Metal Roof Retrofits: Maximizing Energy Efficiency

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Metal Roof Retrofits: Maximizing Energy Efficiency

Metal roofing has long been praised for its durability, sustainability, and versatility. However, the real advantages of metal roofs come into focus when considering energy efficiency and cost savings through strategic retrofitting. Metal roof retrofits offer a wealth of opportunities to enhance a building’s thermal performance, reduce greenhouse gas emissions, and deliver lasting financial benefits.

Roof Structure Considerations

Before diving into the energy efficiency gains, it’s essential to thoroughly assess the existing roof system. Design professionals and contractors must first identify the type of roof structure, spacing of secondary members, deck material, insulation thickness, and condition of the weathering membrane. This lays the foundation for determining the appropriate retrofit strategy.

Mark James, president of RetroSpec LLC in Dallas, emphasizes that “the existing roof support system controls everything in the new framing’s base member type and the placement of the vertical members to support new roof purlins.” Proper anchorage is also critical to prevent wind uplift from tearing the new roof off the existing one. Furthermore, the wind uplift performance should be updated to comply with current building code requirements.

Energy Efficiency Strategies

With a solid understanding of the existing roof conditions, designers can then explore a range of energy efficiency upgrades. Insulation levels, for example, are often woefully inadequate in older buildings, with typical values ranging from R-6 to R-13. By adding rigid insulation boards or fiberglass batts over the existing roof, the building’s thermal performance can be significantly improved, aligning with modern ASHRAE 90.1 recommendations of R-26 to R-38.

Another highly effective technique is above-sheathing ventilation (ASV). Research by the Metal Construction Association (MCA) and the U.S. Department of Energy’s Oak Ridge Building Envelope Technologies Laboratories has shown that ASV can decrease heat gain through the roof assembly by 30% in the summer and reduce heat loss in the winter. When combined with cool roofing membranes, these savings can reach up to 45% during the summer months.

When undertaking a metal-over-sloped or metal-over-metal retrofit, the cavity between the existing and new roof offers an ideal opportunity to incorporate solar heat recovery systems. Similar to ASV, instead of venting the hot air out, the radiant-heated air can be captured and used to heat the building, qualifying for federal solar energy tax credits.

Cost-Effective Retrofitting

While the upfront costs of a metal roof retrofit may seem daunting, the long-term savings and financial incentives make it a worthwhile investment. Andy Feth, project director at C.W. Driver Companies in San Diego, notes that metal roofs typically have a much longer service life than shingles, built-up roofing, or single-ply systems. This reduces the frequency of roof replacements and the associated waste sent to landfills.

Additionally, metal roofs can be eligible for a variety of federal, state, and local incentives, including solar energy tax credits, accelerated depreciation schedules, and utility rebates. According to the MCA, a standing seam metal roof with a photovoltaic (PV) system can currently qualify for a 30% federal tax credit on the entire system cost, along with other incentives.

When combined with the energy efficiency gains from improved insulation, ventilation, and solar heat recovery, MCA reports savings of $1 or more per square foot, translating to a three- to five-year return on investment.

Aesthetic Enhancements

While functionality and energy efficiency are the primary drivers, metal roof retrofits also offer ample opportunities to enhance the aesthetic appeal of a building. Metal can be bent and shaped to fit the existing structure, allowing the new roof to seamlessly integrate with the overall design.

For example, the Welcome Pavilion at Hershey Gardens in Hershey, Pennsylvania, features a curved metal standing seam roof that mimics early 20th-century design and seamlessly crowns the conservatory. Similarly, the University of Arkansas Champions Hall in Fayetteville showcased metal’s durability, sustainability, and optimal building enclosure attributes, making it the clear façade choice.

Practical Applications

A notable example of a successful metal roof retrofit is the case of Goodfellow Air Force Base in San Angelo, Texas. As part of the U.S. Department of Defense’s mandate to increase renewable energy sources and reduce energy consumption, the base received a highly sustainable 11,900-square-foot metal roof upgrade.

The retrofit included the integration of photovoltaics, boosted insulation levels, a solar thermal system, and a 10,000-gallon rainwater collection cistern. Utilizing data from a U.S. Department of Energy Oak Ridge National Laboratory-installed system, the project team was able to establish a baseline energy usage and then tailor the retrofit to maximize energy savings and electricity generation.

This unique approach of integrating the energy-saving technologies directly into the roof system, rather than treating them as standalone additions, allowed the Goodfellow project to maximize its impact on the building’s overall performance. The solar thermal system, for instance, is positioned within the roof cavity to optimize energy generation for domestic hot water and space heating, generating more than 750,000 KBTU of energy per year and saving $11,750 in annual energy costs.

Conclusion

Metal roof retrofits present a compelling opportunity to transform the energy efficiency and aesthetic appeal of existing buildings. By carefully assessing the existing roof structure, implementing strategic insulation and ventilation upgrades, and seamlessly integrating renewable energy technologies, building owners can unlock substantial long-term savings and environmental benefits.

Whether it’s the exceptional durability, the compatibility with solar systems, or the energy-efficient cool roofing properties, metal roofs stand out as a sustainable choice for commercial and residential properties alike. As the industry continues to innovate, the potential for metal roof retrofits to enhance building performance and reduce operational costs will only grow more compelling.

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