The desire by clients and therefore

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1 ASCENT CASE STUDY 18 Precast Helps Projects Attain LEED Certification Precast s proximity, energy efficiency, recyclability and minimal waste are keys to meeting environmental standards that are gaining client interest The desire by clients and therefore designers to provide higher levels of environmental friendliness in their buildings is gaining popularity. Much of the attention is spurred by the Leadership in Energy & Environmental Design (LEED) standards created by the U.S. Green Building Council (USGBC), as well as by the growing attention to climate change and the consumption of energy and materials in the United States compared to other countries. To reach these goals, designers are turning more often to precast concrete components, which provide a number of green advantages. Park Service Uses Precast An example can be seen at the National Park Service s new 68,500- square-foot, three-story regional headquarters in Omaha, Neb. The federal department has a big stake in stressing the need to be environmentally aware, and the General Services Administration s request for proposal stressed this need. It emphasizes using environmentally friendly design in every possible aspect and requested a design that could achieve Silver (third-highest) LEED certification. Designers at Leo A. Daly Inc. in Omaha are striving to exceed that goal by achieving Gold (second-highest) certification, using a variety of techniques that included the use of precast concrete architectural panels. The key considerations come in such things as the positioning of the building and recycling activities done within the building, explains Patrick Pharmacia s Building Q in Skokie, Ill., designed by Flad & Associates, serves as the cornerstone building in the company s large-scale research campus. The building, which achieved a Gold LEED certification, features precast concrete architectural panels on its wedge-shaped façade. The facility was the first R&D lab in the country to achieve a Gold rating. Precast concrete components were provided by Nucon Schokbeton/Stress-Con Industries Inc. in Kalamazoo, Mich. Photography: Steve Hall - Hedrich Blessing /Flad & Associates 2004 Morgan, project manager. But we always intended to use precast concrete panels, due to the aesthetics they provide and the sustainability factors. The building features precast concrete insulated architectural panels attached to a cast-in-place concrete frame and a pci.org Click for more post-tensioned slab. The panels, supplied by Enterprise Precast Concrete, Inc. in Omaha, Neb., are finished on both sides, allowing the interior face to serve as the interior wall without additional finish or furring out. Some of the panels are radiused and create a frame that

2 surrounds the glass curtain wall on the two upper stories. The panels feature a buff color with a combination of light sandblasting and acid-etching. The panels helped achieve the LEED certification in a variety of ways, Morgan says. These included their ability to be recycled, local manufacturing capability and thermal mass and insulated cores. All of these attributes help reduce the expended energy needed to manufacture, transport and erect materials, which are key LEED requirements. In fact, precast concrete components can help reach as many as 23 of the 26 points needed to achieve LEED certification, according to Garrick Maine, project architect with Flad & Associates in Madison, Wis., and an accredited LEED professional. Key areas where precast concrete aids these qualifications come in these categories: Minimum Energy Performance (Energy & Atmosphere prerequisite #2). The building must meet ASHRAE energy-efficiency and performance requirements or the standards of a more restrictive local code, if it exists. The requirements for the ASHRAE standard are cost-effective and not particularly stringent for concrete, says David Shepherd of the Portland Cement Association. Requirements can be calculated from tables in Appendix B of the ASHRAE standard. Precast concrete s key benefit comes from its thermal mass, which helps the material store heat and moderate daily temperature swings. When that advantage is used in insulated sandwich wall panels, in which a layer of insulation is sandwiched between two wythes of a concrete panel, the material can produce high R factors and lower HVAC needs. In addition, large precast concrete panels have minimal joints, reducing uncontrolled air infiltration. These attributes can help a project earn as many as the maximum 10 LEED credits in the Optimize Energy Performance category of the standards. Thermal Mass Not Appreciated Despite vast empirical evidence, modern understanding about thermal mass has taken some time to evolve, says a report from the Environmental Council of Concrete Organizations (ECCO), of which PCI is a member. Few studies focused on the benefits provided by thermal mass prior to the oil crisis in the early 1970s, it explains, and The Midwest Regional Office of the National Park Service in Omaha, Neb. was designed to relate to the history of the nearby Missouri River, provide resources to support 13 surrounding states, complement the riverfront while achieving its own identity and act as a teaching tool for sustainable design. Designers at Leo A. Daly used precast concrete architectural panels for the façade, which were supplied by Enterprise Precast Concrete Inc. in Omaha, Neb. then prescriptive relief was addressed with readily available corrective measures, focusing on insulation with minimum R values. But R values neglect thermalmass characteristics, leading them to be underestimated, the report says. Recent studies, including one by the U.S. Department of Energy (DOE), has demonstrated the true benefit of thermal mass, ECCO says. The DOE report indicated that mass in exterior The combination of insulation with thermal mass forms a superior wall system. walls reduces annual energy costs in the building. The U.S. Department of Housing & Urban Development (HUD) and the National Institute of Standards & Technology (NIST) also have done studies, ECCO reports. Thermal mass also helps shift peak loads from midafternoon in the summer to after 5 p.m., when loads are reduced. Modeling and testing have proven that the combination of insulation with thermal mass forms a superior wall system exhibiting the benefits of both, ECCO says. The most benefit comes from placing the insulation inside the thermal mass, as in insulated sandwich wall panels. Adding insulation to the interior wall, the other commonly used approach, isolates the wall from direct contact with the interior, reducing the benefits of the wall s thermal mass. Regardless of placement in the wall, thermal mass reduces loads and shift peak loads in most climates, says Martha G. VanGeem, principal engineer and group manager for the Building Science & Sustainability Group at Construction Technology Laboratories Inc. in Skokie, Ill. The guiding principle for all thermalmass standards has been performance, whether of the individual components or the overall building envelope, says the ECCO report. These standards have successfully translated the behavior of thermal mass into understandable and easy-to-use terms. The result is that thermal mass has become a feasible element of building design. With precast s ability to aid in meeting LEED standards, the benefits of thermal mass will become more apparent to designers in the future. Building Reuse (Materials Credit #1). A one-point credit is available for maintaining 75 percent of the existing shell of a building, and an additional point is offered for maintaining

