Guide to Glass
A special section of USGlass magazine
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Adhesive Suppliers Guide Architects and
Contract Glaziers in Designing and Installing Structural Glazing
by Ellen Rogers
Designing a structurally sound, aesthetically pleasing façade
is the architect’s mission. Contract glaziers take on the task of installing
the specified glazing system in a manner that ensures sound performance,
while still maintaining eye-catching appeal. This is not always easy.
Tie in the fact that architectural drawings are becoming increasingly
complex and challenging—calling on the glazing systems to perform like
never before—and it’s not hard to see why some may shy away from structural
silicone glazing (SSG), particularly four-sided SSG (see related article
on page 44 in April 2012 USGlass).
Fear not. Many sealant suppliers and manufacturers offer both contract
glaziers and architects and abundance of resources, help and information
that can guide them along the way.
Then and Now
When it comes to structural glazing, much has changed over the past few
decades. Kevin Gerencser, vice president of in-plant glazing solutions
for Tremco Inc., commercial sealants and waterproofing division, says
since his company’s first structural glazing project in 1977, he has seen
the industry mature and become more sophisticated as both knowledge and
confidence have increased with using silicone sealants to adhere glass
“This has resulted in a proliferation of structural glazed systems throughout
the world,” says Gerencser.
In addition, the increased use of specialty coatings on the contact surface
requiring primer, as well as more and more impact and bomb blast requirements,
has also come to the forefront.
According to Doug Walker, vice president of sales and marketing of the
facades, fenestration, insulating glass business unit for Sika Corp. North
America, structural glazing has become one of the most popular methods
of constructing unitized curtainwall.
“Once concerned, conservative suppliers of conventional storefront and
curtainwall systems who were hesitant about offering anything glued in
place now all offer standard two- and four-sided systems that are available
to the general glazing community as opposed to those ‘bold and dangerous’
pioneering days,” says Walker.
Jon Kimberlain, application specialist, high performance building solutions,
with Dow Corning, says one of the biggest changes he’s seen has been the
move from site-glazing to unitized-shop glazing.
“Essentially, the glazing shop has become a factory where many curtainwall
manufacturers now embrace programs such as Six Sigma and lean manufacturing
to make the structural glazing process more productive and cost efficient,”
says Kimberlain. “Two-part sealants that were introduced in the early
1980s appear to play a strong role in the transition as it has sped up
the process of glazing by having a structural sealant that cures significantly
in 24 hours versus one-part sealants that may take more than three or
Andy Shives, Americas marketing manager for Dow Corning, adds that when
properly engineered, fabricated and bench-glazed SSG designs can help
save energy costs to heat and cool buildings.
“The market has seen the proven performance is SSG, which has translated
into more two- and four-sided SSG projects,” says Shives.
Just as design trends change so, too, do products. Manufacturers are following
changing architectural façades and developing, updating and improving
“Other than the change in the early 1980s from an acetoxy-based silicone
to neutral-cure products, and the introduction of a quick-cure, high-modulus
one-part, neutral-cure silicone for on-site four-sided structural work,
bomb-blast and impact-glazing systems, minor changes have been made to
existing products,” says Gerencser. “These [changes] improved handling
characteristics making them easier to use without compromising their proven
He adds one major change, though, was the introduction of a gasket weatherseal
on unitized systems.
“This virtually eliminated the need to ‘swing stage’ the building once
the curtainwall was installed,” he says.
Walker says his company has also modified and updated products. He says
they have developed new products to meet the changing trends of new metal
finishes such as high PVDF-content paints and fast-curing one-part and
two-part cartridge systems for replacement and field installation work.
Shives adds that his company has also continued to update and improve
“We have SSG products for impact resistance and protective glazing,” he
says, explaining that there are products available today that provide
more design freedom with increased movement capability compared to some
of the earlier developments.
While SSG systems have become commonly designed and installed over the
past few decades, both contract glaziers and architects alike still have
concerns. For example, Gerencser, says these often relate to performance
matters, such as the history of the product’s usage in the field; compliance
to ASTM specifications; adhesion and compatibility testing; inspection
and follow up procedures; quality control on site and in the plant; and
“Once the performance issues are addressed architects will focus on the
aesthetics of the products, such as color, while contractors concern themselves
with the delivery system (pump programs) and ease of applications, snap
time and in-plant follow ups by the manufacturer to ensure consistent
quality,” says Gerencser.
Kimberlain adds that these questions can run the full spectrum, depending
on how comfortable each party is with structural glazing.
“We still have architects who are doubtful in the durability of structural
glazing even with the practice approaching 50 years,” he says. “Most discussions
today revolve around sustainability and how structural glazing plays a
role over other choices of glazing by providing a perimeter seal between
the glass and frame to help reduce or eliminate air infiltration ...”
According to Walker, most questions relate to the support they will receive
in terms of testing, recommendations and warranties.
“As structural glazing continues to grow and designs evolve to incorporate
the use of more glass in unique ways, the need for this support has become
even more critical,” says Walker. “A concern has been compatibility between
products and the coordination of trades installing them.”
Lean on Me
As a way to support contract glaziers and architects, many sealant suppliers
offer a variety of resources and support services.
