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


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.”