Solar Roof Talk Episode 7- Wire management for rooftop PV arrays

Back from Solar Power International in Vegas, Jeff and Sue chat with guest speaker Nick Korth, product marketing manager of Renewable Energies for HellermannTyton, to discuss best practices of wire management for rooftop PV arrays. Nick is also host of the “Beyond the Planet” webinar series, which addresses topics such as how weather impacts PV systems.

This week’s topics include:

  • Edge clips vs straps (cable ties)
  • Trunk vs PV cable mgmnt
  • Managing large cable bundles
  • Conduit and roof transition boxes
  • Rail based VS Rail free
  • Metal vs plastic
  • Plastic cable tie life
  • Ratings Hours exposure
  • Codes and Standards language and requirements are modest and lacking in guidance
  • NEC 110.12 neat and workmanship like manner, NEC 300.4 protecting conductors, and NEC 334.3 bend radius
  • UL standards UL 2703 for racking systems, UL 1565 for wire clips, UL 62275 for wire ties
  • Clip Retention of wires, and clip Retention on frame
  • Looping ties through frames
  • Birds, squirrels, and critter management

Subscribe to our podcast on SoundCloud or iTunes and follow it here on the blog!

Solar Roof Talk Episode 3! Rail-based vs Rail-free – Part 2

Quick Mount PV is proud to present Solar Roof Talk, a podcast series for rooftop solar installers and others in the solar industry. Hosted by solar industry veterans, Jeff Spies, Senior Director of Policy & Susan Stark, NABCEP Certified PV Technical Sales Professional™ & Product Specialist.

In this episode, Jeff and Sue continue their discussion of the GTM Research report: U.S. PV Racking 2017: Landscape, Pricing and Forecasts and a comparison of rail-based vs rail-less pv mounting. Topics include:

  • Comparison of rail-based vs rail-less pv systems
  • Module-level electronic attachments
  • Residential and commercial racking and mounting markets
  • Surprise conclusions from the report

Listen to Part 1 here.

Subscribe to our podcast on SoundCloud or iTunes and follow it here on the blog!

Solar Roof Talk Episode 2! Rail-based vs Rail-free – Part 1

Quick Mount PV is proud to present Solar Roof Talk, a podcast series for rooftop solar installers and others in the solar industry. Hosted by solar industry veterans, Jeff Spies, Senior Director of Policy & Susan Stark, NABCEP Certified PV Technical Sales Professional™ & Product Specialist.

In this episode, Jeff and Sue discuss the GTM Research report: U.S. PV Racking 2017: Landscape, Pricing and Forecasts and a comparison of rail-based vs rail-less pv mounting. Topics include:

  • Comparison of rail-based vs rail-less pv systems
  • Module-level electronic attachments
  • Residential and commercial racking and mounting markets
  • Surprise conclusions from the report

Subscribe to our podcast on SoundCloud or iTunes and follow it here on the blog!

Vlog Series: Installing Wood Blocking

The second video in our vlog series is here! Today’s video is about installing wood blocking. Learn the best tips and tricks from our industry expert and Sr. Director of Policy, Jeff Spies!

As always, we’d love to hear from all of you about your experiences with challenging installations and how you ensured the project was a success. Or if you have a subject you’d like us to cover in this series, comment on the post and we’ll follow up with you. Hope you enjoy it!

Tools & Techniques: Attaching solar on
steep slope roofs

Roofs over 2:12 pitch are considered steep slope and instead of using a waterproofing membrane like a low slope roof, they typically use water shedding roof coverings that rely on gravity to keep the water out of the structure. The significant majority of steep slope roofs use asphalt shingles or tile. The other common steep slope roof options include wood shake, wood shingles, metal shingles, slate, standing seam metal roofs, or exposed fastener metal roofs. There are a variety of roof attachments and flashing methods available for each roof type, and careful selection is needed to insure you are able to deliver a structurally sound, waterproof, code compliant solar attachment system.

