Cool and green
July 5, 2007
Like most successful contractors, you’re probably looking for new markets and ways to expand your business.
One of the new areas of potential is the growing “sustainability” movement, defined as development that balances the fulfillment of human needs with the protection of the natural environment.
Architects and general contractors nationwide are embracing sustainable design and the U.S. Green Building Council’s Leadership in Energy and Environmental Design standards program to select environmentally sound building products for their projects.
Metal-roofing products contribute importantly to the sustainable building movement. The metal, as well as the “cool” coatings - so named for their ability to reflect the sun’s heat - in such roofing systems can provide the energy efficiency, and recycled content necessary to qualify for points in the LEED program.
For those interested in building environmentally sound structures, LEED provides economic and social incentives. And a LEED-compliant metal roof can be a major part of so-called green buildings.
Heat ‘islands'The most widely known credit for roofing under LEED is No. 7.2, for roofs reducing the “heat island” effect, worth one point in the LEED code. Urban areas produce this occurrence, with dark, heat-absorbing roofs being among the chief culprits. The temperatures in the air above these locations with their hot, black roofs can be as much as 12°F hotter than the surrounding suburbs. This can lead to higher air-conditioning costs, greater use of electricity and unhealthy levels of smog and ozone.
Cool metal roofs can reflect heat well across the entire solar spectrum, especially in the infrared and visible wavelengths. The less solar radiation materials absorb, the cooler they are. In addition to absorbing less heat, some cool-roofing materials radiate away any absorbed heat. New infrared-reflective pigments incorporated into paints used on cool metal roofs allow them to achieve higher reflectivity values, even in darker colors such as black and brown. This improved reflectivity can mean a much cooler surface temperature and greater energy savings for the building below.
The content of steel and aluminum used in metal- roofing material is comprised of substantial amounts of recycled materials, making them an excellent candidate for LEED credits focused on recycled materials.
Recycled contentMetal is the world’s most recycled material. The North American steel industry’s overall recycling rate is 71 percent, according to the Steel Recycling Institute. An Aluminum Association survey in late 2003 indicated that the recycled content of domestically produced, flat-rolled aluminum for the building and construction market was approximately 80 percent to 85 percent. Aluminum alloy Type 3105, the aluminum product used in most standing- seam metal roofs, is produced from 99 percent scrap, 80 percent of which is from post-consumer sources.
LEED credit 4.1 is designed to increase demand for building products that incorporate recycled materials. Building projects with a metal roof can earn one LEED credit for meeting the qualifications and can pick up an additional credit if the sum of the roof’s post-consumer recycled content plus one-half the pre-consumer content constitutes an additional 10 percent or a total of 20 percent of the roofing material based on its cost.
Metal roofs can also qualify for regional materials credits if 10 percent of the materials are extracted, processed and manufactured nearby. A project can earn a credit for 10 percent of the material and an additional credit for 20 percent as along as the material is “extracted, harvested or recovered as well as manufactured within 500 miles of the project site.”
If you and your architect are seeking such credits, ask your metal-roofing supplier to provide proof of where the metal substrate was manufactured and if it was within 500 miles of the project location. This permits architects and developers submitting LEED projects to include in their spec-and-bid packages a clear picture of the material’s origin.
These credits represent a direct way for metal roofing to earn LEED credits. However, there are other LEED credits where metal roofing products may play an indirect role in qualifying as well.
Less wasteMaterial-recycling credits Nos. 1.1 and 1.2 for building reuse are intended to extend the life of existing building stocks, and reduce waste and the environmental impact of materials manufacturing and transport. The two credits require that the owner or developer maintain at least 75 percent and 95 percent, respectively, of the surface area of an existing building’s structure, including structural floor and roof decking and the building “envelope,” including structural roofing material.
Nonstructural roofing material is excluded. The intent is to reuse an existing, previously occupied building. Peak roof structures built with metal standing-seam materials clearly have a much stronger opportunity for reuse than flat roof structures and asphalt.
The use of metal-roofing products also play an integral role in three other credit classifications, each involving the conservation of water resources.
Designed to reduce or eliminate water usage, LEED’s water efficiency credit Nos. 1.1 and 1.2 encourage efficient landscaping and call for the reduction of potable water by 50 percent or 100 percent, respectively, for project landscape irrigation. Each credit suggests the use of captured rainwater. Other credits call for maximizing water efficiency in sinks, toilets, showers and lavatory faucets. The credits suggest the reuse of storm water for non-potable applications such as toilet and urinal flushing and custodial operations.