These include AIA-accredited courses for architects, web-based learning
systems, tech-service support, drawing review and assistance, adhesion
and compatibility testing both before the job and during fabrication,
as well as application and testing protocols for both the site and the
“For architects, engineers and consultants we offer ongoing continuing
education programs as well as individualized design and specification
support,” says Walker. “For glaziers we offer product training, laboratory
and field testing and on site assistance as needed.”
According to Kimberlain, his company offers several different educational
“One is the publication of our Americas Technical Manual, which outlines
the recommended practices for successfully glazing with silicone sealants
and a key component in achieving warrantable projects desired by the glazier,
architect and building owner,” he says. “We have been using webinars to
deliver training to our channel partners to ensure proper use and support
of our product. And we are always happy to provide individualized education
seminars to anyone interested in understanding the how’s and why’s of
And manufacturers all agree that testing is essential.
“It is critical with structural glazing systems as you are adhering glass
to the building with a silicone bead,” explains Gerencser.
“Compatibility testing is undertaken at the onset of the job to ensure
the long-term performance of the system is not compromised by products
in contact with each other, negatively affecting each other over time.”
Gerencser also notes that a separate set of tests are required for plural-component
silicones to ensure consistency in mix and product and system performance.
“We conduct plant start-ups including initiating log books and testing
protocols and procedures, which include butterfly tests to ensure uniform
mixing, snap times to confirm cure consistency and, most importantly,
adhesion tests to verify continued performance of the system. The results
are logged daily or as required,” he says.
Walker agrees this is important, as the substrates to which structural
adhesives must adhere or with which they come in contact can change from
project to project and between suppliers.
“Each project should always be tested with the production materials to
be used on the project, not representative or color-approval samples,
such as in the case of paints for metals,” says Walker. “It is also a
useful mechanism to ensure the structural sealant supplier and installer
are talking, reviewing the project together and are in concert with how
the job must proceed.” He notes that for many suppliers there is no charge
for this service.
"Once concerned, conservative
suppliers of conventional storefront and curtainwall systems who were
hesitant about offering anything glued in place now all offer standard
two- and four-sided systems that are available to the general glazing
community as opposed to those ‘bold and dangerous’ pioneering days."
“Product testing is very important to confirm all the materials
coming in contact with the silicone are compatible with each other and
will perform as expected,” agrees Shives. “There is variability in many
substrates so it is important to test for every single project. This is
also required in order to receive a warranty.”
Walker adds, “It’s important for anyone involved with structural glazing
to remember the structural sealant is the most important, strongest link,
which quickly becomes the weakest if not done correctly.”
And, as Kimberlain points out, “It’s a means of validation that the material
will perform as intended, it was designed on paper. Structural sealant
manufacturers offer a 20-year warranty, but the reality is that buildings
are expected to perform much longer so we are really looking at forever-types
of designs. Without the testing, the design only performs on paper until
it is built.”
Looking ahead, adhesives experts expect to see continual evolution in
terms of both design and construction.
“We will see a continuing, increased use of unitized or in-plant wall
systems. This is due to better quality control but, more importantly,
it [helps] reduce construction cycle time, reportedly up to three months,”
says Gerencser. Other changes he expects to see include the development
of sealants that build cure and tensile quicker without compromising adhesion,
which can also further reduce cycle times.
Walker adds that, from a design standpoint, he expects to see not only
the increased use of high-performance glass, but also the use of other
materials—such as concrete, stone and metal combined with glass incorporated
in the facade
“We also foresee more companies incorporating more of the envelope into
their scope of work, more single-source responsibility and [adhesives
suppliers] providing more than just products but product lines consolidated
into systems and methods to achieve the goals that meet or lead the trends.”
Many of the expected future changes also relate to energy-efficiency and
glazing, such as the increasing use of high-performance films in insulating
glass units (IGU), triple-glazed units and electrochromic IGUs.
For example, Gerencser expects to see more dual-wall systems, which can
help improve energy efficiency, while increasing the amount of natural
light that enters a structure.
“Buildings will be commissioned to deliver an energy-efficient environment
where the envelope and internal systems of the structure are balanced
to achieve a sustainable environment,” he says.
Walker adds that the industry will likely need “to coordinate with other
trades to make the proper connections, transitions as well as adopt new
technologies and trades skills, such as those required for solar or electrochromic
Also in the future, expect to see projects that push the design strengths
of the silicone bite in an effort to reduce the amount of metal in mullions.
“Energy and sustainability will be the driver as metal provides high heat
transfer and can impact energy loads,” says Kimberlain. “Decreasing the
metal also will impact the overall bottom line of the total building cost,
as it is a large portion of the building façade.”
But the challenge, he points out, will be how to properly develop the
methods of engineering analysis and testing validation to prove higher
loads are appropriate for designs.
“As I said, we are really looking at the forever business,” he says. “Changing
design stress on a proven technology that has worked for more than 40
years should not be changed with the stroke of a pen.”
Looking at the growth structural glazing has seen these past 30 or 40
years, Gerencser adds, “Structural silicone glazing has had a long history
of outstanding performance based on rigid (but simple) procedures and
guidelines to follow, which should be maintained to ensure continued success.”
Ellen Rogers is the editor of the Architects’ Guide
to Glass & Metal magazine, a USGlass magazine sister publication.
She can be reached at email@example.com
or follow her on Twitter @AGGmagazine and like AGG magazine on Facebook
to receive updates.
© Copyright 2012 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.