Bold is not an element, but a compound, when it
comes to sustainable design. A LEED Gold-level certified building
is designed and constructed from literally hundreds of integral
components. Moreover, turning bricks and mortar into Gold requires
the combined work of a large team of specialized professionals working
together from the conceptual stage of a project through its completion.
One and Two Potomac Yard in Washington, D.C., is a case in point.
Opened in May 2006, the project earned the Leadership in Energy
and Environmental Design (LEED) Gold level of certification for
new construction or major renovation by the U.S. Green Building
Council (USGBC). The project is one of the largest LEED Gold-certified
office buildings on the east coast.
The Energy Star-rated building is designed to use 20 percent less
energy and 40 percent less water than comparable new buildings.
Buildings are oriented to take maximum advantage of the sun and
expansive views of the Washington, D.C., area. Thermopane-glazed
floor-to-ceiling windows combined with an open-plan interior admits
abundant natural light and affords a direct line of sight to the
exterior for 97 percent of all the spaces in the buildings. Sustainable
mechanical and electrical systems, regional and recycled materials,
and “eco-friendly commuting” amenities—including
parking for 100 bicycles, adjacency to mass transit and 30 electric-vehicle
charging stations—are integral components of the project.
In fact, attention to the environment made One and Two Potomac Yard
a natural fit for the Environmental Protection Agency (EPA), which
leases 405,000 square feet of office space in the two buildings.
Altogether, One and Two Potomac Yard provides 654,000 square feet
of office space.
Situated next to Reagan National Airport and the Virginia Railway,
the project is made up of two adjacent 12-story buildings with sweeping
views of the airport, the Potomac River and the U.S. Capitol. The
two buildings are connected via a green-roofed pedestrian walkway
and provide six levels of parking, with three below grade. Amenities
include ground-floor retail space and a fitness center for the exclusive
use of tenants. The buildings are mirrored in design, projecting
a strong and dignified appearance that is both professional yet
welcoming.
A Sustainable Site
Attaining any one of the five LEED certifications requires excellence
in six categories: Sustainable Sites, Water Efficiency, Energy and
Atmosphere, Materials and Resources, Indoor Environmental Quality,
and Innovation and Design Process.
Ideally, the project begins with a sustainable site. In this case,
the developer, Arlington, Va.-based Crescent Resources, LLC, acquired
the old Richmond, Fredericksburg and Potomac Railroad yard, which
had been declared a Brownfields Redevelopment site due to years
of hazardous contamination from the railway. Following several years
of extensive environmental remediation, construction began on One
and Two Potomac Yard. Originally designed as conventional office
buildings, the developer made the commitment to redesign and build
an environmentally sustainable building. Crescent promotes strong
environmental guidelines for all of its projects.
One and Two Potomac Yard is also designed to meet the emerging needs
of transit-oriented development in this area. The development is
near a Washington Metro station, and a new bus stop was developed
for this project. Additionally, a new rapid transit bus line is
planned.
Architectural firm Davis, Carter, Scott’s knowledge of LEED
design and practices was integral in making the conversion from
a conventional building to a certified one. As architect of record,
Davis Carter Scott worked closely with the design architect, Pickard
Chilton Architects, Inc. of New Haven, Conn., as well as Crescent
Resources to ensure the project would meet LEED and Arlington County
requirements. Like many municipalities, Arlington County is committed
to sustainability and offers incentives to achieve it. In Arlington,
a design that is capable of achieving a LEED Silver certification
may be granted a 0.25-increase in density. Indeed, if a project
is subject to design approval, the county requires that the project
be LEED-certifiable at a minimum. In this case, when the General
Services Administration (GSA) indicated interest in leasing space
for the EPA, Crescent Resources made the commitment to attaining
Silver certification. When the EPA committed to becoming a tenant,
in turn, the developer committed to attaining Gold.
Up-front involvement by all these stakeholders allowed the project
team to balance the needs of the tenant, owner and county. This
is an example of the need for early participation and communication
to bring such a project to fruition.
Daylight, Views and Energy Efficiency
To achieve optimum daylight and views, it is important to orient
the building effectively. At Potomac Yard, Center Park runs north
to south in the midst of all of the buildings, so all buildings
can afford views over the broad expanse of the Potomac River, over
Center Park, or over a wide stretch of the Route One corridor.
