$6.95
July 2007 Vol. 49 No. 4
Silkscreening
Glass
CONFERENCE
2007 WRAP-UP
Also:
Publications Mail Agreement No.
No. 40005255
Watching Paint Dry
Sound Acoustics for Multi-family Projects
Water Infiltration Woes
www.constructioncanada.net
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Cover Story
Silkscreen Glass
Photo courtesy Christie Spicoluk
Energy performance and esthetics
By Alissa Schmidt, CSI, AIA Allied
F
rom ancient art to current construction, serigraphy (a.k.a.
silkscreen printing) has been an ever-evolving process.
Although estimates of its use date back as early as the 15th
century, the technique was first patented in the early 1900s in
England. Throughout history, various materials and methods
have been explored, but the basic silkscreen printing process
has remained consistent.
To make a silkscreen print on anything from fabric to paper to
glass, the method is basically the same—a mesh fabric is stretched
over a frame. (While silk is the traditional fabric used, a synthetic
material such as nylon is typically chosen for today’s applications.)
Portions of the fabric screen are masked off to create a stencil,
and the screen is placed on top of the material to be printed.
Paint or ink is then pushed across the screen with a squeegee, and
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paint flows through the screen in the unmasked areas to form
the desired image or pattern.
The process of silkscreen printing for use on glass
façades has been available for more than two decades and
follows the same basic process. The paint used is ceramicbased and once applied, must be fired to the glass. Similar
to pottery in a kiln, firing the ceramic frit paint to glass is
done by running the painted glass through a heat-treating
furnace at approximately 593 C (1100 F).1 Once the firing
is complete, the ceramic paint is essentially part of the
glass. Additionally, with the increased knowledge of the
toxic nature of lead, many manufacturers now offer leadfree paint.
There are many benefits of incorporating a silkscreen
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s
Solar control—performance
The traditional method of solar control for glazing typically
involves incorporating an insulating unit with a lowemissivity (low-e) or reflective coating. A coating can reduce
heat gain by approximately 50 percent over a similar unit
without a coating. With sustainable design becoming a
priority, building codes are gradually being modified
worldwide. The reduction provided by a coating is significant,
and in some instances, the glazing may require a higher level
of performance than traditional methods alone can provide.
Adding a silkscreen pattern can help achieve the next level of
performance by blocking more heat than a traditional coated
insulating glass (IG) unit.
For example, the city of Seattle, Wash., requires a maximum
solar heat gain coefficient (SHGC) of 0.40.2 While some
traditional low-e coated IG units can achieve this performance,
many more options are available once a silkscreen pattern is
added. For example, a 25-mm (1 in.) IG unit with a clear low-e
coating has an SHGC of 0.54 and does not meet Seattle’s
requirement of 0.40. Adding a white silkscreen pattern with 50
percent coverage increases performance to an SHGC of 0.37,
therefore, meeting the requirement.
Not only does this increased performance assist in meeting
codes, it can also help qualify a project for the Canada Green
Building Council’s (CaGBC’s) Leadership in Energy and
Environmental Design (LEED) rating system. For instance, under
the Energy and Atmosphere Category (EA), points can be
obtained for reducing design energy cost compared to the energy
cost of the Model National Energy Code for Buildings (MNECB)
or for the American Society of Heating, Refrigerating, and Airconditioning Engineers/Illuminating Engineering Society of
North America (ASHRAE/IESNA) 90.1-1999, Energy Standard
for Buildings Except Low-rise Residential Buildings. Energy
performance above the prerequisite standard reduces the
environmental impact associated with excessive energy use.
Under this category, one to 10 points are available, depending on
how far the standard is exceeded.
Customizing solar control
Although a silkscreen pattern of 50 percent coverage in a
white ceramic frit improves performance, there are several
additional ways to customize the level of solar control to
meet project requirements. One way to adjust the solar
control is to determine the pattern’s optimal placement. The
highest performance is achieved through putting both the
low-e coating and silkscreen on the second surface of the
insulating unit.3 When the coating and silkscreen pattern are
on the same surface, the pattern is applied first, followed by
the coating. While it is possible to place the pattern on the
third surface, this blocks less heat, decreasing the unit’s
performance.
In addition to placing the silkscreen pattern on the second
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Photo © Bob Perzel Photography. Photo courtesy Viracon.
pattern with glass. Designers seeking improved solar
performance, energy savings, reduced glare, and artistic
expression often add silkscreen patterns to the glazing of
building façades.
