From Zero to Net-Zero Squared

Jan. 1, 2008

Zero is hero at the Integrated Design Associates facility in San Jose, CA.

By Christine Lewers

Scott Shell remembers the day he showed his staff pictures of a 1960's-era San Jose, CA, building his firm was hired to remodel. The vacant building, a former bank branch of precast tilt-up construction, was windowless, partly covered in fake stone, and sat forlornly amid a sea of parking lot.

"They burst out laughing, and then they realized, ‘Oh, my gosh. We really have to do something with this,'" says Shell of EHDD Architecture in San Francisco.

Then they got to work, and they proved that sometimes it's the smaller projects and most unassuming buildings that can take the biggest steps forward in sustainable design. Today, the 7,200-square-foot building is a net-zero-energy, zero-carbon-emissions (or Z squared) commercial space, meaning the facility generates as much energy as it uses and does not burn fossil fuel. Instead, photovoltaics supply 100 percent of the building's energy needs.

The building is the new headquarters of electrical engineering and lighting design firm Integrated Design Associates (IDeAs). From the outset, owner David Kaneda knew he wanted the office to showcase the latest in high-efficiency lighting technologies both to attract green-minded clients and to provide a working laboratory for the electrical engineers and lighting designers who work there.

But going net zero energy, zero carbon emissions took a leap of faith, admits Kaneda. His impulse during planning 2 years ago was to try for a LEED Platinum building, which would require meeting a long checklist of requirements in areas ranging from material use to water efficiency. He says Shell turned him onto the idea that focusing resources on an all-electric building made more sense for an electrical engineering firm.

"Now it seems like it was an easy decision to make, but this was before ‘An Inconvenient Truth' and before global warming was all over the headlines," says Kaneda. "To me, it felt like we took a sharp left. Now it seems like the rest of the world is taking a sharp left also."

Above Left: Before, Above Right: After
Designers transformed a forgotten bank branch made of 1960s-era precast tilt-up construction into a zero-net-energy, zero-carbon-emissions commercial space.

Built-in energy efficiency was paramount to the project's success. The building's roof holds a finite number, only 76, of power-generating photovoltaic modules. A tightly integrated team of architects and mechanical and electrical engineers worked to wring as much energy efficiency out of the building as possible by tackling HVAC, lighting, and plug loads.

The team reaped huge savings by designing a ground source water-to-water heat pump system to provide both radiant floor heating and cooling. They let daylight in to virtually eliminate the need for electric lighting during the day. Finally, they fitted the office's lights and equipment with a variety of controls designed to save energy and allow IDeAs' engineers to compare performances.

All told, Kaneda estimates the building will use about 56,000 kilowatt hours per year, about 60 percent less than a typical office building its size. The remodel cost about $1.8 million, which reflects both the high cost of Bay Area construction and the expense of newer photovoltaic and glazing technologies, some of which are beginning to come down in cost as demand increases, says Kaneda. He expects to recoup up-front costs of the photovoltaic system in about 5 years.

Cool Floor/Cool Roof
The design team knew Kaneda's investment in a Z-squared building wouldn't pay off if the people who worked inside it were uncomfortable.  "There's sometimes a misperception that energy efficiency means sacrificing comfort," says project team member Peter Rumsey of mechanical engineering firm Rumsey Engineers in Oakland, CA. "We tried to deliver better-than-average comfort and lower energy use."

The solution, he says, rested on separating the building's heating and cooling functions from its ventilation system. Without forcing air throughout the building for heating and cooling, the ventilation system is smaller and more energy efficient. Cooling and heating the slab, rather than all of the air in the building, also cuts energy use.

Workers installed a crosslinked counter flow PEX radiant tubing system in the slab to both heat and cool the floor.

In addition, the ground would do a lot of the work. Workers dug up a 10,000-square-foot portion of parking lot east of the building to bury a horizontal grid of polyethylene (PEX) piping at depths of both 4 and 6 feet, where ground temperatures are constant at 57 degrees. A 10-ton geothermal ClimateMaster heat pump uses this constant temperature to chill or warm water that is then supplied to two Taco pumps. The pumps push the water through a cross-linked counter-flow PEX radiant tubing system within the slab to heat or cool the floor.

While radiant slab heating has a reputation for delivering comfort, radiant slab cooling is less tested in this country, says Rumsey. In-slab radiant cooling works because occupants' body heat radiates to a cool floor so they feel comfortable even when air temperatures surrounding them are higher than in a traditionally air-conditioned space. The effect is like the cooling you feel when, on a hot day, you enter a European cathedral with a thick marble floor, he says. Kaneda reports that, even with the thermostat reading 78 degrees, the 65-degree slab keeps workers cool at an energy savings of about 60 percent.

A cool floor, however, can condense atmospheric moisture, says Johnson Controls Project Manager Ken Martin, whose team designed and installed the radiant controls system. To prevent any possibility of condensation, workers put sensors on the slab that provide information to a Johnson Controls Metasys building management system, which compares the floor temperature to the room's air dew-point temperature. When office air is too humid, dehumidification kicks on. 

Using the slab for heating and cooling also cuts the amount of air the ventilation system has to blow through the building to about 25 percent of a typically air-conditioned space, says Rumsey. This, too, saves energy, while smaller ducts and fans save space. It also means that the building's dual coil Trane air handler is free to deliver 100-percent outside air, conditioned to a constant temperature by the heat pump, into the building.

