Today's Multiwall PC Technology Integrates Aesthetics, Sustainability and Economy

Today’s multiwall offerings include sophisticated finishes, a wide array of colors and superior structural capacities.

The industry saw a 5% increase in 2009, in the middle of a major recession. The multiwall market estimates an 8% increase in 2010. There are sound reasons for this:

Green building is now the norm; daylighting is an increasingly important component, and many applications don’t require a view.

Traditional direct daylighting with glass can create glare, hot spots and solar gain, which in turn create uncomfortable, unproductive environments and high operating costs.

Diffuse daylighting provides the benefits of natural lighting – and projects it 33% deeper into a space – as it eliminates these disadvantages.

Structural capacities allow for engineering systems that can withstand the impact of hurricane-velocity winds and will pass large-missile impact tests.

Multi-wall sheet products can integrate with other new technologies that enhance performance, especially energy efficiency.

Improvements in weatherization and fire safety have made multiwalls a more attractive alternative in commercial, industrial, educational and government facilities. Many carry a CC1 – Class A fire rating. Most have UV protection co-extruded into the sheet, preventing discoloration and light loss.

Architects and designers are now appraising this previously overlooked material and appreciating what they see in aesthetics, energy efficiency and economy – often with initial costs one-third to one-half less than traditional alternatives.

While three primary suppliers provide the resin worldwide for multiwall sheet extrusion, each extruder enhances the product with its own, often exclusive, features. Finishes vary widely. The slick, high gloss of previous multiwalls has been replaced with textured finishes in hammered crystal and satin mattes. Colors range from standard blue, green, bronze, opal and clear to lavender, red, yellow, gray and more. Specialties include sheets with a structural “rippling wave” effect. Thicknesses in 6mm to 40mm+ provide Uvalues down to 0.19 with Rvalues up to 5.26. Light transmission can reach 92%. And the material is 100% recyclable.

Exceptional energy efficiency can be achieved by filling the sheet’s cells with a new translucent aerogel that doubles the thermal value, while maintaining high light transmission. Another new technology in spectrally selective coatings places a transparent film in the cells’ interior, blocking up to 95% of infrared rays, 99% of UV rays and up to 85% of solar energy, while maintaining light transmission to 65%.

Design versatility is major factor in multiwall’s growing popularity. The sheets, which can be ordered up to 39’ in length, cold-form easily in dramatic curves. The translucency enables a designer to use backlighting, including low-voltage LED arrays, to create environments that soothe, excite and inspire occupants. And the lighter weight in this shatterproof material allows for larger spans with less support required.

Today’s translucent multiwall technology lends itself to a wide range of applications from skylights to vertical glazing of all types to canopies to interior walls.

Industrial applications are just one prime example. When Duo-Gard Industries Inc, located in Canton Michigan, updated its headquarters in late 2009, it replaced 13-year-old multiwall clerestories with today’s advanced technology. The company is a leading innovator in developing high-performance translucent daylighting systems for the architectural market.

“We practice what we preach,” said David Miller, Duo-Gard’s President. “Today’s multiwall performance and aesthetics far outpace yesterdays. Our previous system required a layer of translucent thermal foam to achieve the desired insulation along with light transmission. This created some problems that we wanted to eliminate.”

Duo-Gard selected a 20mm tongue-and-groove multiwall glazing from Co-Ex Corporation for the replacement. Now the 20,000 square foot facility sports a clerestory 12’ high by 275’ long on its south and west elevations. The west wall includes a 20-foot-wide section of operable panels for ventilation.

Miller said the mullionless tongueand- groove system in the opal tint chosen enhances the facility’s facade as it allows 47% visible light transmission, and the 20mm thickness carries a 0.35 U-value, R-4 thermal rating. “This gives us more light – usable, diffused daylight - with the same thermal value as before,” he said, adding that the plant’s long banks of metal halide lights are never on during days with adequate sunlight, resulting in a 33% - 50% savings in electricity. Installation of the tongue-and-groove system took only 7 days instead of an estimated 11.

Along with the advantages of today’s multiwall polycarbonates come some cautions. The material’s UV-protected surface must face out. A multiwall system must be dryglazed. Because it has a higher coefficient of expansion than glass, it requires special framing systems engineered to accommodate this factor. Multiwalls must “float” in the frame: standard framings for glass grip too tightly to allow this. Although it’s virtually shatterproof, the material can be scratched, so specifiers need to choose applications carefully and select an appropriate surface texture. Because of the material’s diversity in performance and aesthetics, it’s important to be sure the choice of material effectively suits the proposed application.

Properly evaluated and applied, today’s multiwall polycarbonate technology gives those involved with the green building movement an opportunity to combine exceptional aesthetics, energy efficiency and economy in daylighting.

For more information, contact Kurt Glazer, CO-EX Corporation, 5 Alexander Drive, Wallingford, CT 06492, 800-888-5364, Fax: 203-679-0600, E-mail: info@co-excorp.com. Web: www.co-excorp.com.