Esthetics and energy efficiency led to the use of silkscreened
images at the Minneapolis Central Library. Up to 50 different
screens were used to create images on the five-storey building’s
4600 insulating glass panels.
surface, performance can be customized by adjusting the
percentage of glass covered by the pattern. To achieve the
desired esthetic and solar performance, a lower percentage of
coverage may be used with a higher performing low-e coating,
a higher percentage of coverage with a lower performing low-e
coating, or a balance of the two.
The colour of ceramic frit can also affect solar performance.
A medium grey frit, for example, may block more heat than
the traditional white frit. Using the medium grey frit would
require a lower percentage of coverage than a white one to
achieve the same level of performance (Figure 1).
Glare reduction
Architects and designers frequently specify glass with a very
clear, transparent appearance. While this look can be
attractive from the exterior, it can cause glare concerns for
occupants. Glare is any type of light interfering with visual
perception. It can be direct (e.g. the sun or a light bulb) or
reflected from surfaces (e.g. desks or computer screens).
Windows and exterior glazing can be used to reduce glare.
Although the best way to determine the potential for glare is
through project-specific simulation and modeling, a
guideline of 50 percent or more visible light transmittance
(VLT) increases the potential for glare. Depending on the
VLT of a proposed makeup, silkscreening can generally
reduce both transmittance and glare. Since the project may
be driven by esthetics, the percentage of silkscreen coverage
can be customized to meet the proper balance of that goal, as
well as provide solar control and glare control. Generally, the
greater the density of the silkscreen pattern, the greater the
potential for glare control.
Esthetic options abound
Energy performance is just one of the benefits of using silkscreen glass. Once it is determined a silkscreen pattern is
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Photo © Richard Barnes Photography. Photo courtesy Viracon.
Silkscreen is achieved by applying a ceramic-based paint to glass, which is then fired
at approximately 593 C (1100 F). When complete, the ceramic is part of the glass.
advantageous for a specific project,
there are many visual options to be
explored, such as patterns and colour
options.
The basics
Most manufacturers of silkscreened
glazing typically have standard designs,
such as a dot or line pattern. These tend
to provide even coverage over the entire
piece of glass. Typically, standard colours
such as white, black, and various shades of
grey are available. In addition to standard
opaque colours, translucent ceramic frits
can simulate the appearance of sandblasted
or acid-etched glass.
Image courtesy Viracon
Figure 1
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A graduated silkscreen pattern is an
alternate option to the standard patterns.
It starts with a high percentage
(sometimes 100 percent) of coverage
and graduates to a lesser degree, in some
cases fading down to zero.
Beyond the basics—
artistic expression
Using customized patterns, unique
colours, tinted glass, and coatings opens
the door for endless design options, and
a silkscreen pattern can quickly turn a
building façade into a work of art.
Although the majority of manufacturers
have standard paint colours, most also
offer the ability to customize and match
hues. This can be especially beneficial
when complementing glass to other
building façade materials, such as stone or
metal. Colour matching also provides the
opportunity to change a frit shade
throughout the façade even if the pattern
remains consistent.
The design options are even more
numerous when designing a custom
silkscreen pattern. Like creating a stencil,
each area of the artwork must be either
designated as a printed area or a nonprinted area, which is commonly referred
to as black and white artwork. The only
design boundaries are related to the
process itself.
Typically, each element of the artwork
(e.g. dots) must be at least 1.6 mm (1/16
in.) and spaces between the multiple
elements at least 0.7 mm (1/32 in.).
Anything less leaves a very small area in
the screen for the paint to pass through.
This creates the potential for the design to
either not print completely where the dots
are, or filling in where the spaces are
supposed to be.
Is it worth the price?
While silkscreening may add initial upfront costs to the glazing, it can improve
solar performance and by doing so,
reduces a building’s energy consumption, thus saving operating costs
throughout the structure’s life.
For example, consider a building with
457.2 m2 (1500 sf) of 25-mm (1-in.) clear
insulating glass. If a 60 percent white
silkscreen pattern is added to the 25-mm
IG unit, the initial cost is approximately
35 percent higher. The time it would take
to pay back the initial investment,
however, is only four to 12 years.4
Installing a low-e coating and dropping
the coverage to 40 percent further
improves performance and reduces
payback time to three to seven years, even
though the up-front cost to incorporate a
coating is added (Figure 2).