3 percent of the shell, consisting of the skin and frame but not the windows, interior walls and other components. Concrete s durability gives it a strong advantage in this category, as both a total-precast concrete structural system and structural or architectural panels can provide long life. ENVIRONMENTAL IMPACT Material Process Impact Concrete Aggregate Extraction 1.00 Limestone Quarrying 1.50 Steel Iron-Ore Mining We always intended to use precast concrete panels, due to the aesthetics they provide and the sustainability factors. Specific durability can be hard to quantify, because it depends on so many variables, says PCA s Shepherd. Those factors can include weather, maintenance and finishes. Compared to concrete, many other building materials simply don t last as long without significantly more maintenance. High-performance concrete is really the way to go if you want to achieve durability. Precast concrete s durability also can eliminate the need for interior partitions and exterior cladding, and the panels need to be recaulked only every 20 years or so. This reduction in the use of chemicalbased materials increases the building s environmental friendliness. In addition, because total-precast concrete systems offer long interior spans via double tees and hollowcore flooring, buildings are easier to remodel or reconfigure as tenant needs change. This ensures the structure can remain in place longer with only minor adjustments needed, which do not impact the LEED rating. Construction Waste Management (Materials Credit #2). This twopoint credit is available for reducing construction, demolition and landclearing waste that ends up in landfills. At least 50 percent of these materials must be kept out of landfills, and the second credit is offered if 75 percent Wood Boreal Timber Harvesting 2.50 is diverted. This credit can be used in conjunction with the Building Reuse credit to achieve as many as four points if existing materials on-site, such as precast concrete wall panels, are reused in the project. In that case, the materials preserved can be applied to this credit as well as to Materials Credit #1. Concrete s inorganic composition makes it an ideal material to be Coastal Timber Harvesting 3.25 Source: Environmental Council of Concrete Organizations, 2004 ECCO indexed the impact of various materials against concrete to show that iron-ore mining, for example, has 2.25 times the impact on the environment as concrete-aggregate extraction. recycled, and it frequently is crushed and reused as aggregate for road bases or construction fill, says Shepherd. As with the Building Reuse credit, these options are available only in the future after the building has been constructed and is being reconsidered for other uses. But concrete s impact on these points for future use play a role in specifications made today. An all-precast parking structure serves the Arizona Department of Environmental Quality office building, which has received LEED certification. One of the factors in its certification was that the precaster, TPAC of Phoenix, was in close proximity to the project site, which saved transportation costs and fuel for transportation.