Waterproofing basics

Building codes require that roof penetrations be flashed per the roofing manufacturer installation instructions. A significant majority of asphalt shingle manufacturers follow the National Roofing Contractors Association guidelines for penetration flashing which mandate metal flashing for all penetrations and specify the upper edge of the flashing must reach up into the third course of shingles. The vast majority of tile roof manufacturers follow the Tile Roofing Institute’s installation guidelines that requires metal flashing to be installed at the underlayment level and sealed using bibbing or three coursing with roofing cement and reinforcing fabric.

Structural attachment method

Rafter attached systems have been the norm for solar installations as the tried and true attachment method. Building officials allow rafter attachment as long as the roof meets established criteria. An alternate attachment method secures the racking system directly to the roof sheathing. Using sheathing attached systems may be inadvisable since it can be difficult to verify whether the sheathing is reliably secured to the rafters. As a result sheathing attached systems are often not allowed on existing roofs in many jurisdictions. Sheathing attached systems can work well for new or re-roofs applications since the installer and building official can verify that the sheathing is attached to the rafters before the roof covering is installed. If a sheathing attached system is used on a new roof, it’s important that point loading on a single attachment does not get concentrated on a single fastener. This could initiate a structural problem if the fastener pulls out under dynamic uplift forces from windstorms.

This flashed roof attachment is rafter mounted and provides a reliable structural attachment for full code compliance
This flashed roof attachment is rafter mounted and provides a reliable structural attachment for full code compliance

Shingle roof attachment

Options for shingle roof attachments include standoff cone flashings, hooded flashings, and integrated seal flashings. Standoff cone flashing use a metal cone flashing that elevates the seal area above the roof plane. Hooded flashings are inexpensive, but have a major vulnerability as they have an opening on the downhill side of the attachment, which can allow wind driven rain to access the penetration. Integrated seal flashings use rubber seals and can be very effective. Seals located at the waterline will degrade more quickly than elevated seals particularly in cold climates where freezing water can wear out a rubber seal.

Metal cone flashing provides ample elevation of the seal above the waterline, assuring longer seal life

Metal cone flashing provides ample elevation of the seal above the waterline, assuring longer seal life

The patented QBlock waterproofing system elevates the seal of this integrated flashed attachment above the waterline.
The patented QBlock waterproofing system elevates the seal of this integrated flashed attachment 0.7” above the waterline. This approach positions the sealing area in a protective cavity shielding the seal from moisture and UV exposure.

Tile roof attachment

Options for tile roof attachment have expanded dramatically in the past several years and fall into three general categories: standoffs, tile hooks, and threaded bolts. Regardless of which method you choose, flashing at the deck level (underlayment level) is code required by the Tile Roofing Institute. Underlayment flashing can be challenging for certain tile attachments including the sliding track style base mount, but fortunately a growing number of code compliant tile roof attachments include preformed metal flashings to seal the penetrations at the underlayment level. This code compliant tile hook (pictured at top) is quicker to install and has no visible flashing. The standoff on the right is super strong and uses a malleable tile level flashing. Both roof attachments are sold with deck-level flashing that are sealed to the underlayment under the tile.

Tile standoffs

Tile standoffs are much stronger than hanger bolts as they have a larger diameter base and post, but both standoffs and hanger bolts require double flashing since the tile must be penetrated to allow for installation. The tile level flashing can be installed above or below the tile that is penetrated and the secondary flashing at the underlayment level would be sealed to the underlayment using bibbing or three coursing with roofing cement and reinforcing fabric. For curved tile, the TRI requires a malleable metal flashing molded to the tile.

Tile hooks

Tile hooks typically do not penetrate the top of the tile, instead they protrude between 2 rows of tiles. The tile lug will need to be trimmed using a tuck pointing diamond blade to allow for clearance of the hook and insure proper tile seating. Some metal strap style tile hooks allow the weight of the array to rest on top of the tile. This method of attachment is inadvisable, as the array will vibrate on the tile in a windstorm, increasing the likelihood of broken tile. The best tile hooks provide a strong mounting location that elevates the hook and racking system off the tile– preventing contact with the tile under full wind loading conditions.

