Metal Roofs and Solar Energy: An Ideal Match

Everyone is talking about—and doing something about—sustainability. Metal roofs fit nicely into the sustainable-material equation because of their myriad traits, such as recyclability, reflectivity, longevity and durability.  Another major component in the sustainability equation is renewable energy—the production of energy from renewable resources like sun and wind.  A metal roof is the ideal location for solar energy production on homes, commercial buildings and recreational applications.

Why Solar Panels and Metal Roofs?

metal roofing and solar panels
One of the key factors for long-term success of rooftop solar energy is the quality of roof under the solar panels.  Roofs under photovoltaic (PV) systems should be durable and have an equivalent service life to the solar panels.  However, too many traditional roof systems do not have a service life that matches, let alone exceeds, the service life of the PV panels.  This is where metal roofs excel.

Service Life of Metal Roofs

A study of roof system longevity presented at the Fourth International Symposium on Roofing Technology by Carl Cash, a principle at Simpson Gumpertz & Heger, showed that metal panel roofs have the longest service life when compared to asphalt-based roofs and single ply roofs.   The study showed that the average life of metal panels is 25 years.  BUR and EPDM were second and third, respectively, at 16.6 and 14.1 years of average service life.  Exceeding the Cash study, a more recent study conducted by the Metal Construction Association (MCA) and Zinc Aluminum Coaters (ZAC) Association showed the longevity of low-slope unpainted 55% Al-Zn alloy coated steel standing seam roofing (SSR) systems is 60 years.

Service Life of Solar Panels

Solar panels will last 25 to 30 years.  In fact, some of the very first PV panels from the 1960s and 1970s are still producing energy.  While their efficiency might decrease over time, solar panels will make electricity for many decades.  For the most cost-effective rooftop solar energy installation, the longevity of the roof should be equivalent, or greater, than the solar panels so that the roof doesn’t need replacement during the life of the solar energy system.  Metal panels are the most reliable, long-term roofing system for solar energy installation projects.

Built to Last

Solar Metal Roof Panels
Solar Roof Panels on Real Salt Lake City Stadium

Simply put, installing solar energy on rooftops that don’t have an equivalent service life is a mistake, especially for solar projects that cover a large portion of the rooftop.  The cost of decommissioning, removing, and replacing rooftop solar energy can cost 20% to 100% of the original installed cost.  The cost tends to align with the percentage of rooftop covered with solar panels.  Much of the cost to remove and reinstall is labor, but an older solar energy system will likely need some new components—most likely new wiring—when reinstalled, also adding to the cost.

Rooftop solar installations continue to grow year over year.  And with the extension of the federal investment tax credit for five years, expect more solar energy installations on roofs.  Pair solar energy with a metal roof, and you’ve hit a sustainable “home run.”

Learn other ways to implement Net-Zero Energy strategies into your building and learn how MBCI’s products contribute.

Rooftop Solar Energy

Solar panels on metal roof

The “Sustainability begets resilience” blog ended with a nod to rooftop energy production. So, how will you respond when, not if, a building owner asks you about rooftop solar energy? An appropriate and accurate answer is, “The combination of a metal roof and solar energy is a recipe for a long-term, high-performance roof system,” or something like that. The fact is a metal panel roof is an ideal substrate for a solar energy system.

Installation Methods

Solar energy is the broad term for two sub-categories: photovoltaic (PV) systems (electricity) and solar thermal (hot water) systems. Besides the obvious differences, the rooftop attachment concepts for both systems are quite similar. PV panels and solar thermal panels are commonly rigid with metal frames. Attachment to metal roofing panels can be direct or include rails. Both methods use a customized clip that attaches to the metal roofing panel seam; then, metal-framed PV panels or rails are attached. The need for rails (think “purlins”) depends on the seam spacing and layout of the roof panels relative to the size and layout of the PV or solar thermal panels. Overall roof slope matters, too. Directly attached solar energy systems match the slope of the roof, which is not necessarily the optimum slope for energy production.

Structural & Performance Requirements

Other considerations include the structural load, fire resistance, wind resistance and the use of code-approved materials and components. A solar energy system adds weight to the roof. Does the structure need updating to carry the gravity load as well as any increased wind uplift loads? Adding panels to the roof will increase the sliding load (i.e., drag load) on the clips holding the roof panels to the substructure. And let’s not forget about the potential for snow retention or increased snowdrifts that will add weight.

Fire and wind resistance should be discussed with the manufacturer or designer of the PV or solar thermal system. Fire and wind design are incredibly important, and there are very specific code requirements to meet.

Layout Considerations

Rooftop layout of solar systems, especially PV, should not block drainage or impede roof maintenance. Also, clearance at roof perimeters and access to critical roof areas (e.g., drains, rooftop units) is necessary. Last but certainly not least, check with the metal panel roof system manufacturer about warranty issues regarding a rooftop solar energy installation.

While there are many things to consider when installing solar energy systems on roofs, the long service life of metal panels and the ease of installation certainly make metal roofs and solar energy a great combination!

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