4 Precast concrete offers other wastesaving benefits, says VanGeem. Less material is required to produce precast components because precise mix designs and tighter tolerances can be achieved, she says. Less concrete is wasted because quantities of constituent materials are tightly controlled. The waste materials also are more likely to be recycled because concrete production takes place in one location under controlled conditions, she says. For instance, gray water often is recycled into future mixes, between 5 and 20 percent of aggregate in a mix can consist of recycled concrete and sand used in finishing are reused. Steel forms and other materials used in casting also are reused. There also is less dust and waste at the construction site, because only the needed precast components are delivered, she notes. And there is no debris from formwork and associated fasteners. Fewer trucks and less time are needed because concrete is made offsite. That s particularly beneficial in The six-story Arizona Department of Environmental Quality office building, which is LEED certified, features a precast concrete façade skin and an adjacent total-precast parking structure. The components were produced by TPAC of Phoenix, located within five miles of the project. urban areas where minimizing traffic disruptions is critical. Less noise is produced at the site as well, reducing noise pollution. A properly designed precast concrete system will result in smaller structural members, longer spans and less material used on-site, VanGeem says. This translates directly into economic savings. It also results in environmental savings. Using less material means using fewer A precast concrete system will result in smaller structural members, longer spans and less material used on-site. natural resources and less manufacturing and transportation energy not to mention the avoided emissions from mining, processing and transporting raw and finished materials. Recycled Content (Materials Credit #4). This two-point credit is received for using materials with post-consumer recycled or post-industrial recycled content of a specific total. Precast concrete components contribute to this requirement because supplementary cementitious materials can replace a proportion of cement in the mix, and those materials are considered postindustrial recycled ingredients, explains Shepherd. The use of these materials is growing, and they will grow in use as more designers learn about the options and the benefits. The key reason the supplements aid concrete s environmental friendliness derives from the Portland cement, which makes up 7 to 15 percent of the total volume of a precast component, VanGeem estimates. It is a manufactured product and uses energy during production, although the industry has reduced energy usage per ton of cement by 35 percent since 1972, she notes. (Water comprises 14 to 21 percent of precast concrete s volume, while aggregate accounts for the rest.) The most common supplementary cementitious materials are fly ash, silica fume and slag cement. Fly ash is the residue remaining from fossil-fuel power plants; silica fume is the by-product from the electric-arc furnace used in the production of silicon or ferrosilicon alloys; slag cement is created from iron blast-furnace slag. All of the waste products would end up in landfill if not reused. Recycled concrete also can be used in new precast components as aggregate, VanGeem notes. In many 21

5 22 Insulated sandwich wall panels, in which insulation is placed between two wythes of concrete, add energy efficiency to a precast architectural wall panel s natural benefit of high thermal mass. cases, the use of fly ash and other supplementary materials can produce a more durable product than a totalcement mix can provide. Flad & Associates long has been a proponent of the use of fly ash and other supplementary materials, says Maine. We typically use concrete with 15 to 20 percent fly ash. We believe we get a superior product by using fly ash while also reducing the cement content. Recently, we ve begun specifying ternary The goal should be to optimize the use of fly ash, not maximize it. mixes with portland-cement of 40 percent. The company uses this approach in most of its precast concrete buildings, whether they are trying to achieve LEED certification or not, he notes. We have rewritten our specs to be LEED compliant and provide a baseline for green building in every way we can, he says. There are greater and greater applications for its use. Clearly, some products are truly green, but many others can be made to be green or can be used in ways that make them green. type of supplement, he notes. The reactivity of fly ash with the other materials can vary by coal seam and the electrical-generating plant from which it was obtained. The best approach is to talk with the producer in advance and avoid prescribing an amount of fly ash beforehand, Shepherd says. Tell the producer to use the maximum amount that s effective and give him a performance standard for the application, not just a percentage. The goal for long-term performance of a building will optimize the use of fly ash, not maximize it. Local/Regional Materials (Materials Credit #5). This one-point credit is offered when at least 20 percent of building materials are manufactured within a 500-mile radius of the site. An additional point is offered when half of the regionally manufactured products are extracted or recovered within 500 miles. Precast concrete meets both of these requirements in virtually all cases, VanGeem says. Most precast plants are within 200 miles of the project, and the raw materials used to produce the precast concrete components cement, aggregate and rebar usually are Most precast concrete plants are located within 200 miles of the projects for which they supply materials, easily meeting the LEED requirement for proximity. obtained from sources within 200 miles of the precast plant, she estimates. This advantage leads many designers to replace granite, stone and other By using precast concrete rather than marble or granite, we didn t have to ship the products. imported products with precast concrete panels. The local proximity was a key reason Leo A. Daly chose the material for the National Park Service headquarters, says Morgan. By using precast concrete rather than marble or granite, we didn t have to ship the products. That saved both significant shipping costs, as well as adding environmental friendliness. Opus Architects & Engineers used this credit to help achieve LEED certification for one of its recent projects, the six-story, 30,000-square-foot Arizona Department of Environmental Quality office building in Phoenix. The building is clad in precast concrete panels, as is its companion building, the Arizona Department of Administration, and both have adjacent parking structures featuring total-precast concrete structural systems. The precast materials were supplied by TPAC in Phoenix, less than five miles from the project. Both buildings were designed with the same environmental characteristics, according to Alan Torvie, senior director of construction at Opus West, but only the first was submitted for certification. Additionally, precast is recognized as a benign material, meaning it is non-toxic, Too Much Fly Ash? Some designers try to push the potential too far in their zeal to achieve more, warns PCA s Shepherd. Architects are clamoring to put in as much fly ash as they can, without understanding the chemistry and ramifications involved, he says. There are several decades of research supporting the performance benefits of reasonable quantities of fly ash. Even before sustainability s influence, the concrete industry used about 9 million tons of fly ash annually to achieve better durability. The optimum amount of supplementary materials varies by type of cement and Fisher Pavilion on the Seattle Center campus in Seattle hosts cultural festivals and a variety of events. The 19,700-square-foot rooftop plaza overlooks the center s two acres of landscaped green space and features 22 thin-flanged double tees. Balconies consist of 8- and 12-inch hollowcore slabs, with precast inverted tee and L beams used as the support structure. The design, which achieved Silver LEED Certification, was created by The Miller Hull Partnership, with precast components supplied by Concrete Technology Corp. in Tacoma, Wash.