In the case of these credits, one of the superior ways of reclaiming and reusing non-potable water is through use of Kynar-coated standing-seam metal roofing.
Saving waterWater collection of non-potable water depends on such factors as roof material, diversion amount and design retention. The smoother, cleaner and more impervious the roof surface, the higher the water quality and the greater the amounts of water that can be collected. Coated metal and aluminum roofs have a collection efficiency of more than 95 percent. Shingle roofs with their porous or rough roof surfaces hold back some of the water that would otherwise make it into a recovery system. Concrete roofs lose an average of about 10 percent and built-up tar-and-gravel roofs lose as much as 15 percent. Flat roofs can retain as much as half an inch of rainwater.
Wood shakes, concrete or clay tiles, and asphalt shingles are more likely than other materials to support the growth of mold, algae, bacteria and moss, which can potentially contaminate water supplies. Treated wood shingles may leach toxic preservatives, and asphalt shingles may leach small amounts of petroleum compounds.
Many government agencies suggest metal roofs as the preferred material for potable water use, provided they do not contain lead, zinc coatings or copper. And they identify specific metal roof materials as a solution for collecting potable water, including stainless and galvanized steel.
Solar powerMany architects now recognize the value of solar power and LEED offers several credits for solar projects that save energy. Architects leery of solar systems because of their unattractive design should realize that picture is changing. New photovoltaic and solar thermal technologies are emerging that are much simpler to install and have been designed to work specifically with standing-seam metal roofing.
The use of photovoltaic material meets the requirements of LEED’s energy-and-atmosphere renewable energy credit, which incrementally awards up to three points for generating 5 percent, 10 percent or 20 percent of the building’s energy use with renewable power.
Another credit awards up to 10 points based on percentages of energy-cost reductions. For example, a 60 percent reduction will earn the maximum 10 points and is likely attainable with use of a metal-roofing system with an integrated photovoltaic system. The project team gains a credit for successfully demonstrating energy-cost savings of 10.5 percent and one point for each additional 3.5 percent saved. The energy-efficiency gains created by the solar thermal technology are also available for LEED credits.
Breakthroughs in photovoltaic design and thermal technology and the ability to coat metal-roofing materials in custom colors have produced roofs that are attractive, virtually invisible to the naked eye and work very effectively together.
PhotovoltaicsOne example is the newest photovoltaic material, an extremely lightweight and unbreakable self-adhesive laminate substance less than a quarter-inch thick that is attached to the standing-seam panels with a hand roller. They are made exceptionally durable by encapsulation in ultraviolet-stabilized polymers. The material is bonded to standing-seam roofing panels, which can be coated in the same color as the laminates. They are then installed on any south-facing roof with good solar access. The laminates can be attached before or after the standing-seam material has been installed and in many cases, provides all the electricity a building needs.
The newest solar thermal collection system is comprised of a 1-inch-thick conductor that employs glycol-protected fluids to collect and transfer solar energy to building systems using closed-loop heat-exchange technology. The system is concealed under the standing-seam metal roof laminated with the amorphous silicon photovoltaic system. Upon completion, the system becomes an integral part of a hardened building envelope that provides storm resistance, energy security and lower operating costs by replacing fossil fuels and electricity with solar energy.
Because they are fully integrated, they reduce cooling loads on buildings and can directly contribute to process and space cooling by dissipating excess heat through radiational cooling.
Building owners can realize immediate benefits from the reliability and operational simplicity of these modern, integrated mechanical systems.
Ultimately, a standing-seam metal roof presents architects and builders with a sure way to collect several credits in designing a LEED-accredited project. When amassed with other rating points for various sustainable features, a standing-seam metal roof is a cost-effective way to meet requirements. The simple act of specifying a metal roof can accumulate five LEED credits for reducing the heat-island effect and for recycling and regional material usage. Add to that the ways in which metal roofing can help achieve additional credits for water reuse and renewable energy, and you have a solid base to easily gain LEED points that can earn federal, state and local incentives.
The opportunity for contractors to expand their business is there. And while sustainable projects may not represent the base of any contractors’ businesses, they are an area of growth they should be investigating.
This article and its images were supplied by Englert Inc., a Perth Amboy, N.J.-based manufacturer of metal roofing materials.