Both man and nature have bestowed gifts on Hawaii Preparatory Academy (HPA). With money raised by one of the school’s founders, Geoffrey Clive Davies, Vladimir Ossipoff crafted Davies Memorial Chapel from the massive trunks of indigenous ohia trees, sand, and igneous rock in 1966, and this campus icon is acknowledged as one of the Russian-born architect’s most distinctive buildings. Forty-four years later, Boston-based firm Flansburgh Architects has finished the coeducational school’s Energy Laboratory. Funded by an HPA parent with experience in green energy utilities who challenged HPA to power the building alternatively, the 6,000-square-foot facility is shaped by the trade winds that rush through this corner of Hawaii’s Big Island, is powered by wind and sun, and engages its site in a way that honors the rustic modernism of Ossipoff’s chapel.
According to its director Bill Wiecking, the Energy Lab’s three missions include “education, community outreach, and research,” allowing HPA students to observe different renewable-energy technologies at workfor instance, bifacial photovoltaic (PV) panels as well as PVs with internal invertersand to conduct their own experiments with, say, biofuels derived from native plants. “We hoped by putting this away from other buildings, its tabula rasa quality would open people’s minds to all kinds of field projects,” Wiecking says of the site, which the school had previously used as a dumping ground for construction waste. “Bill also selected the site for fear of dirty wind [wind made turbulent by interaction with trees],” Chris Brown, a Flansburgh associate and the project architect, says of its position above the treeline. The Energy Lab forms the apex in HPA’s triangular campus master plan, and it sits within a small saddle of a south-facing hill that focuses the northeasterly wind that predominantly turns its 5kW vertical-axis wind turbine.
The design is composed of three volumes terracing down the hillside. “This is a bigger building than Ossipoff’s, which are mostly one classroom wide with a lanai,” Flansburgh principal David Croteau says of the multiple academic buildings Ossipoff created for HPA. “By having a building deep in section and sliding the bars by one another, we could create volumes, courtyards, and outdoor classrooms at a scale that made sense with the other buildings on campus.” Moving downhill, the most elevated bar is dedicated to idea generation, the building’s middle has computer stations to facilitate design and run simulations, and the lowest volume is programmed as a workshop. Students then roll their prototypes onto a southernmost porch for testing.
The building was first oriented due south to maximize solar gain, “but it didn’t feel right,” Brown says. Now it faces slightly southeast, in order to not seriously compromise the electricity produced by its 27kW photovoltaic installation. Croteau initially conceived the building’s three parts as curvilinear volumes, and as an “intuitive” response to the trade winds. “It was very different from the design we ended up with,” he says, noting that the realized building hems more closely to HPA’s midcentury architectural vocabulary.
That ultimate design also abides the client’s ambition, determined early on, that the building should be net-zero energy and a strong candidate for LEED Platinum and Living Building Challenge certifications. In this regard, engineering firm Buro Happold, which began collaborating on the Energy Lab project in October 2007, played an important role in determining the building’s shape as well as its orientation.
The designers decided to use the trade winds to their advantage, harnessing the site’s wind for natural ventilation in order to minimize the Energy Lab’s mechanical systems. Matt Herman, who led Buro Happold’s computational simulation team, explains that it began massaging the first scheme with dynamic thermal modeling and airflow network simulations. “One of the challenges the architects brought to us was to provide wind shelter and natural ventilation, so that papers weren’t blowing across desks,” he says. For greater specificity, Buro Happold then applied a computational fluid dynamics model to its efforts, and layered daylight-penetration and heat-gain analyses into its models.
The final shape reconciles Buro Happold’s data with ease of construction. Prevailing winds strike the Galvalume-clad two-pitched roof of the Energy Lab’s uppermost volume, traveling underneath the roofline through horizontally mounted manually operable louvers and up its interior ceiling via laminar flow. Air skirts the top of the facility, so that an internal courtyard is shielded from the buffeting and noise of the constant breeze. The upward movement of the air also creates negative pressure that coaxes stale interior air out of that uppermost volume’s transom windows.
Just as digital tools were vital to sculpting the Energy Lab’s response to the elements, its passive-design strategies are made active by high technology. Wiecking, a physics teacher, created 380 building-integrated sensors and, with a programmer, wrote 35,000 lines of code to actuate building responses to temperature, carbon dioxide, and humidity readings. The transom windows, for example, will open when interior carbon dioxide reaches 1.5 times atmospheric average, while other sensors detecting wind speed adjust the aperture. If the system doesn’t resolve conditions, sensors prompt purge fans, then air conditioners, into action. “I wanted to make sure people feel comfortable in the building in ways that could be automated and invisible, and that the things occupants wanted to control are easily accessible.” All of this delicate choreography is programmed in XML, so that the resulting data can be monitored online at elab.hpa.edu.
Currently Wiecking is conjuring up strategies for the building to predict weather conditions, and to pre-adjust its settings accordingly. Yet not all of the Energy Lab’s helpmates are so invented. Others are adapted, such as the 19 absorber panels installed on the uppermost roof. Normally used to heat swimming pools, here Flansburgh is circulating water from a 2,500-gallon tank through them in the evening to get cool from the wind. By day this naturally chilled water circulates through a radiant cooling system that, Croteau says, “buys us a few degrees of comfort before having to turn on the air conditioning.” With passive and active elements working in tandem, in January commissioners found that the Energy Lab used only 8 percent of the energy generated on site. Several months later the facility was consuming only 30 percent of the site’s production, despite summertime temperatures and the added electrical load of additional computers in the facility.
David Sokol writes about architecture and design from Beacon, N.Y..
Architect, interior designer: Flansburgh Architects, faiarchitects.com
Client, owner: Hawaii Preparatory Academy, hpa.edu
Mechanical engineer: Hakalau Engineering
Structural engineer: Walter Vorfeld & Associates
Electrical engineer: Wallace T. Oki
Civil engineer: Belt Collins Hawaii, beltcollins.com
Surveyor: Pattison Land Surveying
Construction manager: Pa’ahana Enterprises
General contractor: Quality Builders
Consulting engineer: Buro Happold, burohappold.com
MATERIALS AND SOURCES
Appliances: GE Appliances, geappliances.com
Carpet: Bentley Prince Street, bentleyprincestreet.com
Ceilings: Armstrong, armstrong.com
Cladding: James Hardie Building Products, jameshardie.com
Curtain walls: Oldcastle BuildingEnvelope, oldcastlebe.com
Glass: PPG Industries, ppg.com
HVAC: Sanyo, us.sanyo.com/hvac.com
Insulation: BioBased Insulation, biobased.net
Interior walls: Hufcor, hufcor.com
Lighting control systems: Lutron Electronics Co., lutron.com
Lighting: The Lighting Quotient, elliptipar.com
Paints and finishes: Sherwin-Williams, sherwin-williams.com
Photovoltaics: Sanyo, us.sanyo.com/solar
Plumbing and water systems: Solahart, solahart.com
Roofing: Steelscape, steelscape.com; Dura Coat Products, duracoatproducts.com
Signage: Active Safety, activesafety.com
Windows and doors: Pacific Wood Laminates, pacificwoodlaminates.com
Ceramic tile: Sonoma Tilemakers, sonomatilemakers.com
HVAC ductwork: Knauf Insulation, knaufusa.com
Rolling library ladder: Alaco Ladder Co., alacoladder.com
Sliding glass doors: Oceanside Aluminum, oceansidealuminum.com
Jalousie Louvres: Breezway Australia, breezway.com.au