Shared Learnings: Controlling Storefront and Curtainwall Water Infiltration

by Tom Minnon, LEED® AP, CDT, Eastern Region Sales Manager for Tubelite Inc.

Most architectural aluminum glazing systems are not designed to be totally waterproof. Rather, most systems are designed to control water infiltration under extreme conditions and weep that water back to the exterior. Storefront and curtainwall systems differ in many ways: appearance, profiles, wind load resistance, glazing, thermal performance and how they weep water. This discussion focuses on how storefront and curtainwall handle water disbursement differently.


Storefront systems control water infiltration by directing all moisture to the sill flashing (1). It is imperative that the sill flashing be installed correctly. Most aluminum manufacturers have introduced high-performance sill flashing designs that allow the installer to fasten the flashing to the bottom of the opening prior to installing the storefront framing. A watertight seal can then be applied over the fastener head (2). The sill then sets on top of the flashing with no need for fasteners penetrating the sill flashing. Unlike the old sill flashing designs, these high-performance sill flashings utilize two weep holes in the sill flashing at each lite of glass (3). These extrusions also have a much higher back leg for better water performance, and it is important to make sure that sealant is applied to the top of the back leg prior to installing the sill (4).

Improper sill flashing

Assuming that the sill flashing is installed correctly, the most important element in controlling water penetration with storefront is the proper fastening and sealing of end dams (5). Without end dams, water will intrude into the jamb locations of the building. In the photo below you can see where improperly (or missing) end dams have caused significant water damage to the interior drywall, even though sill flashing was present.

Storefront water deflector

Water deflectors must be installed wherever a horizontal mullion occurs in storefront. These direct any water that reaches the horizontal over to the vertical mullion where it weeps out at the sill flashing. Deflectors are necessary to ensure that the water bypasses the lite of glass below the horizontal. Without water deflectors, moisture likely will settle on the top of the glass, allowing water to enter the interior and causing possible failure of the insulating glass unit.



With curtainwall, we want to prevent any water from reaching the vertical mullion. Each horizontal mullion must have zone dams (sometimes called “joint plugs”) properly installed and sealed at the vertical. Any water that makes its way to the vertical mullion ultimately will end up on the interior of the building.

Unlike storefront, which directs all water to the sill, curtainwall weeps water at each individual lite of glass through holes in the pressure plate. Because most curtainwall systems are used on taller elevations with higher wind loads, the amount of water entering the system is typically greater than the capacity of strorefront mullions and sill flashing. This is why each lite of glass is individually weeped. There are critical steps that must be taken to ensure that no water penetrates a curtainwall system.

Each pressure plate must have two weep holes ABOVE the horizontal tongue (1). Similarly, each face cover requires two weep holes (2). All too often, field failures of curtainwall are directly due to improperly installed zone dams or incorrect placement or missing weep holes.

Since water is not directed down the vertical mullions to the sill, curtainwall does not require sill flashing. However, care must be taken in handling the caulk joints at the sill. The exterior caulk joint must be behind the face cover since water is weeping out of the bottom (3). A common installation error is mistakenly applying caulking to the exterior sill and blocking the weep holes.


So, how can you ensure that a storefront and/or curtainwall system is being installed correctly?

  • Have the manufacturer’s installation instructions be included with the glazing subcontractor submittals. This will provide the architect, engineer and or general contractor a resource for field checking the installation, and they become part of the Construction Documents.
  • Carefully review submitted shop drawings. Ensure that the details correspond with the manufacturer’s recommended installation instructions.


Glass Association of North America
National Glass Association
Whole Building Design Guide, Building Envelope Design Guide


Tom Minnon, LEED® AP, CDT, is the eastern region sales manager for Tubelite Inc., serving clients from Maine to Georgia. With nearly four decades of industry experience and many professional accreditations, he regularly provides educational and consultative support to architects, buildings owners and glazing contractors regarding storefront, curtainwall, entrances and daylight control systems.


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Tubelite in two places at once: CSI CONSTRUCT, GlassBuild America

September 12-14, 2012,
Tubelite Inc. will be exhibiting at two industry events:
Construction Specifications Institute’s (CSI’s) CONSTRUCT show in booth #628 at Arizona’s Phoenix Convention Center,
GlassBuild America: The Glass, Window & Door Expo in booth #912 at the Las Vegas Convention Center.

Please visit us and learn about Tubelite’s newest products.

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Shared Learnings: AIA 2012 Preview

by Tom Minnon, LEED® AP, CDT, Eastern Region Sales Manager for Tubelite Inc. As the

American Institute of Architects (AIA) 2012 National Convention and Design Exposition opens in Washington, D.C., exhibitors will be showcasing new technology and products for use in the glass and glazing industry. One focal point will be increasing the thermal performance of commercial glazing systems. This has become paramount as new energy codes continue to be adopted and enforced. Here are some highlights from the exhibit floor.