Tile hook with underlayment bibbing

To be code compliant, tile hooks must have metal flashing installed using Tile Roofing Institute approved underlayment bibbing (shown on the left).Three coursing with roofing cement and reinforcing fabric (shown on right).

Less common roof types

Asphalt shingle roofs and tile roofs represent over 90% of all solar installations in the US, but many solar installers are confronted with less common roofs like wood shake/shingle, slate, or metal shingle. These roof types are often found on more expensive homes and are more challenging for the installer. The benefits of learning how to work on these upscale roof types are fewer competitors and better profit margins. Typically partnering with an experienced qualified roofer is advisable. Metal panel roofs are common in rural areas but exposed fastener roofs (corrugated or trapezoidal) may be less desirable than standing seam roofs as the fasteners often require periodic tightening and access to these fasteners is difficult after a solar installation. Standing seam roof rack systems typically attach to clamps on the standing seams. Standing seam panels are held on with clips, so the installer and building official should verify there are sufficient clips securing the roofing system, so it can withstand the uplift forces from the solar array when subject to strong winds.

This home with Decra metal shingles in Florida uses standoffs with flashing installed with a Decra

This home with Decra metal shingles in Florida uses standoffs with flashing installed with a Decra “Underpan” to channel any leakage safely to the top of the shingles below.

As flashed roof attachment options continue to expand, it’s important to verify your your attachment of choice will provide a reliable, long-term, structurally robust and waterproof system for the life of the roof and array. Your customers will thank you.

…….

This article was originally written for Solar Novus Today

Installing Solar On Metal Shingle Roofs

Over the past few years, our tech support staff has fielded a growing number of questions about metal shingle roofs. Metal shingle installations are more challenging than asphalt shingle roofs or even tile roof projects and require partnering with a qualified roofer. As a result, fewer solar installers bid these projects. However they can be more profitable than other projects as they are less subject to intense competitive pressures. Metal shingles are noticeably more expensive than asphalt shingle and tile roofs. Homes with metal shingle roofs are often in affluent areas with owners that are more likely to invest in solar. These homeowners tend to be less concerned about the modest savings common in grid tie competition and are usually more concerned with an attractive installation that preserves the aesthetic appeal of their pricey metal shingle roof.

To help make sense of this more challenging installation, we contacted the largest metal shingle manufacturers, and developed several methods for installing on metal shingle roofs. While there is a wide array of metal shingles, they typically fall into three basic mounting configurations:

Figure 1: Decra interlocking metal shingles with Quick Mount PV QBase mount installed over Decra underpan

Figure 1: Decra interlocking metal shingles with Quick Mount’s QBase Comp Mount installed over Decra underpan

Interlocking
Interlocking metal shingles most often resemble asphalt shingles or slate. They are directly nailed or screwed to the deck and have interlocking lips on the upper and lower edges, or sometimes on all four sides. These interlocking lips lock together for a lightweight, highly wind resistant roof. This style of metal shingles often requires complete removal of the roof from the ridge to the bottom of the array.

Figure 2: Batten mounted metal shingle

Figure 2: Batten mounted metal shingle


Batten Mount
Batten Mount metal shingles often resemble shake or tile. They typically mount to horizontal wood battens attached directly to the deck with screws inserted into the leading edge of the shingle. Batten mount metal shingles are relatively easy to install solar onto, because the individual shingles can be removed by taking off the screws at the top and bottom of the shingle and installing the mount. 
Figure 3: Counter batten roof

Figure 3: Counter batten roof

Counter Batten Mount
Counter Batten Mount metal shingles are installed onto a grid work of horizontal wood battens secured to vertical wood battens attached to the roof deck. This arrangement is best in a wet climate as it allows for rapid drainage of water that might leak past the metal shingles. An important caution is in order: before quoting any metal shingle project, always check for old shingle or shake roofs under the array. If you find an old shingle or shake roof under the metal shingles, the best strategy is the “strip and go” procedure outlined below. It is very challenging to effectively seal mounts on roofs of this configuration.

