Which glazing tape is right for your glazing application? There are two primary questions to address when determining what type of glazing tape should be used in fenestration applications:
Do you have a glazing detail?
The glazing detail is an engineering drawing showing the glazing method required. It specifies the components needed including glazing tape type, setting blocks sizes, liquid sealants, etc. It is provided by product engineering in the case of window, skylight and door fabrication. In curtain/window wall, or storefront commercial glazing, architects or project engineers provide the glazing detail. In rare cases where it is not provided, the fabricator will need to determine the best type of tape to use.
Specifiers may call out a particular type of tape (example, “silicone structural glazing tape,” etc.), or they may say “X brand of tape, or equivalent.” Some drawings will simply refer to glazing tape, in which case the individual responsible for specifying the correct glazing tape will need to understand the different glazing methods and the optimum tape to use in each one, based on the fenestration product design.
What type of glazing are you doing?
The glazing technique is critical because it determines the type of tape to use in any fenestration system. When this is given, you may use our glazing tapes cross-reference chart to determine the equivalent product to the tape specified.
Glazing tape methods tend to fall into three basic categories:
Drop-in glazing, used in residential windows and doors. It is applied in almost all vinyl window fabrication, most aluminum windows and some wood window fabrication. The Insulated Glass Unit (IGU) is dropped in to a 4-sided glazing pocket, with a pressure cap, or bead applied to hold the glass in place after glazing. Drop-in glazing is the most common type of tape glazing method and it’s called out by product engineering. It is very quick to fabricate and provides an excellent seal.
Structural glazing, used in skylights, commercial windows and doors, and curtain wall. While many designs call for silicone caulk in structural glazing, this technique involves using an acrylic foam tape in lieu of the silicone caulk. This is also called dry glazing. Structural glazing is specified by an architect, specifier or project engineer. The major advantages of using structural glazing tapes are clean sight lines, very rapid cure times and ease of fabrication. Units can be moved immediately after glazing, saving valuable shop space and time.
Silicone structural glazing, used in commercial windows, doors and curtain wall and cladding. The glazing tape is applied to the frame, acting as a spacer tape, giving a uniform gap between the frame and the IGU, which is then filled in with a liquid sealant (typically a silicone caulk). Silicone structural glazing is specified by the architect or specifier/engineer. This glazing system assures maximum bond strength and the insurance of a secondary seal, which also gives maximum service life.
Drop-In Glazing For Residential and Commercial Windows and Doors
In the drop-In glazing method, the IGU is dropped into the glazing pocket after the tape. Often times, setting blocks are pre-applied to the glazing pocket. The final step is applying the snap-in, or screw in pressure cap, which ideally should provide approximately 25% compression on the glazing tape. This technique can also be used with a secondary seal, such as a bead of silicone caulk, along with the glazing tape to provide a secondary seal and even greater strength to the glazing.
Drop-in glazing requires tight tolerances on the IGU because it needs to fit very closely within the glazing pocket. The glazing detail will provide the exact size(s) of the IGU, the setting blocks, the glazing tape and any additional materials.
The tapes that are utilized in this type of glazing are BGT crosslinked polyethylene glazing tape, 15# and 25# PVC glazing tapes.
BGT Crosslinked Polyethylene Glazing Tapes
Often used as a primary sealant, BGT crosslinked polyethylene glazing tapes are designed to provide the final seal between the sash frame and the IGU in drop-in glazing. BGT is applied to all four sides of the glazing pocket, with a butt joint at each corner, best practice is to put a very thin bead of compatible sealant at each joint.
While BGT will provide the primary seal, it is fully compatible with most neutral cure and two-part silicone sealants, so the tape can be used with a heel, toe or cap bead of silicone, if needed. This technique provides the advantage of a primary and a secondary seal, and great structural integrity. There is no need for curing or edge trimming when using this tape, and glazing with this tape will create very clean sight lines, a requirement for many high end window and door systems.
BGT is a closed cell foam tape, with AAMA approved high performance, solvent based acrylic PSA coated on both sides, and a blue 5 mil HDPE release liner (PP liner is optional). The closed cell foam prevents water absorption and penetration through the tape. The acrylic adhesive system gives a very wide service temperature range, both high and low and is very weather resistant. BGT is available in black and white in 1/32", 1/16" and 1/8" thick.
BGT is made self-wound, meaning the blue HDPE (or PP) release liner is on the outside of the roll, when the roll is unwound it exposes the adhesive on the opposite side from the release liner, allowing the user to easily apply the tape to the glazing pocket.
There is a simple trick of the trade used in instances when the insulated glass unit (IGU) is dropped in and may be slightly out of place. This is very useful in cases where the setting blocks are put into place after the IGU.
Approximately 1” of the tear resistant HDPE liner (or PP) is pulled back, exposing that much adhesive, then the liner is bent at a 90 degree angle, so that tab will be left exposed after the IGU is dropped in place.
