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Paving Contributes to LEED Platinum Certification

By Lindsay Houts, consultant to Pavestone Company

Verona(TM) Series pavers were used throughout the courtyards of the National Renewable Energy Laboratory. The paver color is Wembly Tan and the pavers in this portion of the project have a Solar Reflective Index of 44. The ornamental trees shown are Thornless Hawthorns. The containers shown at left in the photo are Litter/Recycling/Composting receptacles. Photos courtesy of Pavestone Company

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The challenge was laid out like this: design and build a national showcase building demonstrating the integration of high-performance design features, passive energy strategies and renewable energy as a prototype for the future of large-scale net-zero-energy buildings.

The result was a 222,000 square foot office building that was not only beautiful, but that achieved the highest possible certification of the U.S. Green Buildings Council's Leadership in Energy and Environmental
Design (LEED).

The U.S. Department of Research's Golden, Colo. National Renewable Energy Laboratory (NREL) was built not only to be energy efficient, but to create as much energy as it consumed. This goal, large though it was, did not begin at the doors to the building, but at the entrance to the campus. Everything from paving to plants to walking paths had to be considered. The U.S. Department of Energy selected the Colorado design-build team of Haselden Construction and RNL Design to carry out the construction of a net-zero-energy building.

The smaller chamfers and joints and clean, crisp edges of the pavers complement the project's modern style. The connecting walkway is gray concrete and was part of the project. The narrow paver dimension also gave crews the ability to install solar paver lights in the dining area. The native shrubbery area is covered with recycled wood mulch, which blends into a native grass prairie as the walkway leaves the cafeteria courtyard.

Crewmembers from Continental Hardscape Systems installed pavers that complement the native plants that dot the courtyards. Native and adaptive plants were used in the intimate seating area. Some of the species include Blue Avena Grass (adaptive), Desert Four O'Clock (S. Colo. Native), Pussytoes (native), Rocky Mountain Penstemon (native), Blue Fescue (adaptive).

Green Materials

Everything put into the NREL was either recycled, rapidly renewable, or was regional (from within 500 miles of Golden, Colo.). The Pavestone Co. products that were used in NREL involved all three elements, making them a perfect match for inclusion in the NREL.

RNL Design Associate Brian Nicholson explained the choice of paver manufacturer for inclusion in the NREL project. ''We needed a regional product, and we knew that we liked Pavestone's product,'' he said, noting that having a plant located in Denver made the decision easy.

Paver Selection

In Phase I of the project, Haselden and RNL Design had slated the NREL for 20,000 square feet of the company's Eco-Priora™ permeable pavers and 7,000 square feet of Verona™ Series pavers. The smaller chamfers and joints and clean, crisp edges of the Verona™ Series paver complemented the project's modern style.

As part of the green initiative, the manufacturer's Eco-Priora™ pavers made sense to Haselden and RNL Design immediately. Permeable pavers are common in Colorado, helping to control runoff, mitigate storm surge, and improve water quality overall. The joint profile of this paver lets surface water infiltrate into the pavement and its sublayers. The patented interlocking joint allows surface water to infiltrate thru the joint at flow rates exceeding 100 inches per hour while providing the most stable permeable paver system in the industry. Unlike other open joint systems, the patented ''Priora Joint'' resists lateral and vertical stresses, making this paver an ideal product for parking and driving conditions. The joint is even ADA compliant, ensuring compliance with any additional ADA regulations beyond NREL's net-zero-energy goal.

Installation Hurdles

Before a paver would be able to touch the ground at the NREL many hurdles had to be cleared. In order to make the pavers as energy efficient as possible, even the color of the stone had to be considered. The manufacturer ultimately produced a color specifically for the NREL project, a blend of their limestone and tan hues. The custom color drastically reduced the amount of UV light that would have been reflected off of standard pavers and allowed the NREL to gain additional LEED points. Six separate spray tests were conducted and had to be sent for testing before a paver could be laid.

Designed to be completely pedestrian and bicycle friendly, the Eco-Priora(TM) permeable paver was not only aesthetically pleasing, but also fully functional for the NREL site. Crews used alternating bands of Limestone and Wembly Tan colored pavers separated by concrete bands that define the seating areas.

The 20,000 square feet of permeable pavers used throughout the NREL campus control runoff, mitigate storm surge, and improve water quality. These features contributed to the site's LEED Platinum designation.

Tris Bars, President of Continental Hardscape Systems, and a six-man team were tasked with the installation of the pavers. Because concrete bands broke up much of the space where pavers would lay, the installation did not lend itself to machine-laying. The entire 27,000 sq. feet of pavers were hand laid.

''The work quarters were tight at times, and because of the sensitive nature of the project and the U.S. Government as the client, the biggest obstacle to overcome was ensuring that every person who set foot on the campus had appropriate security clearance,'' Bars said.

Recycled materials were part of the very foundation of the NREL, from the recycled runway materials out of Denver's Stapleton Airport that were used in foundation and slabs to reclaimed steel gas piping used in structural columns, anything that could be substituted with recycled material was.

The paver installation was no different, and recycled concrete was used for the aggregate drainage zone below the permeable pavers, an uncommon but cost-effective, sustainable tactic. Pavestone Denver General Manager Mike Midyett noted that the ''green'' movement is often perceived as overly expensive. In this case, Midyett said, using permeable pavers and recycled concrete in the base was not just ecologically responsible, but helped lower overall project costs by reducing typical storm sewer infrastructure.

Phase II of the NREL project is under construction with a delivery date of November 1, 2011. A new wing will be added to the NREL to provide office space for another 600-700 employees. The courtyards, walkways and roadways will require an additional 45,000 square feet of permeable pavers.

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November 20, 2019, 1:46 pm PDT

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