There are four methods for installing Quick Mount PV mounts on metal shingle roofs.

Figure 4: The light blue underpan extends under the mount and channels any rainwater harmlessly off the roof just below the mount. Note how the upper edge of the underpan is sealed to the underlayment.

Figure 4: The light blue underpan extends under the mount and channels any rainwater harmlessly off the roof just below the mount. Note how the upper edge of the underpan is sealed to the underlayment.


1) Underpan: Quick Mount PV has worked closely with Decra (the largest manufacturer of metal shingles) to develop a procedure for installing solar arrays on Decra metal shingles (aka stone coated metal panels). Decra is unique in offering a clever drainage pan configuration referred to as underpans. These underpans are positioned under the mount location with a flashing installed over the mount and the shingle installed over the flashing. Any water that hits the mount flows harmlessly down the underpan to the shingles lower down the roof. Since Decra stone coated metal panels are galvanized steel, any contact between the aluminum mount and the metal shingle is protected with a barrier material like a fully adhered underlayment.

Figure 5: The flashing shingle sandwich installation method requires a flashing installed between 2 metal shingles. Note that the lower metal shingle does not need to match color of the upper visible metal shingle.

Figure 5: The flashing shingle sandwich installation method requires a flashing installed between 2 metal shingles. Note that the lower metal shingle does not need to match color of the upper visible metal shingle.


2) Flashing sandwich: For batten mounted metal shingles that do not use underpans (like Gerard), you may be able to use the flashing sandwiching method. This requires purchasing enough of the exact same shingle as is currently on the roof. Color is not important, as these new shingles will be installed under the original shingle with a flashing sandwiched in between. The mount is bolted to the roof deck. Next, cut a 4” diameter hole into the new shingle and install over the QBase Comp Mount. Trim the top edge of the flashing as needed to fully cover the shingle. Finish by installing the original shingle over the top of the flashing. Cut small 1″ wide drainage slots in the butt edge of the top shingle to allow any water that gets onto flashing to easily drain. If the shingles are galvanized steel, use a self adhered underlayment on the top and bottom of the flashing to protect against galvanic corrosion caused by aluminum to galvanized steel contact. Finish by applying sealant around flashing cone to minimize water getting past flashing cone and sprinkle color matching granules into wet sealant to produce an attractive color matched mount. In this configuration, the bottom shingle serves the same function as the underpan in the method above.

 
3) Adhered flashed mount: Metal shingles that are fully interlocked on all four sides require a different approach. There are two possible approaches for “Aluminum Lock Roofing” shingles. The first method involves trimming the top edge of the Classic Comp Mount or E-Mount so the bottom edge of the flashing is just above the butt edge when the top edge is wedged all the way up in the interlock area above the penetration. The flashing is then coated with a sufficient amount of sealant, and the lag bolt is carefully torqued to the proper setting (when the QBlock stops pivoting). When installed properly, the gasket seal is tightly compressed between the flashing above and shingle below providing a reliable long term seal. The second option for interlocking shingles requires cutting a slit in the interlock just above the penetration and slipping the upper edge of the flashing under the second course of shingles until the block is positioned in the proper location. Sealant is applied to the cut area and under the flashing.

Figure 6: This metal shingle roof is installed over an old asphalt shingle roof. The best solar mounting option for this configuration is "strip and go".

Figure 6: This metal shingle roof is installed over an old asphalt shingle roof. The best solar mounting option for this configuration is “strip and go”.


4) Strip and go: If there is an old shingle or shake roof under the metal shingles, the easiest approach would be what is commonly referred to as, “strip and go”. First, a qualified metal shingle roofer would “strip” off the metal shingles from under the field of the array. Then the roofer would “go” by installing a new asphalt shingle roof under the field of the array. This installation method is a compelling option since the customer gets a new roof that lasts the life of the array, and the roofer can warranty the roof and flashed mounts. The long term cost benefits of a new roof under the array are dramatic- saving thousands in repair costs during the life of the solar system. When done properly, “strip and go” has the attractive appearance of Building Integrated PV Systems (BIPV), particularly when installed on batten mounted metal shingles shaped like curved tile or shake. There are six basic steps in the “strip and go” process.

