A new dormitory at Unity College in Unity, Maine, constructed by G•O Logic and called TerraHaus, is the first student residence hall in the United States to achieve the European Passive House standard. The building shell reduced the heating load by 90 percent from International Energy Conservation Code–compliant construction, resulting in a near-zero-energy building. Housing 10 students, the compact 2,100-square-foot project is an educational tool for Passive House and sustainable building techniques, and includes monitoring systems that track energy use, thermal comfort, solar hot water production, and air quality.
TerraHaus is the first phase of a redevelopment of one portion of the Unity College campus. The architects oriented the building for southern solar access and used an orchard’s edge at the site’s northern boundary to temper prevailing winter winds. A slab-on-grade foundation system reduced the amount of excavated soils, and preplanned construction staging avoided unnecessary soil compaction and vegetation removal. Disturbed areas were restored with native grasses, trees, and shrubs, creating new native habitats and establishing a web of pedestrian connections to the campus.
Unity’s relatively clear winter skies poised TerraHaus for passive solar strategies. The project’s compact form and super-insulated, airtight construction contributed to a reduction in energy demand for space heating by 90 percent as compared to the International Energy Conservation Code. A mini-split air-source heat pump provides space heating with thermostatically controlled baseboard backup heating in each room. An 88-percent-efficient heat-recovery ventilation system helps lower energy demands. TerraHaus was projected to cost $30 per student per year, which marks a drastic reduction from the $500 per student per year for the residence halls previously on site. Actual performance data for February 2012 showed the building’s energy use at 866 kWh, equating to $13 per student for a winter month. Additional energy reduction stems from 120 evacuated-tube solar collectors that provide approximately 80 percent of the building’s domestic hot water demand.
A mix of low-flow plumbing fixtures including faucets, showerheads, and toilets are used in the kitchen and bathrooms, resulting in an annual usage of 181,000 gallons per year for 10 students. As a residency for students where water demand for showers can be high, a solar-thermal system and two 119-gallon hot-water storage tanks provide domestic hot water.
Materials and IAQ
The foundation system consists of concrete slab cast atop high-density rigid foam insulation to realize an insulation value of R-70. TerraHaus’s wall system achieved an overall R-50 through a combination of structural insulated panels and stud framing with blown-in fiberglass insulation and triple-glazed R-8 windows. Roof areas were insulated with blown cellulose from R-80 to R-100. In the kitchen, inexpensive wooden barn boards add scale and texture, and a cantilevered concrete island offers durability and ease of maintenance. In winter a heat-recovery ventilation system provides tempered outdoor air, while operable windows offer cross-ventilation cooling during summer months.
“Being a design/build firm allowed us to ensure the construction details and concepts were executed precisely, resulting in improved livability, energy performance, and constructability throughout the process. We found many synergies in the Passive House concept. Offsetting savings from reduced energy demands and smaller mechanical systems against an improved building shell and windows results in first-cost efficiencies, and those benefits will increase as energy costs rise over time.” —Matthew O’Malia, AIA, Partner at G•O Logic
“It’s very much a whole project, not just an object from the outside. It’s also really nice to occupy. … Its combination of modern spacemaking and the deployment of the vernacular of that part of the country was quite deft. On the sustainability front, I really enjoyed the modesty of the project. It may hold some nice lessons for housing in the general sense, and not just for student housing.”
Architect, interior designer, construction manager, general contractor: G•O Logic, gologic.us
Client, owner: Unity College, unity.edu
Mechanical engineer: Andrew J McPartland
Structural engineer: Albert Putnam, albertputnam.com
Landscape architect: Ann Kearsley Design, annkearsley.com
Lighting designer: Peter Knuppel Lighting Design
Green Consultant: Svea Tullberg
Adhesives, coatings and sealants: 3M, 3m.com
Appliances: Frigidaire, frigidaire.com; GE Energy Star, geappliances.com
Building management systems and services: Powerwise, powerwisesystems.com
Ceilings: National Gypsum Co., nationalgypsum.com; Viking Lumber, vikinglumber.com
Cladding: Maibec, maibec.com
Flooring: Armstrong, armstrong.com; GO Logic
Glass, doors: Kneer-Sud Fenster, kneer-suedfenster.de
HVAC: Zehnder, zehnderamerica.com; Daikin AC, daikinac.com
Insulation: National Fiber, nationalfiber.com; Branch River Plastics, branchriver.com; Suretight, suretight.com
Masonry, concrete and stone: GO Logic
Millwork: Viking Lumber, vikinglumber.com
Paints and finishes: Sherwin-Williams, sherwin-williams.com
Renewable energy systems (excluding photovolatics): Apricus, apricus.com; Caleffi, caleffi.com
Roofing: Everlast Metals, everlastmetals.com
Structural systems: Mainely Trusses, mainelytrusses.com