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