  • Step 1: Roofer removes existing metal shingles under and around field of array.
  • Step 2: Solar installer secures QBase Comp Mounts over new underlayment into rafters using lag screws.
  • Step 3: Roofer installs shingles AND flashings over mounts.
  • Step 4: Solar installer assembles array.
  • Step 5: Roofer installs flashing around perimeter of shingles.
  • Step 6: Roofer installs metal shingles around perimeter of array.

While metal shingles require a bit more research, learning how to install on this high-end roofing system can boost your bottom line and bring solar to homeowners that often struggle to find a willing and able solar installer.

To learn more, register for our next metal shingle webinar on February 12. Or visit our website to download the presentation slides or view a previously recorded webinar.

Fire Classification for Roof-Mounted PV Systems

We recently worked with SolarPro Magazine and PanelClaw to write an article about the new UL 1703 PV system fire classification requirements for roof-mounted PV systems. The article was published in the Nov/Dec 2014 issue of SolarPro Magazine and can also be found on their website.

Until recently, the National Electrical Code was the only widely enforced code in North America with specific require
ments for PV systems. This changed when the 2012 editions of several international codes incorporated PV-specific content. In addition to the new International Fire Code requirements for PV systems—some of which Fortunat Mueller discusses in detail in “Pitched-Roof Array Layout for Fire Code Compliance,” —the International Building Code (IBC) introduced fire classification requirements for roof-mounted PV systems.

The 2013 California Building Code (CBC) and the California Residential Code (CRC) subsequently incorporated the new fire classification requirements. Since no available products met the requirements, the California state fire marshal issued an addendum to Information Bulletin 14-002 on April 29, 2014, advising local code enforcement agencies to temporarily delay enforcement of fire classification requirements for roof-mounted PV systems until January 1, 2015. This delay allowed UL and industry stakeholders time to develop new standards and enabled module and mounting system manufacturers to test products to these new standards.

New Building Code Requirements

The new fire classification requirements for roof-mounted PV systems originate in Section 1509 of the 2012 IBC, “Rooftop Structures.” Subsection 1509.7.2 addresses fire classification: “Rooftop mounted photovoltaic systems shall have the same fire classification as the roof assembly required by Section 1505” [emphasis added].

Fire classification is a fire-resistance rating system for building materials. In some locations, such as California’s wildland urban interface (WUI) areas, building codes require the use of roof assemblies with enhanced fire-resistance ratings. Where this is the case, Subsection 1509.7.2 ensures that installing a roof-mounted PV system does not adversely affect the fire resistance of the roof.

Fire-resistance ratings for roofs. Per IBC Section 1505, roof assemblies are either nonclassified or fire classified. Nonclassified roof assemblies remain untested for fire resistance. Roof fire performance is classified by means of burning brand and spread of flame tests. Burning brand tests simulate what happens when burning embers fall on a roof surface. Spread of flame tests simulate how fire propagates across the roof. Fire-classified roofs are rated—in decreasing order of fire resistance—as Class A, B or C, based on their ability to withstand severe, moderate or light fire exposure.

Since Class A and Class B roofs provide higher fire resistance than nonclassified or Class C roofs, AHJs may require Class A– or Class B–rated roofs in areas with high wildfire vulnerability. For example, the City of Oakland implemented a mandatory Class A fire rating for all new residential roofs after the devastating 1991 firestorm. When California adopted the 2013 CBC and CRC on January 1, 2014, the number of jurisdictions with Class A and Class B roof requirements increased significantly.

Noted code expert Bill Brooks expects this trend to continue: “While current Class A and B fire rating requirements impact only about 20% of California, and only a few percent of the rest of the United States, it is likely that these percentages will rise dramatically over the next few years. The solar industry must be prepared to update its products to meet the demand for higher fire-rated roof systems.”

