Outside the box: plastics can help green up the exterior.
In many cases, the insulating properties, durability, and aesthetics of plastic make these products a commonsense choice for commercial building exteriors. They can help reduce building energy consumption, reduce or eliminate the need for harsh cleaning compounds and paints, and provide unique aesthetic appeal over the life of the building.
Both spray polyurethane foams (SPFs) and exterior insulation and finish systems (EIFS) can help contribute to superior energy efficiency while creating facades with character and beauty. SPFs can be applied-usually as one-step, two-component, sprayed-in-place rigid foam-over structural supports of virtually any size and geometry.
These products can give a building owner nearly unparalled creative freedom. They can also help keep construction methods straightforward, even as they help to produce a facade that is lightweight and easy to finish with a durable cladding. EIFS, whether applied over a complicated 3-D shape created with SPF or over a more traditional rectangular flat structure, typically consist of the following components:
* Insulation board, made of polystyrene of polyisocyanurate foam, secured to the exterior wall surface with a specially formulated adhesive and/or mechanical attachment.
* A water-resistant base coat applied on top of the insulation and reinforced with fiberglass mesh for added strength.
* A durable finish coat--typically using acrylic copolymer technology--which is both colorfast and crack resistant. SPFs and EIFS, applied properly to the exterior of the structure, can act as an effective air barrier, reducing air infiltration substantially. They can also increase total R-value across the walls, improving occupant comfort and reducing building energy consumption, which may, in some cases, allow the specification of smaller-capacity HVAC systems. Lower energy consumption can provide environmental benefits over the life of the building.
EIFS exteriors can resemble stucco of stone, and provide a wide latitude of finishing options. They can be specified in virtually limitless colors and a wide variety of textures, and can be fashioned into nearly any shape or design-most of which is computer-generated-for detailing.
Moreover, EIFS rarely need painting. Most EIFS exteriors are specially formulated with a 100-percent acrylic binder, which provides superior resistance to fading, chalking, and yellowing, so the systems tend to maintain their original appearance over time. Since the color is integral to the finish coat, the same color appears beneath an abrasion. The finish coat also exhibits excellent resistance to dirt, mildew, and mold.
Plastics-based facades are also dimensionally flexible, which contributes to their longevity. When walls expand or contract with changing temperatures, plastics-based exteriors can be resilient enough to "absorb" building movement and avoid the unsightly cracking problems that can be common with less flexible exteriors.
Overall, plastics may represent one of the best combinations of environmental footprint, aesthetics, longevity, and ease of construction for commercial building exteriors.
Plastic Composites and the Environment
Composite materials, which typically combine plastics with a variety of natural materials, plus post-industrial and post-consumer waste (both natural and synthetic), are increasingly helping to lower the environmental impact of commercial buildings.
Objective life-cycle studies show that composites can provide better performance, life, durability, and economics, with lower consumption of natural resources, than many of their all-natural counterparts-in both new construction and renovation.
For example, vinyl has been combined with sawdust to form exterior trim that resists rot, mildew, and weathering. It can be molded into a wide range of designs, geometrics, and colors, and doesn't require painting or the use of harsh cleansers to clean or restore it. Composites, while exploiting the look and feel of traditional materials, almost always depend on the performance characteristics, durability, economics, and longevity of plastic binders.
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Want more information on a variety of exterior and structural products? Circle Inquiry No. 714 on the Free Product Information Card, page 65.
Mike Levy is executive director of the polystyrene packaging council and expandable polystyrene supplier council at the American Plastic Council Inc. (www.americanplasticscouncil.org), headquartered in Arlington, VA.
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|Title Annotation:||The Building Envelope|
|Date:||Nov 1, 2003|
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