home in Danby, New York, but after an initial consultation, asked Cupkova and Pratt to design it instead.

The wall separates the solarium from the main living space (Susan and Jerry Kaye)

  • Fabricator (mass wall formwork) Epiphyte Lab, SCCM, LLC, and Frank Parish, Cornell University
  • Architect Epiphyte Lab
  • Location Danby, New York
  • Completion Date June 2010
  • Material Cast-in-place concrete
  • Process Numerical simulation, CNC milling, concrete formwork

The 2,200-square-foot house is designed using passive solar principles. Interiors are organized around a three-story living space, which also functions as a ventilation stack. At its center, a south-facing, cast-in-place concrete mass wall creates a heat sink for the house, absorbing heat in warm weather and releasing it when the temperature drops. “It tempers the internal environment of the house,” said Cupkova. “It’s a giant radiator and cooling device. The house has no AC.”

Designing the wall posed several challenges. The team had to create a shape with a large surface area to maximize thermal transfer from the sun to the wall to the home’s interior. But the wall also had to let daylight into the space and, as the sculptural focus of the house, have an interesting shape and texture.

The team began by testing hundreds of parametric iterations of the wall using Grasshopper software, optimizing the design for four-foot-wide concrete formwork components to keep costs down. When Cornell’s CNC mill became unavailable, they turned to Syracuse fabrication company SCCM. Because CNC-milling the high-density polystyrene concrete form liners resulted in a bumpy texture, the team had to rethink its fabrication strategy.

The wall supports part of the upstairs living space (Susan and Jerry Kaye)

“Andy McDonald at SCCM was seminal in helping us figure out the project,” said Cupkova. Frank Parish, Cornell’s digital fabrication shop technician, helped oversee the work. Instead of working with the concrete form liners directly, the shop CNC milled more than 100 guides for the forms, which were then laminated and hand-cut using a hot wire-cutting knife.

Opacity tests (Epiphyte Lab)

Once the forms were in place at the house, the entire structure was reinforced with rebar, allowing it to support part of the floor above. The wall is 23 feet long and 14 feet high with widths varying from 5 1/2 to 16 inches. As Its conical shapes created funnels in the formwork, the concrete mixture had to be adjusted to be more fluid. According to Cupkova, the job is an atypical one for the Ithaca area’s concrete trades, and she credits general contractor Paul Hansen Construction with making the project run smoothly (the fact that she was eight months pregnant also helped her gain some sympathy). As concrete was poured the wall was vibrated, allowing the material to fill the small spaces in the forms. The entire pour was completed in three hours.

Now, the house has weathered two seasons without much use of heating or even electric lights thanks to the mass wall. “In the summer, after it was finished, the temperatures were in the 90s and it was 70 indoors,” said Cupkova. “It works.”

Creating CNC-milled guides for hand-cut form liners (Epiphyte Lab)

Rebar inside the wall provides structural support for the floor above (Epiphyte Lab)

Concrete forms go into place (Epiphyte Lab)

3 Responses to “Epiphyte Lab′s Hsu House Mass Wall”

  1. bruce says:

    Congratulations, that’s a beautiful wall. I’m sure the client is thrilled.

  2. Kiernan Quinn says:

    The forms were successfull. Typically forms like that out of polymer styrene get bubbles at the bottom, so you did a nice job. It appears cold. Without placing heat in the concrete wall, it would seem that is a dream rather than a reality to make a heat sink in Ithaca. That does work in medium climates, but in hot climates with direct sun all day, it fails as well. Do you have any feed-back from the client. gleysteen design tried a similar venture in MA on the North Shore and discovered that no matter how hard he tried to heat the typical vendor spec insulation the building remained cold and the client lived elsewhere. Calculations, calculation, not leed checklists is my comment to Cornell. Also, since the fury of builders are AIA, not NCARB examed, it is my fear that clients will seek other means of building rather than us. As a internet Tycoon told me last month when I tried to win his business, the Architect screwed me in Chicago and I had to mov to North Carolina to get away from my creditor after the building failed. That is common arund here with pen spinning Ivy Leaguers and State Schoolers laden by Frat parties over work. Take the exam and see if that brings the reality to mind. I admit, i learned by doing, but the exam at least peaks your knowledge and then maybe you could use it. Statistics are needed in the beginning to get the difference and understanding between a vendor catalogue cut calc and your need. Well, I would tell you how to get it done, but thats competitive business and Mitre and Bectel already stole some of my jewel designs when the Grand Military called it eminent Domain and paid MIT for a Mndshare download. Billions go out the door on my designs, but nothing to me. So, you are lucky to have a school spnsor you. Thats the nice part of the Ivy. Harvard does not sponsor me, but maybe its a computer failure in crossover like the blue cable or yellow cable thing. Actually color does not matter, its config and labeling: check the label on the cable.

  3. Extraction thimble says:

    Good work!! Thanks!! :)

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