PV System Fire Classification

A key word in IBC Subsection 1509.7.2 is systems: PV systems—not modules—must carry a fire classification rating. Whereas legacy fire performance tests evaluated PV modules on their own, the new tests evaluate modules in concert with mounting system components. This represents a significant departure in how the industry evaluates PV system component fire performance.

Legacy approach. For nearly two decades, the industry evaluated and classified PV modules according to fire exposure tests outlined in UL 1703, “Flat-Plate PV Modules and Panels.” While the legacy fire performance tests for PV modules borrowed elements from fire exposure tests for roof assemblies, evaluators applied burning brand and spread of flame tests to PV modules in isolation rather than within the built environment. This approach ignores the racking assembly’s impact on the spread of flame. For example, the legacy fire exposure tests do not consider the potential chimney effect where PV modules are flush mounted above a steep-slope roof.

System-level approach. Current building codes require the classification of PV systems using fire-resistance test methods that include both the module and the mounting system assembly. Per CBC Section 1505.9, “Effective January 1, 2015, rooftop mounted photovoltaic systems shall be tested, listed and identified with a fire classification in accordance with UL 1703.” Similar language appears in CRC Section R902.4, except that it replaces “systems” with “panels and modules.” While California is the first state to enforce these requirements, other jurisdictions will eventually follow suit.

Fire Classification for roof-mounted PV systems

Revised Product Safety Standards

Because fire exposure tests now must account for the performance impacts of PV mounting and racking systems, industry stakeholders needed to revise the fire classification requirements in the product safety standards for PV modules and mounting systems. This required new fire-resistance test protocols for PV systems. It also gave rise to a system for categorizing different module types.

UL 1703 and UL 2703 revisions. In December 2010, the UL 1703 Standards Technical Panel (STP) initiated the review process by establishing a fire performance subcommittee. UL published its revised 1703 standard in October 2013 and ANSI formally adopted it as an ANSI standard in May 2014. While the updated UL 1703 has an effective date of October 25, 2016, California has already adopted the new testing and classification approach.

UL 2703, “Rack Mounting Systems and Clamping Devices for Flat-Plate Photovoltaic Modules and Panels,” is nearing ANSI accreditation. This standard references the fire-testing protocol in UL 1703 and further addresses the mechanical strength and suitability of racking and mounting system materials, as well as bonding/grounding assemblies.

Revised fire tests. The UL 1703 STP developed new fire classification test protocols in collaboration with the Solar America Board for Codes and Standards (Solar ABCs) and UL staff. These stakeholders developed interface test methods to evaluate how fire spreads on steep- and low-slope roofs with PV systems in place. Figure 1 illustrates performance of the spread of flame test for steep-slope mounting systems. Figure 2 shows a similar spread of flame test performed for low-slope mounting systems. These new tests evaluate what happens at the shared boundary or interface between the PV system and the roofing assembly.

Nationally Recognized Testing Laboratories (NRTLs) such as CSA, ETL, UL or TÜV perform these new fire classification tests. Per the revised UL 1703 and UL 2703 standards, fire classification applies to PV systems, not to modules by themselves.

Module type testing. There is some continuity between the legacy fire classification tests in UL 1703 and the revised requirements. For example, NRTLs still conduct spread of flame and burning brand tests on the top surface of modules. However, these fire performance test results are now part of a process used to categorize modules according to different types. NRTLs additionally categorize modules according to construction, which includes superstrate material, encapsulant material, substrate material, and frame type and geometry. UL 1703 currently recognizes 15 module types based on different combinations of fire performance and construction characteristics.

Module type testing is a very important part of the revised fire classification methodology. A PV system may undergo up to six tests to receive a fire rating. Classifying modules according to type makes it unnecessary to test each mounting system with every module. Once an NRTL fire classifies a mounting system with a particular module type, you can substitute any other module of the same type—as long as it fits the mounting assembly—and retain the system’s fire-resistance rating.

Installing Fire-Classified Systems

Like any other major change to codes and standards, the new fire classification approach requires some attention to detail. To meet requirements for enhanced fire-resistance ratings, you need to specify a tested, listed and identified fire-classified mounting system. If the mounting system’s fire classification meets or exceeds that of the roof, then the installed PV system will maintain the roof’s fire-resistance rating—provided that you install the mounting system according to the manufacturer’s instructions.

