Inspecting Solar Roofing Shingles

by Nick Gromicko, CMI®, Roberta Farsetta and Kate Tarasenko

Most homeowners want their homes to look aesthetically pleasing. This affects both seller and buyer because, after all, curb appeal is important for resale value. With this reality comes an ongoing challenge for the home inspector:  Was an improvement made to add curb appeal, or for another reason? Is the quality of installation and concept behind the improvement worth it?  Some of these answers are irrelevant to the home inspector and his duty to inspect and report. But others may have an impact on what the inspector should inspect and report. One of these improvements is solar roofing shingles, including their characteristics, cost factors, longevity, inspectability, and related components in the photovoltaic configuration.

Solar Power Choices

Both solar roof shingles and solar panels have positive and negative aspects. It’s likely that, for the homeowner, deciding whether solar shingles are better than traditional solar panels will come down to whether they will be installing them on a new roof, and how concerned they are about aesthetics. Cost is always a factor, too. In most cases, traditional solar panels are the most suitable option, as they are widely available and a proven energy solution that often integrate well with the dwelling's configuration. 

Solar roof shingles or solar roofing tiles are actually small solar panels made to look like asphalt shingles. They are small and rectangular and made of glass, making them both strong and flexible. Solar roof shingles incorporate the newer thin-film solar technology into their design. They have a low-profile appearance. Their electrical output boasts efficiency, and this will continue to improve over time. Although efficient, they do lag slightly behind the output of traditional solar panels, for now.  And, like any component of a power array, they are strung together.

Solar shingles are photovoltaic cells designed to look like and integrate with conventional asphalt roof shingles. First commercially available in 2005, solar shingles were much more costly than traditional bolt-on photovoltaic panels, and thus were used mainly by those wanting to go solar but maintain a traditional roofline. Recently, solar shingles have become more price-competitive with traditional solar panels, and have gained somewhat in popularity.  Eco-conscious homeowners might find solar shingles an especially attractive option when they are re-shingling anyway, since the solar shingles also double as functional, protective and weatherproof roof shingles in their own right. A solar shingle can, in effect, replace a roof tile. It fits flush among other solar shingles, or it can be used in combination with traditional roof tiles. This improves the aesthetics over that of a conventional rooftop solar panel installation. Solar panels are typically installed over a sound roof, using metallic tracks, standouts, shims and brackets to raise the panel a couple of inches above the roof surface. Compared to the new solar roofing shingles, the older installations are unsightly. Surveys show that homeowners prefer the sleek look of the newer shingles over that of a traditional solar panel installation.

Installation Costs

When taking installation costs into consideration, although solar shingles seem pricey compared to traditional solar panels, a closer examination reveals that the price may be roughly similar, or even a bit less. The final price also depends on the type of system installed and its usage: weekend visits or year-round; off-grid, grid-tie, or other; the size of the home and the size of the roof; average KW usage; the orientation of the roof; etc.  

Taking an average-size home, if the existing roof is in generally good condition, without major defects, and has 30 years of remaining service life, the price for a complete solar panel system at year-round usage of about 11Kw may cost an average of $25,000. If a new roof is required, the cost may increase by $10,000, installed, tested and commissioned. A solar panel roof of the same power capacity may cost around $31,000. Those prices will vary by geographic region and availability. As prices come down further, solar roof installations will become a more common sight. Considering that some systems have a warranty of 25 years, homeowners are also using concepts such as true return on investment as justification. No longer is the roof thought of in terms of how many years it will protect the dwelling. Now it is also viewed as how soon the capital outlay can be offset in energy savings over the course of five-, 10- and 15-year periods, with 10 years remaining, with a positive economic impact on the operating costs of the residence.

Efficiency Improvement 

When solar roof shingles first came to market, the thin-film technology they used wasn’t nearly as efficient as the traditional silicone solar cell. The higher-quality solar shingle initially provided only around 10% conversion efficiency, whereas a high-quality solar panel provided around 16%. Conversion efficiency varies. SunTegra, CertainTeed, Tesla, and others are all improving. Traditional solar panels boast around 20% conversion efficiency. The latest generation of solar shingles' performance is quite promising in improving that percentage.

Another factor concerning the efficiency of solar roof shingles versus solar panels comes down to the positioning of the solar cells. With solar shingles, the angle and tilt of the solar cells is limited to the angle of the roof and, therefore, limits the optimum conversion efficiency of the array. However, the positioning of traditional solar panels, isn’t limited to the angle of the roof. Instead, the tracking that rooftop solar panels sit on can be adjusted to provide optimum conversion efficiency. Traditional solar panels can also be installed with an automated tracking system that follows the sun during its daily cycle across the sky. Of course, with solar panel installations, the heat generated by the panels and their weight are also considerations which affect existing roof conditions and roof structural loading. Again, not so with solar shingles.