It is important to note a silkscreen
pattern will not decrease in efficiency
over time. Other building products, such
as interior blinds or window films, may
prove to save money after the initial
investment and, thus, have similar
payback timeframes. The difference with
a silkscreen pattern is it requires neither
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Photo courtesy Sota Glazing Inc.
façade is composed of two vision units
(i.e. a lower portion and an upper
transom), it may be possible to silkscreen
the transom, thus saving money on the
blinds. This could also increase occupancy
comfort by reducing the amount of dust
accumulating on the blinds, as well as
lowering the amount of maintenance and
cleaning necessary.
The Toronto Medical Discoveries Tower design team specified a white ceramic frit on
the number two surface of its insulated glass units, and a full coverage grey opacifier
on the number four surface. The elements created a shallow, shadow box effect.
maintenance nor replacement.
The savings and payback timeframes
discussed assume all other aspects of the
building remain as they would have been
without a silkscreen pattern. For some
applications, the addition of a silkscreen
pattern can change other building
decisions.
For example, with improved glazing
performance, it may be possible to reduce
the size of the HVAC system. This would
lower initial costs and the money saved
could be used toward the initial investment
in a silkscreen pattern. Not only can a
smaller HVAC system save money, but it is
also typically the preferred esthetic.
Money is often spent to hide HVAC
equipment located outside a building. A
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smaller system would obviously require
less screening or fencing necessary to
disguise the unit, reducing a portion of
the budget. If applied toward a silkscreen
pattern, both budget reductions would
even further reduce the length of
payback time.
If the energy savings and related
equipment reductions are not enough,
there may be innovative ways to find
money in the budget for a silkscreen
pattern. Could it serve a dual purpose? For
example, if one of the items budgeted for
the project is building signage, it may be
possible to take that portion of the budget
and incorporate signage and logos into
the glass façade. Another area to consider
is interior shading devices. If the glass
Moiré pattern
When a silkscreen pattern is applied to
glass, there is a potential to see a moiré
pattern—an optical phenomenon of
waves, ripples, or circles. Just as the glass
on a building appears different under
sunny versus cloudy conditions, the
moiré pattern may appear or disappear
under changing conditions. It is not a
defect in the glass or silkscreen pattern,
but rather an image formed by the eye.
This moiré is produced when two
regularly spaced patterns—one in front of
the other—are slightly offset, creating
interference. In architectural applications,
this may occur on a glass façade when
silkscreen patterns are used on the second
and third surface of an insulating unit, or
when a second surface pattern creates a
shadow on the third surface.
Special consideration must be given
to the selection of colours, patterns,
and application of these products.
Although there may be cases where
moiré is part of the design intent, it is
undesirable in most cases. While it may
not be possible to identify those cases
where it will occur, the following glass
treatments are generally more prone to
exhibiting a moiré:
• patterns with closely spaced lines,
dots, or holes;
• a silkscreen pattern on the second and
third surface of insulating glass;
• insulating spandrel glass with a
silkscreen pattern on the second surface
and a full coverage frit on the fourth
surface; or
• aluminum panels installed behind glass
with a silkscreen pattern.
Viewing a full-size mock-up is
recommended to better evaluate lighting
conditions at different times of day and
under varying temperature conditions.
The best location to view the mock-up
is at the project site in the conditions
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Image courtesy Viracon
Figure 2
Creating Depth
with Silkscreening
S
ituated on the corner of College and Elizabeth Streets
in downtown Toronto, the new 15-storey Toronto
Medical Discoveries Tower at the Medical and Related
Sciences (MaRS) Centre needed to hold its own in an
architecturally diverse city. (See photo on the cover).
To visually enhance the expansive curtain wall, the
architects accented the glazing system with a controlled
series of silkscreen patterns. Applied in a unique
configuration, the patterns transform the exterior, giving it
added visual interest and depth.
“We manipulated the glass spandrels above and below
the vision panels to make the curtain wall appear to be
composed of predominantly vision glass,” said senior
designer Domenic Virdo at Toronto-based Adamson
Associates Architects, the group responsible for the
building’s design.
“By using a combination of a custom white ceramic frit on
the number two surface and full coverage grey frit on the
number four surface of the insulated glass unit, we were able
to create a shallow, shadow box effect. As light shines through
the frit pattern, a shadow is cast onto the opacified glass
surface giving the cladding a sense of depth.” ✍
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likely anticipated once the project is
complete. Surrounding buildings,
landscaping, or anything else that could
affect the pattern’s appearance should
always be as closely represented as
possible for mock-up viewing.
