Facades: Beauty Starts Skin Deep

The first chance a building has to make a statement is with its exterior. What that statement is partially depends on the materials and systems used, and how they’re incorporated into the designer’s vision.
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Sponsored by CL-TALON®, Construction Specialties, Guardian Glass, and New Millennium Building Systems
By Peter J. Arsenault, FAIA, NCARB, LEED AP

Integrated Cladding Support Systems

Recognizing the issues and limitations of conventional support systems, new cladding support systems have emerged on the market that incorporate simplified, accurate installation guidance and thermal isolation within the system. These new systems have been designed to work with any type of cladding material for both interior and exterior applications. They can be installed both vertically as well as horizontally depending on the project requirements using specially designed attachment configurations that allow different fastening and connection techniques. Some even provide a coplanar, zero-sightline surface based on minimizing the depth of the members to match the thickness of continuous insulation.

During installation, these advanced systems provide a number of time-saving benefits to the contractor/installer. First, standard sizing of the components is available based on common 10-foot lengths spaced every 16 inches on center. Second, some include integrated measurement scales (in inches) to allow for quick, hassle-free placement and adjustment of other components and cladding. Similarly, leveling and plumbing of the system is accomplished with lightweight interlocking levels into the framing to ensure the system is plumb and true. In terms of sequencing, portions of the system can be staged and partially assembled prior to being installed on the wall or ceiling surface, saving time and ensuring proper placements of components. Finally, integrated attachment grooves allow for quick placement and adjustability of cladding attachment components. All of this creates a precise substructure on which the final facade cladding material can be attached faster, easier, and with potentially fewer errors compared with conventional systems.

High-Energy Performance

In order to assure the effectiveness of continuous insulation between the cladding and the exterior sheathing surface, the inner and outer members of the substructure are connected but kept separate using a clip system. In a high-energy performance system, these clips are available in adjustable depths, allowing the system to accommodate a wide range of exterior continuous insulation of various depths to meet project specifications. For best performance, these connection clips should be made from a material with a low thermal conductance such as polyamide, which is a common nylon composite material. Polyamide is routinely used in curtain walls and window industry products for its low thermal conductance, enhanced durability, and strength. It is also fire rated and will not crack, splinter, or warp. Engineering analysis, based on computer modeling, has been done on such high-performance systems in exterior wall assemblies with continuous insulation between the cladding and sheathing interrupted only by the polyamide clips. The conclusion of that analysis states, “The effectiveness of the overall assembly (thermal transmittance of assembly with thermal bridging vs. thermal transmittance of the assembly with no thermal bridging) ranges from 77–91 percent effective depending on insulation thickness and component spacing.”2 In terms of life-cycle energy impacts, most of the system components are responsibly sourced and 100 percent recyclable, allowing them to contribute toward various LEED credits or other green and sustainable building rating systems.

Photos courtesy of CL-TALON®

Polyamide clips with very low thermal conductance properties allow inner and outer aluminum members to be separated while controlling thermal bridging and allowing for variable depths of continuous insulation.

Testing and Code Compliance

High-performance cladding support systems often need to be tested in conjunction with the other materials in a facade assembly to demonstrate performance to meet or exceed minimum code requirements. These include NFPA 285 Standard Fire Testing, which must be done on the entire assembly, not just on individual products. Nonetheless, such high-performance systems have been shown to work exceptionally well with many common exterior wall assemblies when tested. Similarly, Air Pressure, Water Penetration, and Structural Performance testing, (ASTM E-283, ASTM E-330, ASTM E-331) has demonstrated performance beyond the levels required by building codes. This helps ensure that the cladding support system will function in normal as well as extreme weather conditions. Structural testing also indicates the ability of the cladding support system to safely transfer the imposed loads from both gravitational and wind forces affecting it to the structural members of the building.

Space Savings

One of the design and long-term financial benefits of high-performance cladding support systems is the ability to be compact and thus save space. This can come about in three ways. First, prior to installation, the compact nature of the system components require only a small space for staging and storage on site. Second, the design and strength of these systems remove the need for additional layers of cross bracing or cladding attachment rails to be installed. And third, due to the vertical and horizontal coplanar zero sightlines of the system face, the overall envelope footprint can be reduced, thus maximizing the usable/rentable square footage of a project. This thinner profile also helps to avoid encroaching upon the lot lines and air rights of any surrounding structures.

Overall, high-performance cladding support systems, are being recognized as the next generation of cladding support due to the multiple positive attributes discussed. Stewart Jeske, MS, PE, is a principal and senior glazing systems engineer at JEI Structural Engineering, says, “I’m impressed, and I think that this [type of] product will soon become the standard in the industry.” Facade contractors are weighing in too, including Erick J. Prifti of Albco, who says, “We installed a high-performance system in only three days, whereas with a traditional installation, it would have taken two weeks. We are very impressed with the speed and simplicity of the system.” All of this points to the need for architects to be aware of this technology and evaluate it for their particular projects.

