Solar Roof Shingles: Essential information before you buy.
Solar roof shingles (also called solar roof tiles and photovoltaic [PV] shingles) provide a new way to incorporate solar energy into your home. Solar shingles are a cost effective alternative to the large, unsightly panels that have traditionally been used to collect solar energy.
Solar shingles are installed on your home's roof and provide not only a durable roof but also electricity. In addition to shingles, there is also a PV laminate available for metal roof applications.
One of the many benefits of solar roof shingles is their appearance. These shingles look like traditional roofing and they replace the need for unsightly, bulky solar collectors.
The performance of solar cells is measured in terms of their ability to convert the sun's energy into electricity. The primary material used for this is silicon (specifically, "amorphous silicon"). This silicon is incorporated into what is commonly referred to as "thin film solar cells."
These cells use layers of semiconductor materials only a few micrometers thick. This is what has allowed the development of solar roof shingles. The shingles are connected to a stainless steel substrate. They are coated for weather resistance and usually carry a 20-year warranty.
The shingles look like conventional asphalt or fiberglass shingles and are installed with roofing nails over standard roofing felt.
Some Challenges of Solar Roof Shingles
Planning a solar roofing project takes careful consideration. Due to their specific needs, solar shingles are best utilized on new construction versus an existing home. We recommend working with your designer or architect early on to ensure a code-compliant, smooth installation.
Two things to consider include spacing of framing members and allowing for adequate working space in the attic.
Installing solar shingles is very similar to installing conventional shingles. They shingles are installed in horizontal courses with a standard 9-inch offset from row to row. This creates two vertical columns of wires that are 3-1/2 inches apart. These wires are then routed through two parallel raceways.
In a typical application, 30 to 40 solar shingles will be wired in series. This usually requires 100 to 120 sq ft of roof space. The efficiency of these shingles is about half that of a crystalline array (i.e., traditional solar panels), so it will require twice the space.
The pitch of the roof needs to be a minimum of 3:12. A typical installation would include 5-6 courses of conventional shingles at the eave and peak in order to meet the National Electric Code. Other considerations include planning out your placement of the shingles to avoid needing to cut them (they cannot be cut) and making sure you have access to the wiring in the attic (don't install on overhang or eaves).
There are several raceways available in which to run your wires. A good raceway should have various snap-together corners, cover pieces, and junction boxes.
In summary, there are some disadvantages to using solar shingles. Installation requires careful planning and additional labor from installers. They are less efficient than traditional crystalline PV modules ("solar panels") so they require more roof space.
These disadvantages are small when you consider that solar shingles provide an aesthetically pleasing way to harvest solar energy in any urban or suburban neighborhood.