Double-Skin Façade Designs on
the Rise in North America
by Jeffrey Vaglio and Mic Patterson
We’ve heard about them, some of us have seen them, fewer
of us have actually worked with them, but that may be about to change.
In spite of the adverse economic conditions, double-skin façade
(DSF) applications have actually increased; they’re part of the green
trend that continues to thrive in the down economy. So what are they,
what’s the point and can you expect to see one in your backyard anytime
soon? Well, it depends a little on where you live, but with recent applications
in major metropolitan areas including New York, Boston, Chicago and Los
Angeles, the chances are that there may be one not too far from your doorstep.
DSFs are simply a strategy for improving building envelope performance
through the introduction of a second glazed layer, thereby creating an
airflow cavity between the two.
The application of the technology in the United States has been a long
time coming. Although early examples of DSFs exist here—the Occidental
Chemical Center in Niagara Falls, N.Y., in 1980 is but one example—the
major development and implementation of the technology took place in Northern
Europe through the 1990s and 2000s. Numerous completed examples of a great
variety of DSFs were driven by legislative mandates for improved energy
efficiency in buildings. The impetus for the initial development of DSFs
was not only thermal comfort and energy efficiency; it was also about
acoustical performance, as these façades mitigate sound transmission
through the glazed building envelope. This is still a very good reason
for their use, especially as our dense urban environments become increasingly
populated with residential dwellings. Nonetheless, thermal performance
and natural ventilation have been the more recent drivers of this advanced
It’s All About the Cavity
Let us provide some background on DSFs. The cavity is useful for a few
things. First, it acts as a thermal and acoustical buffer between the
inside and outside environments. Second, the cavity can be employed in
various ways to provide airflow and even building ventilation. Third,
the cavity provides an optimal space for the location of shading devices:
outside the inboard skin so that solar radiation is stopped before penetrating
into the building, yet shielded from the elements by the outboard skin.
If the cavity is deep enough, it can also house mechanical equipment and
maintenance platforms. Cavity depth ranges widely—from about 4 inches
to 6 feet—among the various built DSFs. It should be no surprise then,
that the applications of DSFs are most often categorized by variations
in cavity design and behavior. Specifically, ventilation type, ventilation
mode and cavity partitioning are the most commonly used criteria.
The ventilation type refers to the driver of airflow within the cavity,
which can include natural, mechanical and hybrid systems. The ventilation
mode refers to the airflow pathway from intake to exhaust. The five common
ventilation modes are outdoor air curtain, indoor air curtain, air supply,
air exhaust and buffer zone. The diagrams in Figure 2 trace the pathways
characteristic of each mode. Finally, DSFs are most usefully classified
by the cavity partitioning strategy employed in any given design. The
four primary cavity configurations are box window, shaft-box, story-height
(corridor) and multi-story (see Figure 3). Each configuration possesses
unique attributes of design, performance and application. The multi-story
types tend to be the deep cavity systems, while the other configurations
typically utilize much shallower cavities.
Trends in DSF Applications
In a recent evaluation of 23 existing applications, the most common DSF
cavity partition configuration in the United States is the multi-story
(70 percent) and the most common ventilation mode is the outdoor air curtain
(74 percent). The multi-story DSF cavity has no horizontal or vertical
divisions, and may encompass an entire elevation of a building façade.
Intake air openings are placed at the bottom of the cavity, with exhaust
openings at the top. Ventilation of the cavity can be induced naturally
through the stack effect (as the cavity air warms it rises and is exhausted
through the top vent, in turn drawing air into the cavity through the
bottom vent) or mechanically assisted as required to prevent overheating
of the cavity air. The more advanced designs utilize this cavity behavior
to provide ventilation to the building. The Richard J. Klarcheck Information
Commons at Loyola University in Chicago (see Figure 4) utilizes this effect
in a west elevation DSF. In this application the stack effect is augmented
by offshore winds that act to draw air from the cavity at the top vent.
Multi-story DSFs can provide a unique, highly transparent aesthetic, abundant
daylight, a thermal buffer, enhanced acoustical performance and can contribute
to building ventilation. Potential disadvantages include flanking sound
and odor transmission through the cavity, overheating of the cavity air
if ventilation is inadequate and building code issues with respect to
fire-safety because of the lack of fire-safing between floors. Design
flexibility is greater with the multi-story DSF types than with any other
category. Many variations are conceivable, and this DSF type has been
applied on educational, museum and healthcare facilities, among other
The evolution of DSFs in the United States exhibits other emerging trends.
An alternative to the multi-story system is the increasingly popular box-window
type, with a cavity depth at the shallow end of the spectrum, typically
in the range of 4 to 8 inches. This DSF type is configured as a modular,
prefabricated, unitized curtainwall system appropriate for high-rise buildings.