6 LEED POINTS AVAILABLE TO PRECAST CONCRETE PROJECTS Category Type Possible Points Energy & Atmosphere Prerequisite #2 Minimum Energy Performance Required Credit 6.1 Optimize Energy Performance, 15 to 60% 2-10 Materials & Resources* Credit 1.1 Building Reuse, Maintain 75% of Existing Shell 1 Credit 1.2 Building Reuse, Maintain 100% of Existing Shell 1 Credit 2.1 Construction Waste Management, Divert 50% 1 Credit 2.2 Construction Waste Management, Divert 75% 1 Credit 4.1 Recycled Content, Use 5% Post-Consumer or 10% Other 1 Credit 4.2 Recycled Content, Use 10% Post-Consumer or 20% Other 1 Credit 5.1 Local/Regional Materials, 20% Manufactured Locally 1 Credit 5.2 Innovation & Design Credit 1 Local/Regional Materials, 50% Harvest Locally (or 20% Manufactured Locally, as required in Credit 5.1) Innovation in Design, Use of High-Volume Supplementary Cementitious Materials 1 up to 4 Credit 2 LEED Accredited Professional 1 Project Totals 23 * In some cases either Credit 1 or Credit 2 will be used but not both. Scoring: Certified: points Silver: points Source: Environmental Council of Concrete Organizations (ECCO) Gold: points plus 2/5/03 Credit Interpretation Request to LEED Platinum: points and has excellent durability, although projects don t receive credit for these characteristics, Torvie says. Innovation in Design (Innovation and Design Process). Up to four points can be awarded for innovative green design strategies that do not fit into existing LEED categories. For instance, Shepherd notes, an innovation credit has been given in projects for using concrete that has a supplementary-material content of 40 percent, if proper testing for compatibility has been done. An additional point is available for using LEED-certified professionals on the team. The LEED-professionals point was easy to achieve for the National Parks project, as seven individuals on the construction team are accredited, including personnel with the developer, architect, contractor and mechanical engineer. The project has received an additional point because the building will be used as a teaching tool for sustainability and environmental friendliness. National Park Service employees will teach visitors about the building s design, its choice of building material and its decreased impact on the environment. Precast concrete s role in the building will be part of those lessons, Vox Populi Are you discussing LEED certification more with your customers? Who is initiating the conversation? What information or what tools can the precast industry provide to help you in specifying materials? Share your thoughts with us at: helping to spread the word about the material s benefits to the environment. pci.org Craig A. Shutt Click For More For additional material on the use of precast concrete in LEED projects, visit knowledgebank/leed04.pdf. (Adobe Acrobat version 4 or greater required.) To learn more about energysaving techniques, visit the Designer s Knowledge Bank by clicking on the DKB icon at www. pci.org or at your local precaster s Web site. 23

7 ASCENT CASE STUDY Pharmacia s Building Q

8 The Midwest Regional Office of the National Park Service West Elevation North Elevation CASE STUDY ASCENT South Elevation

9 ASCENT CASE STUDY Fisher Pavilion