A lightweight building integrated photovoltaic system (BIPV) supplies all the building's energy needs, eliminating the need for fossil fuel.

Supplying energy to run the mechanicals is an all-in-one roof and power supply system, or building integrated photovoltaic system (BIPV). Here, the team specified a Solarsave roofing membrane manufactured by Open Energy Corp. and made up of fire-rated, single-ply white PVC with built-in SunPower A300 monocrystaline solar cells. Because it's white, the surface of the roof absorbs less heat. At about 2 pounds per square foot, the system is also very lightweight. No extra structural support was needed, another plus for the design team.

Let the Sun Shine In
Shell knew a smart daylighting plan would save energy by cutting back on the need for artificial light during the day. On the other hand, lighting the space naturally had the potential to raise temperatures inside the building, overtaxing the building's cooling system. In addition, skylights would take up valuable roof space needed for photovoltaics. The right daylighting strategy was a balancing act.

In this respect, the building was obliging, says Shell. About half of it, 3,100 square feet, is one-story, open-studio space. The other half is two stories comprising 4,100 square feet, which Kaneda intended to lease. This arrangement gives the building lots of roof space in relationship to square footage, potentially enough space for photovoltaics to supply 100-percent power.

Skylights bathe the office's north wall in sunlight, which is reflected back into the studio space.

In addition, 18-foot ceilings in the studio space worked well for diffusing light coming in through skylights to workers below. EHDD and IDeAs collaborated to design a centrally located, 3x3 grid of 2-foot-square skylights using PPG Solarban 70XL, a spectrally selective glazing with the highest visible light-to-solar-gain ratio available (2.33) to allow visible light in but keep ultraviolet light out. They also positioned a narrow row of skylights along the north wall, bathing it in sunlight that is then reflected back into the studio space. High-reflectance paint on the walls helps spread the natural light.

To the south, a section of sliding glass doors serves as the office's main entryway. Shading the doors from a direct hit of the sun is an Open Energy Solarsave laminated integrated photovoltaic system. The overhang not only supplements the roof's power system, but it's also a design element. "You can look up and see the cells," says Shell. "And there are little spaces between them, so you get a filtered light, sort of like sunlight coming through tree branches."

Except for windows on the east side of the building, all windows are made of Solarban 70XL. To the east, electrochromic glazing and SAGE Electrochromics darkens a 4- by 14-foot section of windows to reduce glare in the morning, much like photogray sunglasses. A photocell on the outside of the building senses direct sun and signals for an electric current to pass through the glass to tint it. The windows lighten again once the sun rises overhead.

Lightening the Load
Even if there is no need to artificially light the space during the day, the building has a range of lights, sensors, and controls, all of them high efficiency, allowing for side-by-side research and comparison, says Kaneda.

For example, three pairs of Finelite high-efficiency linear fluorescent lamp fixtures hang from the studio's ceiling. Two are fitted with Watt Stopper/Legrand daylight harvesting sensors and one is controlled by a Lutron Ecosystem. One is controlled to switch on/off, while the others have dimmable ballasts.

Another goal Kaneda had for the building was keeping plug loads as low as possible. Workstations are equipped with LCD flat-screen monitors, which use about half the energy of CRT screens. Beneath work areas are Watt Stopper plug strips with occupancy sensors that shut off power to monitors, stereos, and task lights when workers leave their desks. The office's printers are tied to the building's security system so that when it is armed, a signal automatically shuts down the printers' dedicated circuit, ensuring the machines are not left in standby mode all night.

The building is also responsive to workers, says Mark Fisher, IDeAs principal. Most staff use wireless telephones. A Wi-Fi data system lets staff move throughout the office or outside, where an enclosed entry courtyard serves as a break or meeting space. "It's not just sustainable, it's a comfortable place to work," says Fisher.

Outside, designers stripped the building of all ornamentation and painted it clean shades of grays and blues. It remains an unassuming building, but its back-to-the-basics look says it all. Skylights, tinted windows, landscaping, and a patterned overhang are the building's primary design elements. They also represent the architectural tools that can work with technology to halve the energy consumption.

"Daylighting, orientation, really paying attention to those fundamentals and not just paying lip service to them" can make all the difference to the world's energy problems, says Shell. "We like to use it for inspiration for design." 

Christine Lewers ([email protected]) is a freelance writer based in Iowa City, IA.

Product List

Heat pump: ClimateMaster
Water circulation pump: Taco Inc.
Metasys controls: Johnson Controls Inc.
Dual coil air handler: Trane
Electrochromic glass panes: SAGE Electrochromics Inc.
Spectrally sensitive glass: Solarban® 70XL Solar Control
Low-E glass: PPG Industries
Lighting fixtures: Ledalite, Finelite, Litecontrol, Alkco, Prescolite, Zumtobel,
Elliptipar, Metalux, Strand, Surelite, Isolite, AAL, Shaper, Invue
Lighting controls: Watt Stopper/Legrand, Lutron, Square D
Data rack; cable tray: Chatsworth
Telecom equipment: Leviton
Cat 6a cable; patch cords: Superior Essex
Power control and metering: Square D
Inverter: Xantrex Technology
Photovoltaic system: Open Energy Corp.
Roofing membrane; PV glass: SolarSaveTM Architectural
Solar cells: SunPower A300
Floor boxes; walker duct: Wiremold
Line-voltage wiring devices: Pass & Seymor
Sensor-controlled faucets: Sloan
Dual-flush toilet: SmartFlush by Caroma

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