Innovation and advances
Creative design can sometimes produce
unexpected results and adding a
silkscreen pattern to glass is no
exception. In a project worked on by
this author, a spandrel area was specified
to include a silkscreen pattern on the
IG unit’s second surface and a full
coverage ceramic frit on the fourth
surface. The intent was to brighten the
spandrel so it more closely resembled the vision area and could
help create a continuous façade. The pattern consisted of
19.05-mm (0.75-in.) lines alternating with 12.7-mm (0.5-in.)
spaces. Unrelated to this decision, an interior design selection
was made to install horizontal blinds in the vision areas. On
completion, it was discovered the horizontal lines in the
spandrel areas emulated the horizontal silkscreen pattern. The
blinds, balanced with the silkscreen pattern, helped achieve the
desired continuous look between the vision and spandrel
areas.
A developing area for silkscreened glass relates to bird safety.
Due to glazing’s reflective nature, birds do not always see the
glass façade. As a result, in cities like Toronto, thousands of birds
are killed each year. To help alleviate the number of birds being
killed, some cities, including Toronto, have created ‘lights-out’
strategies for both interior and exterior lighting. The goal is to
reduce reflection from the glass surface, as well as see-through
glass applications often associated with atriums.
Although not as effective as other strategies currently being
researched, silkscreen patterns have been used as a way to
change the reflection on the glass as well as reduce the seethrough, creating a visual marker for birds. When using a
silkscreen pattern for bird safety, the pattern should only be
used in combination with non-reflective glass.5 As further
research is conducted and technology progresses, silkscreening
may become a more viable solution.
Conclusion
Buildings consume a large amount of energy. As awareness and
energy prices continue to increase, the implementation of more
stringent energy codes is being seen in more and more
jurisdictions. Many designers are faced with the challenge of
designing to conserve energy while still providing a creative,
unique building. It can be a difficult task to find products
fulfilling both these needs, especially for the building façade.
Glass with a silkscreen pattern can be used to increase energy
efficiency, as well as to provide endless design opportunities. ✍
Notes
1
Glass is heat-treated in a furnace to increase its strength to
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either heat-strengthened or fully
tempered levels per ASTM C 1048,
Standard Specification for Heat-Treated
Flat Glass—Kind HS, Kind FT-Coated,
and Uncoated Glass. Whenever a
silkscreen pattern is applied, the glass is
heat-treated as part of the process.
2
This is based on the 2004 Washington
State Energy Code plus Seattle
Amendments. See Table 13-1 Building
Envelope Requirements for Climate
Zone 1. For more, visit www.seattle.gov/
DPD/Codes/Energy_Code/
Nonresidential/Chapter_13/default.asp.
3
The surfaces are counted starting with
the exterior as surface ‘number one’
working inward, counting each side.
Each ply of glass has two surfaces; an
insulating unit has four.
4
This is based on the assumptions each
building consists of four façades and
each façade has an equal square footage
of glass. Payback for Washington, D.C.,
New York City, and San Diego, Calif., is
calculated based on November 2006
energy prices for each city as published
by the Energy Information
Administration, Official Energy
Statistics from the U.S. government.
Vancouver and Toronto payback is
calculated based on electricity pricing
of $0.09 per kWh and natural gas
pricing of $0.65 per Therm.
5
See City of Toronto Green Development
Standard (March 2007), Bird-friendly
Development Guidelines, at www.toronto.
ca/lightsout/guidelines.htm.
Alissa Schmidt, CSI, AIA Allied, is an
architectural design associate with
Viracon, an architectural glass fabricator.
She assists design/construction
professionals with selecting practical
solutions that meet project-specific
performance and esthetic needs. In
addition, Schmidt is a member of the
Construction Specifications Institute’s
(CSI’s) Minneapolis-St. Paul Chapter’s
Education Committee. She holds a
bachelor of science in interior design/
construction management from
Minnesota State University in Mankato.
Contents of Construction Canada are copyrighted and are reproduced by FosteReprints with consent of Kenilworth Publishing Inc.
The publisher and Construction Specifications Canada shall not be liable for any of the views expressed by the authors,
nor shall these opinions necessarily reflect those of the publisher and Construction Specifications Canada.
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