Some installation details—such as the use of deflectors or type-tested modules—can be essential to maintaining a PV system’s fire classification. Other details—such as mounting hardware selection or air gap height—may not matter. When in doubt, consult the product installation manual or an applications engineer.

Deflectors. Some mounting systems use a leading-edge deflector, also referred to as a shield or a skirt, to help slow the spread of flame. Deflectors can reduce the perimeter air gap and thereby mitigate the chimney effect that a roof-mounted PV system produces. To maintain an enhanced fire rating, you must install deflectors if they are part of a listed Class A or Class B assembly.

Type-tested modules. While most mounting system manufacturers perform fire classification tests with type-tested PV modules, some may opt to test their products with specific modules. Where the product listing refers to a specific module make or model, you cannot substitute different modules and maintain the fire-resistance rating.

Steep-slope air gap. Industry studies found that a 5-inch air gap is the worst-case scenario for a spread of flame on a steep-slope roof due to the chimney effect. The default air gap for the steep-slope roof spread of flame test is therefore 5 inches. If you are using a mounting system evaluated with this default 5-inch air gap, then you should be able to install the system at any distance off the roof deck and maintain its fire-resistance rating. However, if this is not the case, you need to install the PV system with the air gap distance used for the fire classification tests, which the manufacturer’s instructions should specify.

Roof mounting hardware. The UL fire test protocols do not specifically address attachments, feet, standoffs and so forth unless the manufacturer requires spacing at a distance of less than 40 inches. On the one hand, if a manufacturer requires specific mounting hardware that was part of the fire classification test, then you need to use the hardware specified. On the other, if a manufacturer does not call out the mounting hardware make or model, then you may use any hardware and maintain the mounting system’s fire-resistance rating.

While system integrators and building officials will encounter a learning curve, the new UL 1703 PV system fire classification requirements should provide a higher level of confidence for building departments, inspectors and PV system owners. You will need to consider which fire-rated mounting systems and module types best meet your needs, particularly when evaluating pricing and inventory issues. Some integrators may choose to standardize on Class A–rated systems that are acceptable in all jurisdictions. Others may opt to purchase Class B– or C–rated systems where a Class A rating is not required, especially if those systems are less expensive.

Written for SolarPro Magazine by:

—Jeff Spies / Quick Mount PV / Walnut Creek, CA
—Mark Gies / PanelClaw / North Andover, MA

10 Tips for Installing Solar Roof Mounts

Our training and tech team spends much of their day answering technical questions on solar mounts for comp shingles, tile, shake, metal shingles and other roof types. We advocate quality installation practices that improve reliability and longevity of rooftop solar systems. Most PV arrays are capable of producing power for 20-30+ years. If the roof and waterproof mounts last the life of the solar system, the homeowner reduces their monthly energy cost and insures clean, emissions free power for years to come.

We’ve compiled our top ten tips for installing solar on shingle and tile roofs. By following these guidelines you will ensure better long-term system quality and lower the cost of power for your customers.

1. Locating rafters
Rafter-finding techniques include attic rafter mapping, rubber mallet roof tapping, drilling two to three holes through the sheathing to locate the edge of the rafter or using sophisticated stud finders like the Bosch D-tect 150.

2. Centering attachment point
Take care to center your lag bolt in the middle-third of the rafter. This ensures the fastener has the structural capacities listed by the American Wood Council charts.

3. Piloting holes
Drilling pilot holes is critically important when using 5/16- or 3/8-in. lag bolts in a 2x rafter. This is true even with the newer generation of self-drilling fasteners (like those from GRK). While these specialty fasteners can be installed in wider lumber without pilot holes, failure to drill pilot holes in the outer chord of 2×4 or 2×6 rafters will likely result in split rafters.