The location of mechanized systems, such as shading products, within the
cavity of the DSF means that the cavity must be accessible for maintenance
purposes, significantly complicating the design of a unitized façade
system. The lack of a hermetic seal in the unit means that airborne particles
and moist air potentially can infiltrate the cavity, resulting in dirt
and condensation on the inner glass surfaces and further escalating the
maintenance requirements. Current development efforts are aimed at addressing
these issues. In addition to high-performance unitized curtainwall systems
capable of cladding an entire building, box-window configurations can
be developed as discrete window or window wall units, and have been used
as a façade component in office, residential and hospital projects
where the floor plan is subdivided into many repeating units (offices,
condos or patient rooms).
AJ Celebrezze Federal Building to be
Re-Clad Using Double-Skin Technology
by Ellen Rogers
The AJ Celebrezze Federal Building in Cleveland,
built in the mid-1960s, is undergoing a transformation that includes
a double-skin technology designed to create a more energy-efficient
structure. Interactive Design Inc. (IDEA), led by partner Charles
Young, was chosen as the project architect. IDEA’s design plans
will utilize a glass double-wall technology it says has never
before been used on a high-rise in the United States, though common
in Europe. The technology is designed to upgrade the perimeter
structure to improve the costs of operating the building and minimize
temperature variances throughout the edifice utilizing advanced
systems available for cladding. The project is funded through
the American Recovery and Reinvestment Act (ARRA).
“In the planning phase, it became obvious to us that the design
needed to utilize solar orientation to drive the architectural
concept, as seven months out of the year Cleveland experiences
relatively cool to cold temperatures,” says Young. “We determined
that the Celebrezze building was an ideal candidate for double-wall
technology, a sustainable green and advanced technology system,
which utilizes double glass lites to insulate the building and
maintain visual purity.”
According to architects, a new external curtainwall will be placed
approximately 2 ½ feet beyond the face of the original
building skin. In this way, the existing façades can be
retained and used as the internal portion of the double wall resulting
in a thermal blanket similar in concept to a thermos bottle. This
approach helps ensure minimal disruption to the existing tenants
in the building by utilizing the existing façade to serve
as a protective barrier between the façade construction
process and building employees.
In designing the structure the IDEA team looked at how the building
responded to the sun’s light. Downtown Cleveland is planned on
a grid, similar to other major cities, such as Chicago, and in
both cities the grid runs parallel and perpendicular to the lakefront.
While the Chicago lakeshore runs more or less south to north,
the Cleveland lakeshore runs southwest to northeast roughly 35
degrees off latitude. As a result, the building receives sun exposure
on all four façades throughout the year.
In response to this solar orientation, the design addresses north
and south facing façades differently. The east and north
façades receive mostly oblique angled light in early morning
and late afternoon. The façades for these two sides are
transparent with perpendicular interior fritted glass fins that
filter and modulate this oblique light. Glass edges are detailed
to float over the existing building to highlight the new high-performance
skin and the original façade structural frame.
The south and western façades receive direct midday solar
exposure. These façades have been developed with a double-wall
construction to provide an insulating envelope in winter months
and to reduce heat within a barrier zone in summer months. Horizontal
light shades are utilized within the cavity to reduce direct sunlight
on the interior tenant space. Glass is treated with a graduated
frit pattern from almost opaque to clear from top to bottom to
further reduce direct glare and heat loads on the building systems
and improve tenant comfort.
Arguably, the most compelling future application of DSF technology is
in building retrofits (see sidebar on page 10). Realizing energy consumption
and carbon emission reduction goals established by various green platforms,
such as the White House Agenda and the 2030 Challenge initiative, will
require energy retrofits to a large percentage of the current building
stock, many of these programs should include façade retrofits.
Many of the early glass curtainwall towers built during the 1960s and
1970s were constructed originally as single-glazed façades with
low visible light transmittance glass; they were poor energy performers
from the beginning and now are approaching something very close to old
age. The addition of a second skin may prove to be a viable approach in
some, if not many, of these buildings, providing greater economy, modernizing
the appearance and improving energy performance.
DSFs are one strategy of an emerging advanced façade technology
that includes new glazing materials, improved framing systems, progressive
techniques and novel designs. That unique attribute of glass assures it
will remain a predominant material in the building skin.
Glass, however, as we well know, is a poor thermal and acoustical insulator,
and these negative attributes threaten to limit its use in this same context.
It is imperative that we, as an industry, do not adopt a defensive position
in an attempt to protect a vested interest. We must embrace the mandate
for improved energy efficiency and reduced carbon emissions in buildings,
and deliver solutions that optimize façade performance and nullify
these negative attributes of glass. This will assure the benefits provided
by the unrestricted, but appropriate use of glass in the building envelope.
The ultimate viability of DSF technology, and the role it will play in
future building façades, is unclear. We need to make a more aggressive
and sustained effort in the attempt to better understand how these very
interesting experiments in advanced façade design are actually
performing. The needed solutions will involve an intensifying collaboration
between the profession, academia, and industry, and will require ongoing
investment in research and development by all stakeholders.
Jeffrey Vaglio and Mic Patterson are both
PhD candidates in the School of Architecture at the University of Southern
California. They are employed by Enclos, the national curtainwall firm
headquartered in Eagan, Minn., and work out of the firm’s Advanced Technology
Studio in Los Angeles.
Architects' Guide to Glass
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No reproduction of any type without expressed written permission.