Installation Principles

Each manufacturer has its own set of installation instructions. As an example, CertainTeed utilizes the concept of installing the solar shingles in harmony with conventional asphalt roofing shingles. Similar to blocks, the solar shingles are assembled and installed in sized configurations, combining individual shingles into lines and rows equaling whatever area is to be covered. Then, the perimeter of the area is surrounded with manufacturer-supplied flashings, which are screwed into the roof's sub-surface, much like skylight flashings. Conventional asphalt shingles cover these flashings. Each shingle is connected, but wiring sits below the shingle, and above the roofs sheathing. This eliminates individual roof penetrations per shingle. A single entry point for wiring enters the roof and must be enclosed in metallic conduit, per NFPA/NEC® requirements. The DC output from the solar shingles then goes to batteries or an inverter for conversion to alternating current. CertainTeed’s solar shingles are individually rated for 250 pounds per square foot, but the manufacturer still does not recommend walking on the shingles to prevent damage to the solar cells. In addition, solar roofing shingles are extremely slippery. These systems are typically installed after an electrical permit is issued. The systems are inspected, tested and commissioned for proper installation, safety, functionality and performance.

Any damage to shingles should be evaluated in terms of electrical performance, protection of the dwelling (as with any roof), water intrusion, and electrical safety. If a solar shingle needs to be replaced, that shingle (and possibly others around it) will need to be removed, temporarily exposing that section of roof to the elements. The process of replacing a traditional solar panel is much easier. Simply removing a solar panel from a racking system can be done much faster than replacing an individual shingle in the middle of many shingles, which are flashed in place. Finding a defective roof shingle, whether due to electrical efficiency or wind/rain/element protection, could be a major challenge. 

Inspecting for Condition and Functionality

Unless the inspector is also an electrical engineer or bonafide expert in photovoltaic systems (with a thorough understanding of both installation and electrical line diagrams), diagnosing the overall health of one of these systems is beyond the scope of a standard residential inspection. Choosing to exceed the standards of practice the inspector follows is a matter of individual choice.

Actually walking on the solar shingles is not recommended because they are slick and they can easily break. So, it helps to have a working strategy as to how to handle the inspection of solar roof shingles or tiles. The inspector should stick to the obvious: the condition of the individual shingles, including cracks, dents, hail damage, warping, blemishes, etc. Then, examine the flashings. Check the condition of adjacent roofing materials and their flashings. Look in the attic for signs of moisture or water intrusion. Look at the electrical feeds from the solar array to make sure they are in conduits, etc. Examine the system first as a roof, and then as an electrical-generation system.  And be sure to take precautions to protect yourself using safety guidelines and common sense.

Although not required, including additional information in your report may be useful for your client, such as the components’ manufacturer(s), any revisions of shingles, the age of the components, including the batteries, etc. Observe how the system is interconnected. Where are the roof penetrations? Where is the conduit routed? Is it secured? Where is the inverter? What type of battery system, if any, is utilized? When was the system installed and last tested? This kind of information can be useful to your client.

And, above all, be sure to include a disclaimer in your pre-inspection agreement that states that you are not an expert at photovoltaic systems and cannot warrant the functionality or longevity of the solar roofing system. State that doing so is beyond the scope of your standard home inspection. Offer no written or oral opinion beyond what you state in your inspection report as to the visible condition of the accessible and observed components.

Due to the scope of a standard home inspection, as outlined in InterNACHI's Residential Standards of Practice, the inspector should limit his/her opinion of the solar roofing components to that of the roof’s intended function related to protecting the structure. It's important to manage the client's expectations by being specific as to what is and is not included in the inspection. If the roof's solar power system is not functioning as intended, either due to damage, improper installation, manufacturer defects, or inefficiency, the inspector should report this and defer further evaluation by a solar power systems expert.

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Author Roberta Farsetta has been involved in the inspection industry for nearly 20 years. An inventor and entrepreneur, she has performed inspections in New York State, and is an indoor air quality expert. She is also a trained and experienced architectural draftsperson. A freelance author and researcher, Roberta is married to Certified Master Inspector® Joe Farsetta, a nationally recognized educator, and Chair of InterNACHI’s Ethics and Standards of Practice Committee.