Case in Point

As part of the U.S. Department of Defense’s (DOD) mandate to produce or procure 25 percent of all DOD building energy from renewable sources by 2025, reduce energy use by 30 percent by 2015, and another 37.5 percent by 2020, San Angelo, Texas’ Goodfellow Air Force Base received a new metal roof integrated with energy-efficient technologies.

Photo courtesy of Paramount Metal Systems LLC

Utilizing data gathered from a U.S. Department of Energy Oak Ridge National Laboratory-installed data acquisition system to monitor San Angelo, Texas’ Goodfellow Air Force Base’s temperature and heat information, a highly sustainable 11,900-foot metal roof retrofit with photovoltaics, boosted insulation levels, a solar thermal system, and rainwater collection was installed.

After gathering key building energy performance data and utility billing information, the former collected from a DOE ORNL-installed data acquisition system to monitor the building’s temperature and heat information, a baseline energy usage was established.

A highly sustainable 11,900-foot metal roof retrofit with photovoltaics, boosted insulation levels, a solar thermal system, and rainwater collection was then executed. While many reroofing projects have incorporated such technologies, the Goodfellow AFB was unique in that the energy-saving technologies were integrated into the new roof to form the building envelope.

Essentially, the roofing system components were integrated into one retrofit system to maximize electricity generation and minimize the building’s cooling load. For example. the solar-thermal technology sits inside the roof cavity to optimize energy generated for domestic hot water and space heating. The system is anticipated to generate more than 750,000 KBTU of energy per year and save $11,750 in annual energy costs.

Furthermore, a 10,000-gallon cistern captures approximately 131,000 gallons of potable water for irrigation.

In the process of installing these integrated technologies, first, structural purlins were installed over the existing metal roof. Next, additional insulation in the form of rigid insulation board was placed over the existing roof, and a waterproof roof underlayment was applied over the insulation. After that, a radiant barrier was installed over the underlayment, and then the integrated solar-thermal system was installed over the radiant barrier to optimize heat transfer.

In addition, a thermal purlin is used to position the solar thermal system tubing and configured to support above-sheathing ventilation to take place from the eave to the ridge.

Finally, 24-gauge standing-seam metal roofing panels, prepainted with a polyvinylidene fluoride cool coating, were laminated with a thin-film PV system and installed directly over the solar-thermal system.

Best Practices

Sharing a few best practices for retrofitting metal-over-flat and metal-over-sloped roofs, Mark James, president of RetroSpec LLC in Dallas, emphasizes that first and foremost, the existing roof support system must be identified. This includes the type of system, spacing of secondary members, decking type, insulation thickness, and weathering membrane.

“Once this is completed, then the design of a new light-gauge structural framing system can be determined and estimated,” he explains. “Design professionals and contractors must understand that the existing roof support system controls everything in the new framing’s base member type and that the placement of the vertical members will support new roof purlins. The new roof purlin spacing is controlled by the new metal roof system’s tested values for wind uplift and gravity load.”

Proper anchorage is also key in order to prevent wind uplift from tearing the new roof off of the existing roof. Furthermore, wind uplift performance should be updated to comply with the current building code requirements.

For metal over flat, the added weight of a sloped build-up retrofit system is 2 to 5 pounds per square foot (PSF), and for metal over sloped, it’s 1.5 to 2 PSF. The structure should be tested with a series of concentrated loads as opposed to uniform loads.

“A critical factor is ensuring a good sound substrate on which the new roof can be installed,” adds Feth. “In addition, all penetrations, changes in plane, and transitions to other building elements must be detailed/sealed properly. Each manufacturer will have their own suggested details for various conditions.”

Choosing Metal

Whether it’s metal’s exceptional longevity, durability, recyclability, compatibility with solar technologies, or the energy efficiencies delivered by metal roof retrofits, metal walls and rooms are an excellent sustainable choice for today’s commercial buildings.

