Seven tips for mounting solar on asphalt shingle roofs

Solar Power World recently hosted a webinar with roof-mounting experts from EcoFasten Solar, IronRidge and SunModo. The speakers shared many best practices for mounting and experiences from the field. Below are tips offered for asphalt shingle roofs by Dan Felix, training manager at IronRidge. View the whole webinar here, or read tips for metals roofs or tile roofs.

1. Check with roofing manufacturers about flashing. IBC 1503-2 states that flashing shall be installed to prevent moisture entering from penetrations through the roof plane. IBC 1507-2-9 says flashing shall be applied in accordance with this section of the code and also the asphalt shingle manufacturer’s printed instructions. “From that note, it’s clear that an installing contractor should identify the exact manufacturer of the roofing material on a customer’s home and double-check the manufacturer’s website for instructions on properly installing a flashing, both for maintaining the warranty and ensuring a waterproof roofing system,” Felix said.

2. Use quality flashing. “There’s now just a huge amount of flashings options from which to choose in the solar industry,” Felix said. “We should be paying notice to a few key items.” Among them are corrosion resistance, structural performance, waterproofing and ease of installation. A flashing should be guaranteed to last the life of a solar system. Felix recommends a product with an elevated platform for the actual penetration location to divert water. Extra wide flashing can accommodate any errors when locating the rafter. Flashing manufacturers should be able to provide installers with third-party certifications of their products.

3. Consider shingle thickness. Shingles with 15- and 20-year warranties are relatively thin and present few issues when installing flashings. Shingles with longer lifespans, however, are thicker and have a layout design with high and low points. Flashing with elevated attachment points will work well in the low areas of the shingle layout, minimizing the chances of the flashing curling as it’s tightened (casually known as the “potato chip effect”). In high points, extra wide flashing will keep wind-driven rain from getting to the elevated section of that roofing material where a penetration is located.

4. Use the right sealant. When applying sealant into a pilot hole, contractors need to use the sealant specified by the roofing manufacturer to maintain warranties. This information, and much more, can be found on manufacturers’ websites.

5. Beware of the drip edge in the course of shingles. Make sure the flashing does not extend beyond the drip edge of the shingle as the space underneath could allow leaves and debris to accumulate, causing rot and mildew. Install flashing so that its bottom edge aligns with the drip edge of that course of shingles.

6. Don’t disrupt water diversion. Manufacturers will often allow flashing to be installed a little further into a course of shingles than normal, if needed. But if a flashing product has an elevated platform for attachment, be sure to trim the shingles around the elevation so that it sits flush with the base of the flashing. “You don’t want to send water to the top of the platform,” Felix said. “That platform is designed into the product to divert water away from your penetration location.”

7. Avoid removing nails from shingles. IBC 1507-2-7 states that asphalt shingles shall have the minimum number of fasteners required by the manufacturer. “You’ll find that there are some flashing manufacturers that recommend removing nails or fasteners in the way of your installation,” Felix said. “As an installer, I don’t recommend that.” Roofing installers typically use the minimum number of nails required. Felix recommends rocking the flashing back and forth against the nail to determine the horizontal location of the nail.  Then taking a pair of tin snips, carefully cut the smallest V-notch necessary in the flashing to place it properly into the course of shingles.