4. Remove shingle nails
Always remove the nails on composite shingles to allow the upper edge of flashing to be 1/2-in. Failure to remove nails is the most frequent mistake when installing flashing. Removing nails allows the flashing to extend up under the third course of shingles for code-compliant, reliable waterproofing.above the butt edge of the third course shingles. Failure to remove nails will prevent the flashing from being positioned up under the butt edge of the third course of shingles and thus become a leak risk, especially when the flashing is positioned under a butt joint between two adjacent sections of shingles.

5. Acceptable working temperature
Shingle temperatures should be between 45° and 85° F to avoid damaging the shingles. When installing on asphalt shingles above 85° F, care must be taken to avoid compression deflection of the flashing from over-torquing the lag bolt. Special roofing shoes or protective mats can be used to minimize the risk of bruising on warm or cold days.

This diagram shows the acceptable position for flashed roof-mounts. Most mounts will require at least one nail be removed.
This diagram shows the acceptable position for flashed roof-mounts. Most mounts will require at least one nail be removed.
6. Flashing width
Asphalt shingle flashings should be at least 9 in. wide to comply with roofing industry best practices. This assures at least 4 in. of coverage from the edge of the hole to the edge of the flashing. More width provides additional protection from wind-driven rain making 12-in. wide flashing very popular. Tile flashings typically are 18 in. or wider to meet Tile Roofing Institute (TRI) guidelines.

This flashed Quick Hook uses a three-course sealing system that is approved by the TRI guidelines. Mastic applied to fiber mesh provides long-term waterproofing of the top and sides of the base flashing to the rolled roof underlayment.

7. Flashing material
Flashings should be made from an NRCA-compliant metal (aluminum, stainless steel, lead or galvanized steel). This flashed Quick Hook uses a three-course sealing system that is approved by the TRI guidelines. Mastic applied to fiber mesh provides long-term waterproofing of the top and sides of the base flashing to the rolled roof underlayment.The TRI requires curved tile flashing be made from malleable metal. SMACNA (Sheet Metal and Air Conditioning Contractors’ National Association) considers galvanized steel to be suitable only for 15 years of service life, and any breach of the zinc coating will cause corrosion and rust staining. For this reason, galvanized is inadvisable in coastal and industrial environments as well as any installation with more than 15 years of expected life.

8. Seal design matters
Select flashed mounts with a robust seal. Seals that are elevated above the waterline will provide longer life than seals at the waterline, especially in freezing climates. Please note that sealant is a helpful addition to a properly installed flashing; however, when used alone, sealant is not an alternative to metal flashing required by building codes.

The Tile Roofing Institute guidelines require a base flashing be used at the underlayment level. The TRI guidelines are code-required for most tile roofs. Underlayment bibbing is one of two accepted methods for waterproofing the base flashing.

9. Install base flashing on all tile roof mounts
This frequently disregarded code requirement will cause premature leaks on tile roof installations within five to 10 years. The Tile Roofing Institute guidelines require a base flashing be used at the underlayment level. The TRI guidelines are code-required for most tile roofs. Underlayment bibbing is one of two accepted methods for waterproofing the base flashing.All major tile manufacturers abide by TRI’s guidelines which mandate flashing at both tile and underlayment levels. All tile standoffs need a “base flashing” that is bibbed or three-coursed to the underlayment. Then the “tile-level flashing” is installed either on top or just below the tile. Tile hooks also require base flashing, but tile-level flashing is not required since the tile is not penetrated.

10. The benefits of re-roofing under the array before solar installation
Most arrays are installed on roofs with less than 10 years of remaining life. It is strongly advised that the installer replace the shingles or tile underlayment under the field of the array before installing solar. Replacing the roof under an average-sized array prior to PV installation will add $1,000 to $1,500 to the initial installation cost. Homeowners who ignore this advice will pay an additional $3,000 to $5,000 to remove and reinstall an average-sized system for the inevitable roof replacement. Simply stated, unless your roof is relatively new, re-roofing prior to PV installation is the most effective strategy to getting the best financial performance from a solar investment.

Written by Jeff Spies. Original article appeared in Solar Builder’s May/June issue.