Then the design focus shifts to bringing daylight into the building.
There are a couple of strategies normally used on the exterior of
the building, including light shelves, which is a well-accepted
technique that bounces light into the building. However, use of
light shelves tends to require greater ceiling heights, and this
project was subject to strict height limitations. Moreover, Arlington
County’s design guidelines encourage punched windows rather
than a ribbon-window approach. The solution: floor-to-ceiling windows
in combination with an open-plan interior, which admits abundant
natural light and affords a direct line of sight to the exterior
for virtually all of the spaces in the two buildings.
Maximizing penetration of daylight also allowed the use of light
fixtures with daylight sensors, which reduce wattage when natural
light levels permit. In turn, this reduced the amount of energy
required to cool the building year-round. Moreover, precise load
calculations of lighting and office devices were crucial to optimizing
the design of the HVAC system. As a result, in this project the
design team was able to reduce energy use 20 percent compared with
the accepted performance criterion of ASHRAE 90.1 for comparable
new buildings. Designed with energy-efficient mechanical system
components, the system comprises a central chilled-water cooling
system, carbon dioxide monitoring system—contributing to good
indoor air quality (IAQ) by optimizing ventilation—and thermal
comfort system with additional humidity control. Moreover, the mechanical
systems contain no chlorofluorocarbons (CFCs).
In addition to the carbon dioxide monitoring system, use of materials
low in volatile organic compounds (VOCs) is another integral component
to IAQ. In this project, all paints, adhesives, sealants, floor
coverings and composite wood products are composed of low or no
VOC-emitting materials.
From Design through Construction
The use of sustainable new and recycled materials creates a more
sustainable and efficient building, but can be challenging to implement.
The general contractor must be both responsive and responsible in
order for the project team to maximize points in this LEED category.
The general contractor is responsible for a lot of the documentation
that is submitted to the USGBC, and as he procures the materials,
he needs to be sure that what is delivered meets the project team’s
specifications, and then document this in detail. It takes a very
diligent contractor to accomplish this. In this case, the transition
from design to construction was made seamless by the early involvement
of the general contractor, James G. Davis Construction of Rockville,
Md., in the design of the building, which enabled the general contractor’s
team to fully comprehend all of the LEED design issues. The general
contractor’s implementation of an IAQ construction-management
plan also contributed to achievement of points in that category.
Overall, the general contractor was able to fully deliver a high-performance
building without project schedule delay, while minimizing the cost
of sustainable measures for the client.
Sustainable Materials
Use of sustainable materials in the structure, finishes and furnishings
is another key LEED engineering and design strategy, and the building
structure itself can make a significant contribution. In this project,
the post-tensioned concrete structure contains as much fly-ash (a
byproduct of coal combustion at power plants) as possible within
the constraints imposed by air temperature during construction,
and the reinforcement bars contain recycled steel.
With economy and construction efficiency in mind, the architects
designed an exterior finish composed of precast concrete panels
with a cast-in brick exterior. The bases of the buildings are also
composed of a precast base with a granite finish material. Another
benefit of precast concrete is its regional availability; in this
case, the precast plant is located in Virginia. Interior finishes
and furnishings were also specified for sustainability—right
down to the workstations, which feature approximately 40 percent
recycled materials and corn-based fabrics.
Finally, employing LEED-accredited professionals with knowledge
of environmentally sustainable design, materials and construction
methods facilitates certification and earns credit under the Innovation
and Design process category. Crescent Resources; Davis, Carter,
Scott; and Davis Construction employed LEED-accredited professionals
on this project.
Literally hundreds of individual components and the work of a team
of knowledgeable professionals are required to make LEED Gold. One
and Two Potomac Yard is an example for future development, addressing
the issues of growing traffic congestion and pollution in the Washington,
D.C. region. It is also an example of the significant strides that
can be made toward preserving the Earth’s finite resources
when a team with a single-minded commitment to sustainable design
and construction comes together at the early stage of a project.
Douglas Carter, AIA, is a founding principal of Davis, Carter,
Scott Ltd., one of the largest locally owned architectural and interior
architectural firms in the D.C. metropolitan area. He can be reached
at (703) 556-9275. |
