Stuart and Claudia Wentworth, Quick Mount PV
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With the launch of Quick Mount PV in 2006, Stuart and Claudia Wentworth set in motion a significant and long overdue advancement in code-compliant PV mounting, flashing and waterproofing methods. Previously, Stuart and Claudia had spent 20 years working in the construction trades with a focus on green building and metal fabrication, as well as 7 years installing PV systems in the San Francisco Bay Area. Quick Mount PV currently employs 48 people and recently announced major expansion plans that include an 89,000-square-foot manufacturing facility in Walnut Creek, California. Claudia serves as the company’s CEO and Stuart serves as COO.
SP: Beyond NEC requirements, what codes, standards and regulatory bodies should integrators be aware of, particularly as they relate to roof penetrations?
SW: Many entities have a say about what happens on the roof. Installers, integrators, architects and PV system designers are likely familiar with state and local building codes and standards, but many are less familiar with the code requirements of the National Roofing Contractors Association (NRCA), the Sheet Metal and Air Conditioning Contractors’ National Association (SMACNA), the Asphalt Roofing Manufacturers Association (ARMA) and the Tile Roofing Institute (TRI). Each organization provides guidelines and technical information on roof types and flashing methods. Some guidelines are code-required, some are coderelated, and others would be classified as industry standards or best practices. Roofing manufacturers take industry standards and best practices into play when detailing their products’ installation instructions. Not following these instructions can void the manufacturer’s warranty.
CW: The roofing type, building structure and geographic location are unique to each PV or solar thermal project. In our product-compliance research, we discovered that the most essential task is maintaining the roofing manufacturer’s warranty. For each Quick Mount product, we cross-referenced the most stringent warranty compliance with the roofing industry’s best practices. Our popular Wheel of Accountability (quickmountpv.com/waterproof/code-compliant.html) illustrates all of these relationships.
SP: The US PV industry has been conscious of meeting NEC requirements for decades. To what do you attribute the lag in widespread industry acceptance of code-compliant array flashing and waterproofing?
SW: PV is an electrical product, of course, and the pioneers were more likely electronic geeks than roofing geeks. The considerable safety issues in dealing with the higher dc voltages common in grid-tied PV systems naturally came first. The roofing penetration considerations tend to take a backseat, since any roof-attachment issues become known only after high winds or heavy rains cause problems. As important as the quality of materials and workmanship around the roof penetration are, proper flashing and waterproofing is often more of an afterthought and problems are frequently caught later when insurance companies have gotten involved.
CW: In addition, many kinds of roofs and structures create anomalies on any given installation, which makes it difficult to standardize and teach the correct way to mount something to a roof. All our product designs take many of these building variables into account and seek to minimize the installer’s liability while keeping installation time to a minimum.
SW: Of course, nothing will be quicker than the old L-foot-to-the-roof method—except maybe the demise of the company that did the installation.
SP: What mounting and flashing product characteristics should integrators pay attention to when reviewing available solutions?
SW: One of the most important innovations in our original QBlock family of mounts is our patented elevated water seal. This is accomplished with an internal flute, seamlessly joined to the flashing, which comes up through an attached mounting block. The installation bolt that goes down through this sleeve is then sealed at the top of the flute inside the mounting block, well above the roof surface, where the water runs heavily in a storm. We use a cold weld to bond the flute to the flashing, not the cheaper hot weld that introduces another material subject to electrolysis-caused failure over time.
CW: The flashing and mount should be made of quality materials like aluminum and stainless steel. Does it make sense to use materials with an expected life that’s less than that of the modules they support and the roof they are mounted to? Of course not. The mount should last at least 25 years. Our choice was aluminum since galvanized sheet has a shorter lifespan, even when regularly painted. And it has a tendency to rust, which can cause stains on the roof. We use all-aluminum mounting blocks and flashings in our QBlock line and all-aluminum bases and posts in our QBase products.
SW: Engineering is also very important, as the better the shear and pullout strength, the fewer mounting points of penetration are needed. This results in fewer holes and reduces time and liability. Our mounting method is not only quick on the roof but also saves time in BOS prep off the roof, since our product includes all the exposed hardware. It is stainless steel, and it’s right in the box, so we’re not leaving to chance the quality and physical properties of the mounting hardware used. We use oversize flashing: 12 by 12 inches on our Classic Comp Mount. This enables the flashing to get up into the third course above the drip line and also helps block wind-driven rain from the sides. The same goes for the thickness of the aluminum: We use thick flashing that not only adds life, but also prevents the edges from bending upward when the installation bolt puts pressure on the center of the flashing. This is another water block to prevent wind-driven rain from getting under the flashing.