Choose a metal roof for your residential solar panel mounting system

Choose a metal roof for your residential solar panel mounting system

More and more homeowners are choosing to add solar power to their high-performance homes, but they may overlook an important factor: the roof under the solar panels.

U.S. homeowners are warming up to the value of solar or photovoltaic (PV) power. In fact, the third quarter of 2013 marked the largest quarter ever for residential PV installation, according to a new study from GTM Research and the Solar Energy Industries Association.

In total, the U.S. installed 930 megawatts of PV in the third quarter of 2013, up 35 percent year-over-year, and a 20 percent jump from the second quarter of 2013. These total figures represent the second largest quarter ever for the U.S. solar market.

Solar power is often a key element of energy efficient homes, such as those striving to meet net-zero or Passive House standards. Solar panels, along with a tight thermal envelope and insulation among other strategies, help a home produce more energy than it consumes.

A solar power system can really pay off. Builders who install solar electric systems in their California housing developments estimate that a 2.4- kilowatt system will offset 40 percent to 50 percent of the electricity needs of an energy-efficient home. That number could be lower or higher depending on the amount of sunlight (regardless of climate) your home receives each year and the energy efficiency of your home.

The energy can offset your utility bills by a large amount. If the system generates more electricity than your home uses, for instance when you’re on vacation during the sunny summer months, then it feeds power into the grid instead.

Your utility company, in all but a few states, will pay you for this net-excess generation (NEG) electricity it gets by giving you credits on your next electric bill. This process is called net metering. And solar power can pay off when it’s time to sell your home. According to the Appraisal Journal, a solar electric system increases your home's value by $20 for every $1 in annual utility bill savings, which means a system could almost pay for itself with the appraisal value increase in some cases.

Solar panel roof mount options

Most solar systems are mounted on the roof of the home. One of the factors to consider in a solar installation is what type of roofing material will under those solar panels. The typical crystalline solar panels are glass and metal rectangular modules that are mounted on racks connected to the roof.

Those modules and racks must withstand extreme weather conditions such as high winds, snow and rain. If you’re considering installing solar panels on the roof, you will want to ensure that the roof is in good shape and even consider installing a new roof.

The useful life of solar modules is 20-25 years, so experts recommend a roof surface that will last at least as long as the solar modules. It can be very expensive to dismount and remount the solar panels and the mounting racks to replace the roof.

Although asphalt and composition shingles are probably the most common form of roof in the U.S., they are one of the worst options for solar panel installation. In most cases, the warranty life of the asphalt roof does not equal the life of the solar panels so it’s likely the roof will have to be replaced. Also, common mounting racks require penetrations through the asphalt shingles to reach the roofing structural members below. Those penetrations could lead to leaks and other roof problems and will most likely void the warranty from the roofer and shingle manufacturer.

One of the most popular options for solar panel installation is a standing seam metal roof. In a standing seam roof, the panels are connected at seams that rise above of the level of the metal roofing. The seams is raised, or standing, as opposed to flush mounted. The fasteners are concealed so there is only a smooth ridge extending from top to bottom so there are no seams running horizontally across the roof. Roof panels are usually made of Galvalume-coated steel or aluminum. The panels are pre- formed at the factory and are very durable.

Solar panels racks offer the option of fasteners that lock on to the standing seams. That means there are no roof penetrations that would lead to leaks or premature wear. The roof metal roof panels provide a sturdy base that will outlast the life of a typical solar system. For instance, the warranty on standing seam metal roof panels from Metal Sales is 45 years.

Another option for roof-mounted solar is thin-film solar PV laminates. Although these panels are much lighter and thinner than crystalline-based panels, they don’t produce as much electricity either. Some panels are adhesive-backed and can be simply stuck to a metal roof. Some types also use a racking system that’s much lighter duty than the ones used for crystalline solar modules but mount easily to standing seam metal roofing.

Benefits of metal roofing

In addition to being a highly desirable platform for solar panels, metal roofing offers a number of benefits for the homeowner.

Durable: Metal roofs offer a service life of 30 to 50 years depending on materials and finishes. The return on investment of a metal roof is high because of the longevity. A less expensive type of roof might have to be replaced two or three times in the life span of a single metal roof.

Energy efficient: Metal roofs help reduce heating and cooling loads because of the high reflectivity and low emissivity of solar radiation of the roof. Many roofs qualify for the Energy Star Cool Roof program, which reflects more solar heat and are offered in a wide variety of colors to suite any architectural style. Highly reflective roofs help keep rooftop temperatures low for better performance from solar panels.

In addition to rooftop solar photovoltaic panels, metal roofs integrate solar thermal water heating panels, as well as wind turbine applications.

Green certification: Metal roofing can help a home meet the requirements for green certifications, such as LEED for Homes from the USGBC, Energy Star and the National Association of Homebuilder's Home Innovation National Green Building Standard.

Life-cycle impact: Metal roofs are made with a high quantity of recycled metal, and are completely recyclable at the end of their useful life.

If you’re considering a residential solar power system, first start with your roof. Your choice of roofing will play a key role in the successful installation and operation of your system. A metal roof will help reduce your costs and give your solar power system the best chance for success.

Read more about roofing.


Topics: Photovoltaic / Solar Panels, Roofing, Solar Power


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