SUSTAINABLE METAL DESIGN BY THE BOOK

Awarded a 2017 Metal Architecture’s Sustainable Design Award, the Swift Lee Office-designed Twin Rivers Charter School in Yuva City, California, features insulated metal panels with light-gauge metal framing and batt insulation, perforated aluminum sunscreen panels on Z-shaped frames for solar shading on three exposures, and perforated metal curtains to diffuse direct sunlight.

Photos courtesy of Swift Lee Office

At Twin Rivers Charter School in Yuva City, California, insulated metal panels with light-gauge metal framing and batt insulation, perforated aluminum sunscreen panels on Z-shaped frames for solar shading on three exposures, and perforated metal curtains to diffuse direct sunlight earned Swift Lee Office a 2017 Metal Architecture’s Sustainable Design Award.

For the two-building complex—a 28,500-square-foot K-5 building with a media library, and a 21,500-square-foot building with grades six through eight classrooms and a gymnasium—the use of metal building systems offered multiple advantages.

For starters, by selecting preengineered systems and components that are designed to work together, this created flexible energy-efficient structures capable of accommodating a wide range of use, explains Swift Lee Office Principal Gloria Lee, Pasadena, California.

Furthermore, future renovations will be less costly than working with conventional construction.

“With the metal building system, it’s all very integral at the building component and structural levels,” Lee explains. “Whether it’s the tall gymnasium with the classrooms or lunch shelter with the admin and classrooms, we were able to create it with one building system.”

Because the IMPs, for example, delivered a complete water- and air-resistant building enclosure with a high level of thermal performance, it was easier to add additional sustainable elements, such as skylights, clerestory windows, light scoops, and displacement ventilation.

“You’re not building curbs, and you’re not dealing with flashing issues and details,” she explains. “The details are made to go together, so it’s very quick and easy construction, and highly waterproofed.”

In selecting metal building systems, it was the architect’s intent to expose the metal architecture, thereby creating hands-on learning experiences about how the technology works.

In the grand scheme of things, Lee states that sustainability is much more than a checklist. “I think sustainability has to be thought about more broadly, not just about getting LEED points or using recycled material. But really about holistically seeing how sustainable it is to provide a learning environment for children who we want to grow up to be stewards of our planet.”

AWARD-WINNING METAL PANEL SYSTEM DESIGN

When Sherwood Middle School in Shrewsbury, Massachusetts, needed a new building, the project coordinators embraced the metal panel exterior presented by architects Lamoureux Pagano & Associates.

Photos © Travis Blake

A well-designed composite metal panel system and a ribbed profile panel system earned Lamoureux Pagano & Associates an MCA Chairman’s Award for Sherwood Middle School, Shrewsbury, Massachusetts, new facility.

The building’s all-metal facade combines various substrate sand rainscreen panels, including a composite metal panel system and a ribbed profile panel system, winning the MCA Chairman’s Award of 2013 for primary and secondary education facilities. The paneling is a steel and aluminum blend, presenting an aesthetic facade and a high R-value at a reasonable cost.

“One of the things that the community wanted was a very energy-efficient building,” explains Kathryn Crocket, vice president, Lamoureux Pagano & Associates, Worcester, Massachusetts. “[Metal] gave us some flexibility in terms of modulating the aesthetic of the exterior of the building and giving a futuristic look to the building, which was very appealing to all.”

Crockett and her team designed a 130,000-square-foot building that insulates the interior well against the temperature swings that are typical of the Boston area. Another green feature is the southern exterior gym wall where a perforated metal panel system features a low-tech solar wall. The system gathers warm air, then a fan system pulls it inside, helping to heat the gym.

Thanks to superior insulation levels, temperatures inside the building take a long time to drop, even when it’s well below freezing outside. “At the end of the day, the building holds its heat,” says Robert Cox, superintendent of public buildings for the town of Shrewsbury. “These are sheathing panels. And it’s all in one piece. That’s it. You put it up, and it’s sealed. It’s tight. It’s done.”

That’s an added advantage in public buildings, he explains, where operating money is hard to come by. “So when we do a capital project, we try not to skimp,” he says. “We try to make it a building that’s substantial, one that’s going to last.”