Glass and Energy Performance

All occupied buildings require or desire natural daylight and views, hence the use of glass in building facades is ubiquitous. Indeed, some design approaches focus on “building with light” to create facades that capitalize on daylighting and views. The positive human effects of doing so have been documented in numerous studies that indicate the presence of glass in a building facade is essential for occupant health and well-being. There are also functional performance aspects of glass in a building facade related to occupant comfort and energy needs for artificial lighting, heating, and/or cooling in a building. Depending on the system installed, daylighting can lower energy use for lighting and related HVAC use up to 80 percent.3 In the process, the proper selection of glass can offer occupants comfortable, functional spaces that meet the program needs of the building and achieve the sought-after health and energy benefits.

Photos courtesy of Guardian Glass/© Luc Boegly; photo courtesy of 5+1AA Alfonso Femia Gianluca Peluffo architectures (left); photo courtesy of Eli and Edythe Broad Art Museum (right)

Selecting glass for a building facade requires consideration of a number of factors, including building shape, climate, energy codes, color, reflectivity, and panel size. Such was the case for the Broad Art Museum (right) designed by Zaha Hadid Architects.

The advancement of glass technology in the past few decades has addressed all of these building and facade aspects. That now means architects who are seeking to build with light needn’t sacrifice design intent and window-to-wall ratio in the name of energy performance. High-performance, low-e glass coatings can be used to help ensure buildings are able to manage HVAC loads while still offering the aesthetic needed with clear views for occupants. In order to fully achieve the intended results, facade design that incorporates glass must consider the following:

  • Building shape and orientation: Natural sunlight will hit building elevations in very different ways depending on the shape of the building and the compass orientation of each facade. Direct and indirect daylight will also enter the building differently at different times of day and during different seasons, all of which will impact energy use and occupant experience. The use of different glass coatings on different facades is one solution for managing solar heat gain, glare, and other factors in a consistent manner, regardless of these variables.
  • Climate-based energy codes: The International Energy Conservation Code (IECC) identifies eight different climate zones around the United States and prescribes performance criteria specific to each climate zone. Such criteria includes glass and glazing, thus requiring architects to identify the appropriate climate zone where the building is located and select glass according to the minimum criteria of that climate zone. Whether new construction or retrofit, the design team can select a high-performance, low-e coated glass product that will deliver the needed performance characteristics most appropriate to the climate needs.
  • Color and reflectivity appearance: Coated glass comes in many tints and offers different degrees of reflectivity, sometimes affected by the glass substrate used and sometimes by the coating. For new construction and retrofits, a range of clear, blue, green, and grey colors are available to suit different design schemes. For existing buildings, it is possible that the facade color and/or reflectivity of replacement glass, or new glass that is part of a new addition, needs to match or be consistent with existing glass. In those cases, large-size samples viewed at the building site will help the building team identify the best coated glass product.
  • Glass panel size: While it is possible to manufacture glass in a variety of sizes and thicknesses, the equipment to add coatings has had historical size limits. That has changed with the availability of new coated glass in jumbo sizes on lites up to 217 square feet. Standard jumbo coated glass products can now be specified up to 130-by-204-inch sizes, with special orders available at 130 by 240 inches. The lites are available in 6-, 8-, or 10-millimeter thicknesses and on jumbo float glass that is clear, tinted, or low-iron.

The larger-size jumbo glass in particular has become appealing for many commercial buildings because it opens up possibilities to architects by delivering expansive views while maintaining high performance. It amplifies all of the benefits and the impact of glass facades by making indoor spaces feel more expansive and giving people inside the buildings access to extraordinary, uninterrupted views of the outside scene. With large-scale jumbo glass, the boundaries between indoors and outdoors recede, and the illusion—the connection—is complete. Further, by using clear, low-iron glass as the substrate for jumbo lites, those expansive views are free of the green tint that exists in standard glass. It also delivers clean lines, true colors, and clear views with no distractions, maximizing light transmission to bring natural light deep into interiors. Darijo Babic, director of architectural sales, North America for Guardian Glass, observes, “While the trend of architects designing projects with larger glass sizes continues to grow, we also see architects designing large projects with very high volumes of coated glass. Architects can now capitalize on 20 years of jumbo coated glass experience combined with our high-performance low-e coated glass.”

Glass product lines for commercial applications give architects a range of excellent solar control capabilities and a wide variety of colors and performance levels. Those glass products offer innovative, leading solutions for appearance and energy efficiency in facades and are commonly available through local fabricators.

 

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Originally published in Architectural Record

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Academies
Facades: Beauty Starts Skin Deep
Buyer's Guide
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Where other attachment systems rely on rails to be anchored through the substructure and insulation into the building frame, thus creating thermal bridges, CL-Talon minimizes thermal bridging. This provides optimal thermal performance through a combination of exterior insulation and thermal clips, which reduces thermal bridging and therefore additional thermal breaks.
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