With this small amount of adhesive exposed, the IGU can then be repositioned.
Once the IGU is in the correct position, the tab can then be pulled from the inside of the window to remove the rest of the release liner and expose the adhesive on all of the tape prior to applying the glazing bead, or pressure cap, which is the final step in the glazing process.
PVC Glazing Tapes
15# & 25# PVC glazing tapes from Gaska Tape are used as the primary seal in drop-in glazing between the sash frame and the IGU. These tapes are specified when a higher density tape is required and where there is concern with expansion and contraction of the tape. A big advantage of PVC is the very low compression set, meaning that it will recover very well after periods of compression (ex. extremely hot climates, which cool off at night).
PVC glazing tapes are also fully compatible with neutral cure and two-part silicone sealants. This allows them to be used with a heel, toe or cap bead of silicone, when required. PVC tapes do not require curing or edge trimming which enables very clean sight lines, a design feature required in high end fenestration projects.
These tapes are made of closed cell, high density PVC foam, with a high performance, aqueous based acrylic PSA coated on both sides, and a brown kraft paper release liner. An optional blue HDPE release liner is also available. The aqueous A3 acrylic adhesive system provides excellent quick stick.
PVC glazing tapes are made self-wound, meaning the liner is on the outside of the roll. When the roll is unwound, it exposes the adhesive on the opposite side from the release liner. 15# PVC is available in black in 1/16”, 1/8”, 3/16”, 1/4", 3/8”, and 1/2” thick. 25# PVC is available in black in 1/32” thick.
PVC glazing tapes provide good sound deadening/vibration damping qualities, and a long life seal against water, air and dust penetration. These tapes are resistant to most chemicals, acids, solvents, UV, fungi and oxidation. They are also weather and fire resistant. A special formulation is available with UL-94 HF flame retardant rating, on a special order basis. The 15# PVC Glazing Tape is AAMA approved.
Structural Glazing for Curtain Wall and Cladding, Commercial Windows and Doors
In structural glazing, the glazing tape is used to hold the IGU in place, provide a primary seal and structural strength. The tape provides very high shear, tensile and elongation strength, which are critical structural elements of the final fenestration system. The structural glazing tape must withstand all of the various forces to which the finished fenestration product will be exposed including hurricane force winds, wind shear with dramatic drops in pressure, etc.
Structural glazing tapes provide clean sight lines. The edge of the tape can be aligned exactly with the IGU spacer and the structural frame, also referred to as zero sight line glazing.
The structural glazing tape has excellent quick stick, meaning it provides immediate bond strength, so the unitized frame, door, skylight or window can be moved right after glazing without the concern of components shifting during transit. On the other hand, silicone caulks require cure time after application prior to moving the glazed product. This is a real time and space saver when glazing large unitized frames, which can be packaged and sent out to the field as soon as they are glazed.
Acrylic foam tapes are ideally suited for structural glazing due to their high tensile and shear strength. Their viscoelastic properties allow the tape to recover after periods of extreme stress.
SGB, SGG and SGW Acrylic Foam Structural Glazing Tapes
SGB (black), SGG (gray) and SGW (white) structural glazing tapes by AFTC are double coated acrylic foam tapes designed for use in structural glazing applications in lieu of structural silicone caulk to bond the IGU to the unitized frame and provide a primary seal, along with the structural bond.
These tapes have excellent elongation, high tensile and shear strength needed to support the high stresses resulting from supporting large insulated glass units (IGUs). This glazing tape enables clean, straight sightlines. It can be hand applied, or applied with the assistance of a tape applicator.
The dry adhesive system vs. a liquid silicone sealant enables these structural glazing tapes to be applied in a controlled, shop glazing environment with very short cure times (minutes vs. hours, or even days for some structural silicone sealants). This allows for the movement of the finished product immediately after glazing from horizontal to vertical, saving both fabrication time and valuable shop space, particularly beneficial when large orders are running through the shop and space is at a real premium.
SGB, SGG and SGW are available in 0.090” thickness. AFTC provides a very useful SG Glazing Tape Selector to specify the correct width (or bite) of tape, based on the wind load the tape will need to withstand.
Before applying these structural glazing tapes, the surfaces should be scuffed with a light abrasive pad and cleaned using an isopropanol/alcohol solution, always wiping in the same direction, to remove any possible debris or contaminants. MEK, Heptan or Acetone cleaners should be used on heavily contaminated substrates. Primers are available and should be used to assure ultimate bond strength.
Hand-held and automated devices are available to assist with application. These devices will assure proper, uniform pressure is applied when laying these tapes down and in final assembly of IGU to frame. Uniform, consistent pressure is critical to getting good wet out and even bonding. When applied using the proper techniques and primers, SGB, SGG and SGW structural glazing tapes provide good structural bond and seal, which can withstand the highest wind loads and will achieve the highest architectural ratings for any glazing system, AAMA AW 100 or higher.