Now that the school’s staff and 1,000 students have been occupying the building, the overall response to it has been very positive. “People are very excited about it,” Crockett says. She notes that the school was designed and built to last for decades to come. “They were looking for a progressive school,” she says. “They have extremely high standards for their curriculum, and they wanted a school that reflected that, and that would give them flexibility for 50 years.”

End Notes

¹Kazlov, Paul. “Metal Roofing: An Unlikely Way to Reduce Waste and Save Energy.” Triple Pundit. 6 August 2014. Web. 30 August 2017. www.triplepundit.com/2014/08/metal-roofing-unlikely-way-reduce-waste-save-energy

²Government Product News Staff. “Expert: Metal buildings offer versatility to governments.” American City & Country. 14 April 2015. Web. 30 August 2017. www.mbma.com/media/American%20City%20and%20County%20Reprint.pdf

³Deffenbaugh, Paul. “31^st Annual Architect’s Survey.” Metal Architecture. March 2017. Web. 30 August 2017. www.metalarchitecture.com/articles/magazine-features/31st-annual-architect-survey.aspx

⁴Walter P. Moore and Associates. “Athena Impact Estimator Case Studies.” August 2015. Web 30 August 2017. www.mbma.com/media/WalterPMooreAthenaImpactorCaseStudies-MBMA_Aug2015.pdf

⁵“ASMI accepts MCA report on increased service life of metal roofing.” Construction Magazine Network. 26 August 2015. Web. 30 August 2017. www.constructionmagnet.com/metal-roofing-magazine/asmi-accepts-mca-report-on-increased-service-life-of-metal-roofing

⁶“Metal Roofs and Walls: Promoting the Future of ‘Green’ and Sustaining the Environment.” BOMA International. 2006. Web. 30 August 2017. www.boma.org/research/Documents/Find%20a%20Resource/Metal.pdf

⁷Konopacki, S. and Akbari, H. “Measured Energy Savings and Demand Reduction from a Reflective Roof Membrane on a Large Retail Store in Austin.” Lawrence Berkeley National Laboratory. January 2001. Web. 30 August 2017. www.vinylroofs.org/wp-content/uploads/2011/06/LBNL_study-1.pdf

⁸“Guidelines for Selecting Cool Roofs.” U.S. Department of Energy Building Technologies Program. July 2010. Web. 30 August 2017. heatisland.lbl.gov/sites/all/files/coolroofguide_0.pdf

⁹Taha, Haider and Akbari, Hashem. “Cool Roofs as an Energy Conservation Measure for Federal Buildings.” Lawrence Berkeley National Laboratory. April 2003. Web. 30 August 2017. pubarchive.lbl.gov/islandora/object/ir%3A120601/datastream/PDF/download/citation.pdf

¹⁰Casey, Tina. “What Color is Your Parking Lot: New Research Combats Heat Island Effect.” Triple Pundit. 17 September 2012. Web. 30 August 2017. www.triplepundit.com/2012/09/heat-island-effect/

¹¹“Retrofit Roofs Offer Design, Environmental, and Financial Benefits in New and Existing Construction.” Metal Construction Association. August 2016. Web. 30 August 2017. www.metalconstruction.org/download.php/education/tech_resources/retrofit/WhitePaper_BenefitsRetrofitRoofing

¹²Haddock, Rob. “Rooftop Equipment Mounting and Penetrations for Low-Slope Standing-Seam Metal Roofs.” Roofing. 3 November 2013. Web. 30 August 2017. www.roofingmagazine.com/author/rob-haddock/

¹³“Retrofit Re-Roofing with Metal Roof Systems.” Metal Construction Association. Web. 30 August 2017. www.metalconstruction.org/index.php/education/educationalresources

The Metal Construction Association brings together a diverse industry for the purpose of expanding the use of metal in construction through marketing, research, technology, and education. MCA member companies gain tremendous benefit from association activities that focus on research, codes and standards, market development, and technical programs. www.metalconstruction.org