Without flashing, a residential roof with solar might become a leaky mess. When holes are made in a roof—for vent pipes or solar mounts—flashing is the material used to stop water from leaking into the roof. The most common type of flashing is made of aluminum, but there have been advances in this area of the roofing market, as SolarRoofHook‘s marketing director Samantha Dalton explained during a recent Solar Power World webinar. Below you’ll find more information on the main types of flashing used on asphalt shingle roofs.
Aluminum flashing is the most recognized flashing type. A large square-ish size of aluminum redirects water runoff away from the roof penetration. Aluminum flashing is installed by lifting the shingles and inserting the flashing underneath. It secures to the roof by the weight of the roofing material or by nails.
“Aluminum flashing has been in the industry so long, that many people have used it since they began installing solar,” Dalton said. “Aluminum flashing is malleable and lightweight, [and] is also a low-cost flashing option.”
One drawback of the popular aluminum flashing method is that shingle nails have to be removed, leaving more holes in the roof. And if the flashing has to be nailed down, that makes even more holes. Although lightweight, the large size of aluminum flashing pieces can be bulky to ship and handle.
Galvanized flashing uses galvanized steel, making it more rigid than aluminum flashing. Galvanized flashing also redirects water runoff away from roof penetrations and is installed under roof shingles.
“Because of its rigidity, galvanized flashing improved upon the issue aluminum flashing imposed in high wind areas. It won’t bend or misshape in the wind,” Dalton said. “Installers won’t have to worry about keeping it secure at all times while handling it on the roof in order to keep it from blowing away.”
Galvanized has similar problems to aluminum flashing—more penetrations—and is heavier to transport up onto the roof. It’s also more expensive than aluminum flashing.
Rubber/EPDM flashing works alongside a piece of aluminum flashing. A rubber bushing is inserted into the opening of an aluminum flashing where the roof penetration is made. The rubber helps seal the mount from water leaks. Rubber flashing is still installed under shingles and is nailed to the roof.
“Rubber bushed flashing provides a truly watertight seal and does not depend on redirecting water to keep the penetration from leaking,” Dalton said. “However, it still has many of the same downsides as aluminum and galvanized flashing. Rubber bushed flashing is one of the most expensive flashing options in the industry. The flashing is still bulky. Extra penetrations are still made in the roof.”
Elevated flashing is made of aluminum but features a raised section above the roof penetration, preventing water from running directly over the hole. Shingles are still lifted, and the flashing is nailed to the roof.
“Elevated flashing is more water resistant than traditional aluminum flashing. The raised area provides an extra defense against allowing leaks,” Dalton said.
Like rubber flashing, elevated flashing is more expensive because of the improved modifications.
Microflashing, which SolarRoofHook uses with its QuickBOLT product, is much smaller than traditional flashing, at 3 to 4 in. in diameter. A stainless-steel compression washer with EPDM on the bottom is placed directly over the shingle and a bolt is driven into the roof. Solar mounts then connect to that exposed bolt. No shingles are lifted or removed, and the smaller size is easy to ship and assemble.
“Because it compresses and chemically bonds with the roof, Microflashing is able to create a 100% leak proof seal,” Dalton said. “Because Microflashing is not a big, bulky piece of aluminum, the traditionalists of the industry have been hesitant in the past to accept it as a flashing system. However, not only is Microflashing a viable flashing method, it is the most innovative and reliable flashing method available.”
Microflashing is the newest type of flashing to enter the roofing market, and it upends the thought of traditional flashing options.
No matter what flashing type is chosen for a solar project, it’s important to ensure the installation adheres to all appropriate building codes. Often, flashing must be applied in accordance with the asphalt shingle manufacturer’s printed instructions, following best practices from various roofing associations. Choosing the right flashing is an important step, but making sure it’s installed correctly ensures a waterproof solar project.