Viracon’s VE 1-2M has these characteristics: 63% Visible Light Transmission 0.21 U-Value, 0.34 Solar Heat Gain Coefficient


Triple Glazing

Viracon, and other glass fabricators, offer triple-glazed units that minimize heat transfer improving overall thermal performance. However, while a third pane of glass adds to the insulating value of the assembly, it also reduces the visible light transmission (VT) and the solar heat gain coefficient (SHGC). Adding a low-E coating to a surface, or multiple surfaces, of the triple-pane unit will also increase the energy performance, but it may (depending on the type of low-E coating) affect the SHGC and VT. Filling the space between the panes of glass with argon and/or krypton gas will also improve energy performance.

A third pane of glass increases the weight and thickness of the unit, which can make mounting and handling more difficult and transportation more expensive. There are physical and economic limits to the number of glass panes that can be added to a window assembly and the thermal performance benefits diminish as well. Care should be taken to ensure that the architectural aluminum framing system can support the additional weight of triple-glazed units, which average about 10 pounds per square foot.
Booth 3825


Suspended Films

A suspended plastic film can be substituted for the middle layer of glass in a triple-glazed unit. The light weight of the plastic film is advantageous. Because it is very thin, it does not increase the unit thickness substantially.

Southwall Technologies’ Heat Mirror® technology is based upon a very thin coated film, which reflects heat back to its source. They offer 12 different films, which provide varying levels of VT and SHGC to meet the diverse requirements of the commercial market place.

Heat Mirror units can be produced with a wide range of glass substrates including clear glass, tinted glass and low-E glass. By taking advantage of the benefits of film-based coatings and glass-based technologies, they can create superior insulating performance and outstanding solar control, while blocking UV radiation, and reducing outside noise more effectively than double-pane glass.


Electronically tintable glass

Electronically tintable glass can be specified for windows, skylights and curtainwalls. It is an effective way to control sunlight without shades or blinds, so you can manage glare and heat, while maintaining a connection to the outdoors. SageGlass® offers a solution (electrochromic) that can be adjusted based on the end-users’ preferences. Pleotint, on the other hand, offers a solution (thermochromic) that automatically adjusts based on the sun’s heat.

Electronically tintable glass increases design freedom by removing sun control from the equation. Buildings can be infused with daylight without shades, blinds or louvers.
Booth 2003 and Booth 2318


Advanced Aluminum Glazing Systems

Manufacturers of aluminum storefront, curtainwall and windows have responded to the need for increased thermal performance by designing systems that will accommodate glass in thicknesses greater than the typical 1-inch units. Triple glazing is usually 1.75-inch thick (three each 0.25-inch panes of glass and two each 0.5-inch air spaces).

Wausau Window and Wall Systems, and others, can provide curtainwall and windows that will accept this glazing.
Booth 313


Lumira Aerogel

Cabot Corporation’s translucent Lumira™ aerogel maintains and enhances energy efficiency, while enabling a wide range of commercial and residential building design choices.

Aerogels are the lightest and best insulating solids in the world. Cabot’s Lumira aerogel is a hydrophobic aerogel produced as particles. Each particle consists largely of air (more than 90 percent) and is contained in a structure with pore sizes less than the mean free path of air molecules, which severely inhibits heat transfer through the material.

The inclusion of Lumira in daylighting systems virtually eliminates the historical trade-off of insulation vs. natural light by providing three to six times the thermal performance of traditional insulated fenestration products, while maintaining optimal light transmission. As a result, even large daylight surface areas can maintain high energy-efficiency by reducing thermal loads.
Several companies that offer Lumira will be exhibiting at the AIA Design Exposition.





Tom Minnon, LEED® AP, CDT, is the eastern region sales manager for Tubelite Inc., serving clients from Maine to Georgia. With nearly four decades of industry experience and many professional accreditations, he regularly provides educational and consultative support to architects, buildings owners and glazing contractors regarding storefront, curtainwall, entrances and daylight control systems.


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Connecting Architects to Online Specifications’ Tools

Assisting architects with specification writing and 3-D design, Tubelite Inc. participates in several online and automated tools. The company’s website connects visitors to product details, technical data and other information on its storefront, curtainwall, entrance and daylight control systems.

From, visitors with subscriptions to BSD SpecLink®-E‘s can link to automated specification writing assistance. Also within one click of Tubelite’s homepage, users can access Autodesk® Seek and CADdetails for Building Information Modeling (BIM) libraries.


Media contact: Heather West,

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Tubelite AIA/CES course menu

Addressing the architectural community’s professional development needs, Tubelite Inc. offers educational presentations available through the American Institute of Architects’ Continuing Education System (AIA/CES). As a leading manufacturer of storefront, curtainwall, entrance and daylight control systems, the company’s website invites architects and designers to explore its online resources at, and to connect with representatives in their area for in-person presentations.

Tubelite’s four, current AIA/CES presentations include:
* Product Selection Guide
* The In’s and Out’s of Architectural Aluminum Doors and Frames
* Green: Architectural Aluminum Products for Commercial Construction
* Modified and Custom Doors

Tubelite also provides the following Health/Safety/Welfare and Sustainable Design (HSW/SD) programs:
* Daylighting and Integrated Façade Design

* Understanding U-Factors

Each of these courses is available as one-hour, in-person presentations. Participants can receive 1.0 Learning Unit (LU) for each program.

To learn more about Tubelite’s architectural resources and educational tools, please visit


Media contact: Heather West,

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