Replies

1. GBA Editor
   Martin Holladay|Jul 13, 2015 07:09am|#1

   Joseph,
   Q. "I have an unvented cathedral ceiling roof containing both closed-cell and open-cell polyurethane insulation, approximately R-60. Does this present any special problems for the installation of the two different types of roof-mounted solar cells or shingles?"

   A. No.

   Q. "Please compare residential roof-mounted solar panels to roof solar shingles -- Advantages / disadvantages -- Relative costs."

   A. PV shingles make up only a tiny part of the market. Many manufacturers who tried to enter the market have already withdrawn their products and stopped production. In all cases, PV shingles will cost more than PV modules installed on racks above the roofing.

   My guess is that you won't find many contractors who are interested in installing PV shingles. But if you can find such a contractor, you can get your own cost estimates.

2. 
   Daniel Young|Jul 13, 2015 08:25am|#2

   I concur with Martin. We get a few inquires about solar shingles each year. We look into the new products as we find them/ are made aware of them. So far in each case we find the cost will likely be DOUBLE a standard roof mounted system. And not look as good as the client expects due to the new code requirements.

   The added cost comes from 2 main items.
   1. The solar shingles themselves often cost 50% more than the commodity framed solar modules.
   2. A lot of solar installers do not want to become roofers (in that, they start to take on a leak warranty of an entire roof, rather than just the handful of flashing we install on a given job). So a roofer is usually asked to install the actual shingles so it is all under the roofers warranty. That usually adds even more cost. (either roofers hear the word "solar" and see dollar signs, or they are adding a big safety factor to their numbers since this is likely the first time they are going to deal with the product, they don't want to be solar installer any more than solar installers want to become full on roofers)

   Also, most solar shingle products are about half as efficient as the standard framed crystalline modules, so it becomes much less likely that you can install enough solar on the roof to offset a majority of a standard homes utility bill.

   We also noted that right now there is no "good" way to make these solar shingle systems compliant with the 2014 NEC (National Electrical Code), which requires the ability to bring all voltages in the system down below 30V within seconds of shutting the system down. It can be done with a disconnect switch mounted next to the array, some inverter manufacturers also are coming out with smaller boxes that do the same thing, but that really works against the aesthetic that most people are going for with a solar shingle system.

   The market essentially chose it's champion for the time being, framed poly crystalline or mono crystalline solar modules. Shingles have tried a few times to break in to the market, along with other BIPV (building integrated photovoltaics) types, but none have really ever taken hold.

   But they look really slick when installed (minus the new code-required disconnect), you simply have to be prepared to pay for it in the end. Take the idea of doing this for economic reasons and throw it out the window.