How Y2E2 slashes energy and water consumption

Boora Architects Light diagram

Y2E2 is designed to make the most effective use of natural light, distributing it throughout the building in winter and summer, without heating the building. Sun shades are positioned below the top of windows so that there is window above and below the shade. In the summer, when the sun is at a high angle (76 degrees), the sun shade prevents the sunlight from directly entering the building and heating it up. Windows with a southern exposure are shaded from direct sun by an extra-long horizontal sun shade above the top of the window. The north and east windows have vertical sun shades, and the west-facing windows have both horizontal and vertical sun shades. In the winter, when the sun is at a lower angle (29 degrees), it enters the top part of the window and reflects off the top of the sun shade and the interior light shelf. In all seasons, reflected light bounces off the ceiling and through translucent windows on the far side of offices into the interior of the building. The windows on the south side of the building are also slanted slightly up to harvest more light. —Clare Baldwin

The new Jerry Yang and Akiko Yamazaki Environment and Energy Building is projected to use 56 percent less energy and 90 percent less potable water for fixtures than a comparable structure built in a traditional fashion. But how will it eventually reach those goals?

From top to bottom, Y2E2 has an array of sustainable features that fall under five categories: load reduction, passive systems, active systems, energy recovery and on-site generation. These five approaches are expected to slash the building’s power consumption by more than half.

Following is an explanation of each:

Load reduction refers to sustainability features that decrease the building’s dependence on electricity throughout the day, and the biggest energy saver in this category is Y2E2’s leveraging of natural lighting over artificial light.

Four large atriums serve as central light wells that illuminate the common areas on all three floors and in the basement. Office walls rimming the atriums are translucent above 7 feet to allow the light to flow deeper into the building. Also reducing the need for artificial light are light shelves, slabs attached horizontally to the outside of west- and south-facing windows that are painted white on top to catch light and reflect it into the building.

Meanwhile, overhead lighting in the office corridors and conference rooms is automatically dimmed by devices when they sense ample natural light, and motion sensors in rooms turn off lights altogether when no one is inside.

Features of the building’s “skin”—such as the well-insulated walls and roof, as well as the high-performance glass—also are major load reducers.

According to the project’s engineering and design consultants, load reduction is expected to cut Y2E2’s energy use by about 25 percent.

Passive systems are those that rely on the laws of nature to save energy. For instance, the primary method for keeping the building cool and ventilated in hotter months will be a nightly air-flushing process: When evening arrives and the temperature drops to about 60 degrees, top windows of common areas will automatically open to let cool air rush in, and as heat in the building rises it will vacate via the atriums that also will open.

The facility-wide flush will cool the bare concrete floors, which in turn will help the building to feel cooler the next day. Meanwhile, as daytime temperatures rise, the common-area windows—controlled by motors—will automatically close.

In winter, the concrete floors along the western and southern perimeters are designed to absorb and save the heat from incoming sunlight and radiate warmth throughout the day. That is why the common areas are not carpeted.

Individual offices have thermostats and operable windows, and occupants will be able to check the building’s homepage for guidance about when to open and close their windows in order to optimize energy performance.

Tom Bauer, an architect on staff who last worked for BOORA architects—a lead consultant for the Y2E2 project—described how the atriums’ vertical configuration allows “stack effects” to occur when common-area windows open, so when “warm air is rising through the tower, you give it a way to get out at the top. It creates this sort of thermal siphon through the building.”

Passive systems are expected to reduce the building’s energy use by 2 to 4 percent.

Active systems are those that require equipment to induce a result, and one example of this is the active chill beam system installed above south- and west-facing perimeter offices. The beams use a flow of chilled water to remove heat from circulating air. When warm water is pumped through, the beams can heat up a room.

The beams will depend on potable water, but they are more energy efficient than conventional temperature regulation with forced air.

In total, the building’s active systems are expected to yield energy savings of up to 15 percent.

Energy recovery refers to a system that uses exhaust air to either pre-heat or pre-cool incoming outside air. The system uses a coil that retains heat from air exiting the building as exhaust and transfers the warmth to fresh air that the building sucks in; both exhaust air and air being taken in pass over the same coil. The system, which also can cool in-take air by the same process, effectively “takes the edge off” the outside air temperature before using energy to heat or cool it to building set points.

Energy recovery is expected to provide energy savings of about 9 percent.

On-site generation refers to the three different kinds of solar panels mounted to the south-facing roof—including a system that tracks the sun.

Although mainly educational, the panels’ collective output is expected to meet about 2 percent of the building’s total energy usage.

As for potable water, the building will rely on a combination of features to meet its goal of reducing consumption by 90 percent for the fixtures. They include the use of water from Felt Lake to irrigate landscaping, local and native plantings that require minimal watering to begin with and the use of blowdown water from the university’s Central Energy Facility to flush the toilets in Y2E2.

In addition, its bathrooms have dual-flush toilets, urinals that use one-eighth of a gallon per flush, plus a few demonstrational urinals that are waterless altogether. The university also is studying the feasibility of installing a local storm-water capture and storage system that would provide supplemental irrigation for the whole Science and Engineering Quad, thereby reducing the quad’s dependence on the lake water system.

But beyond operational sustainability features, Y2E2 is environmentally friendly in other ways. One example is the use of fly ash, a byproduct of coal burning. It was used as a replacement for cement in the concrete for the basement walls and all the floors, producing 15 tons less carbon dioxide.

The building was constructed with copious amounts of recycled steel, while some finishes made use of rapidly renewable resources—such as substituting bamboo (which grows back quickly and is considered renewable) in places for other types of wood that take longer to grow. Leaving most of the floors uncarpeted saved, literally, tons of raw materials.

The construction of Y2E2 also used much less energy than previous projects: The utility cost for the Clark Center, for instance, was $329,000, while Y2E2 totaled about one-fourth of that at $79,000.

Another feature that makes Y2E2 sustainable is its substantial structural design, particularly in regard to seismic safety. Its seismic design greatly reduces the possibility that the structure will be damaged beyond repair in the event of a major earthquake. In other words, the seismic design is an environmental virtue because its aim is to preserve the building and avoid complete reconstruction.

A rigorous review process, which included peer review by two independent professional engineers as well as input from faculty experts in the School of Engineering and the Department of Civil and Environmental Engineering, produced revisions to the initial design of some key steel brace connections. Those revisions improved the fracture resistance of those connections.

Gregory Deierlein, a professor of civil and environmental engineering and director of the John A. Blume Earthquake Engineering Center, said Y2E2 “employs a lateral force resisting system called an ‘eccentrically braced steel frame,’ which is generally viewed as providing better seismic performance than other structural materials and systems.” This framing system worked well with the building architecture, which features large openings in the floor slabs to create the four atriums, Deierlein said.

According to Richard Luthy, the Silas H. Palmer Professor of Civil Engineering and a senior fellow at the Woods Institute for the Environment, “The secret of a long-lived building is that it can have multiple lives.”