Silicone Structural Glazing for Curtain Wall and Cladding
Silicone structural glazing requires applying a spacer tape to aluminum or steel mullions, setting the insulated glass over the spacer tape, then pumping structural silicone around the entire perimeter of the unitized panel in the gap created by the tape between IGU and the mullion. The structural silicone has to fully cure before the unitized frame can be sent out to the field for final installation.
The unitized panels, consisting of the horizontal and vertical aluminum mullions are assembled to the IGU, using a system similar to the one shown in Figure 3. The tape creates a uniform gap all the way around the frame, then structural silicone caulk is pumped into the gap between the aluminum and the glass.
In this design, the silicone becomes the primary structural element and the primary seal. The tape acts as a spacer and a secondary seal. Once the unitized frames have fully cured, they can be moved to the site, where they are installed one at a time in a linear fashion, using a backer rod and silicone caulk in between the panels.
Most silicone structural glazing is now done inside, in a temperature and humidity controlled environment, where the unitized panels are fabricated. This process is called shop glazing and is the way that almost all 4-sided glazing is done, which is the clean all glass look that can be seen on many high rise buildings.
A similar technique is used in most 2-sided glazing designs, but instead of the unitized panels being bonded on all four sides to give that all glass façade, the panels are aligned horizontally. This is commonly done in a track system. The only place where the panels would need to be joined is at the vertical seam, not the horizontal seam. Both 4-sided and 2-sided glazing require the use of a silicone structural glazing tape to create a uniform space between the aluminum frame and the IGU.
SGT T2040 Polyurethane Structural Glazing Tapes
SGT T2040 polyether polyurethane structural glazing tape has an excellent single or double sided acrylic adhesive system. The open cell, microcellular structure enables the foam to breathe, yet it is dense enough that it behaves in many ways like a closed cell foam, shedding water.
SGT T2040 single adhesive glazing tape is the most popular for shop glazing applications. The tape can be adhered to the unitized frame, with the uncoated foam exposed on top, most often in a horizontal orientation. The IGU can then be placed on top of the tape and repositioned easily to get the exact alignment to the frame. Silicone caulk must be carefully applied to assure a complete seal to the frame.
This glazing tape is an ideal spacer tape for silicone structural glazing, as it is very firm, and enables very uniform and rapid curing of the structural silicone. It is flexible, thermo-formable and dimensionally stable. SGT is available in black in 1/16”, 3/32”, 1/8”, 3/16”, 1/4", 5/16”, 3/8”, and 1/2" thick.
Double sided adhesive SGT T2040 tape may be specified in 2-sided or even 4-sided silicone structural glazing designs. The double adhesive system stabilizes the unitized frame, which enables the panels to be moved shortly after glazing, or in the event the IGU may shift after the glazing process is done. The double adhesive also provides a secondary seal to prevent moisture, construction debris or dust from getting into the glazing pocket, between the tape and the glass.
Which Glazing Tape is Right for You?
A glazing detail will point the buyer in the right direction as to which type of glazing tape to use. By knowing the type of glazing required, the user can quickly narrow down the field of possible glazing tapes to one or two that would be the optimum tape for a specific application.
In drop-in glazing details, either BGT, 15# or 25# PVC glazing tapes can be specified as a primary seal. In this type of glazing, either BGT or 15# PVC glazing tapes can be used in conjunction with a bead of silicone caulk as a heel, toe or cap bead to provide additional structural integrity and a secondary seal.
BGT is specified over PVC in drop-in glazing when an economical glazing tape is needed. White BGT is used over black PVC in windows and doors made from white extrusions.
15# PVC is chosen over BGT when a thicker tape is required. It can go up to 1/2” thickness, vs. 1/8” max thickness for BGT. The lower compression set characteristic also makes 15# PVC a more desirable tape to choose when expansion/contraction of the entire fenestration product is a concern. PVC provides better sound absorption qualities suited for high end commercial or residential windows and doors.
Structural glazing, using SGB, SGG or SGW glazing tapes can be used in lieu of silicone when clean sight lines are required. This type of structural tape glazing also enables the unitized frames to be moved quickly after glazing, saving time and valuable shop space. This type of glazing requires a bit more preparation and there are fabrication aids that can be used to assure uniform wet-out of the adhesive and consistent pressure to provide the optimum bond.
Silicone structural glazing, utilizing SGT T2040 glazing tape is most commonly used in large commercial fenestration projects, where unitized frames are fabricated using a spacer tape along with a structural silicone. The SGT T2040 glazing tape is available with adhesive on one side, to facilitate shop glazing when the IGU needs repositioning. SGT T2040 with adhesive on both sides is used when the unitized frame needs to be moved quickly after fabrication, a secondary seal is desired, or the additional structural integrity is required.