Solar Roofing — Flat and Metal Roofs with Integrated Solar Panels

Solar Roofing - Flat and Metal Roofs with Integrated Solar Panels

In this article we will discuss solar roofing systems, which integrate roofing materials with solar PV panels or solar thermal systems. Specifically we will cover, metal roofs, PVC flat roofing membranes and asphalt shingles. Although most roof-mounted solar systems are installed on top of an existing roof be it an asphalt shingles roof or any type of flat roof these solar systems are not integrated into the roofing material, and therefore are not solar roofs.

Why Are Solar Panels Installed On Roofs?

Most solar systems are installed on a roof of a house or a building. The exception are solar farms or ground-mounted solar installations, but these are rare, and are usually 100% commercial solar systems. There are a number of reasons why most solar systems are installed on roofs. The primary one being limited space especially in an urban setting, where roofs represent significant unused space. Another reason is that usually roofs are not shaded by trees, nearby buildings, etc they are the highest point of a building with great sun exposure, which makes them perfect to install solar panels on.

What Is a Roof-integrated Solar Systems?

Solar roofing is a final product, which integrates solar panels with the roofing material suitable for either a sloped or a flat roof. The solar panels used in solar roofing are usually thin-film photovoltaic laminates. Most popular Solar PV laminates commercially used today, are the Unisolar thin-film PV panels.

Solar Metal Roofing

Solar Metal Shingles

Solar Flat Roofing

The main reason why flat roofing materials manufacturers began developing solar flat roofing systems was to A) eliminate roof leaks associated with flat-roof solar installations, and B) sell more flat roofing materials. which is their main business after all.

Solar Flat Roofing is a great concept, but has some limitations. First, the angle on the solar panels is flat, so these panels will not catch as much sunlight as tilted or sloped solar panels. Second, solar flat roofs will be much more effective in warm climates vs. colder northern climates such as New England, as in the winter, flat roofs are completely covered with snow and sunlight does not get through to the solar panels.

That said, the benefits of solar flat roofs far outweigh their drawbacks in colder climates. The solar PV panels that are integrated into the roofing membrane eliminate 99% of roof penetrations, considerably reduce the weight of the solar system and the total solar system price. Not only are the solar panels prices lower for roof-integrated solar systems, you also eliminate the entire rack-mounting system (which costs about $1 per watt of your solar system) and that is not small beans you will save about 10-15% off your total solar system cost. Also, since the roof solar system weighs much less than regular solar panels mounted on racks, you also eliminate substantial weight, and your building construction costs will be much less, because you can reduce roof load requirements.

Solar Asphalt Shingles

Solar asphalt shingles are very similar to solar metal shingles described above. The main difference is that they are designed to work with 3-tab or architectural asphalt shingles instead of metal roofing shingles.

Although solar shingles may seem like a great concept, please consider the following factor, which makes them not such a viable option when it comes to solar roofing. Solar shingles, just like metal solar shingles, take a very long time to install, as each shingle must be connected to the rest of the solar system in the series. However, unlike solar metal roofing shingles, there is no room to conceal the terminals under the shingle, so all connections must take place inside the attic space. Holes must be pre-drilled for each shingle, and terminals are fed inside the attic where they are connected.

This slows down the installation process significantly, and usually you cannot finish this in one day. If it starts to rain, your roof is toast. There are too many penetrations under the solar shingles, and it is very easy for water to get in. Of course, there are ways to prevent the roof from leaking even if it rains and the roof is not finished. You can run the last row of shingles and overlap it with roof underlayment, which will prevent the roof leak. Still, this makes the total job that much more complicated and costly.

One more thing to consider is the fact that asphalt shingles only last about 15 years and will have to be replaced down the road, where as a metal roof will last pretty much forever, or at least the lifetime of your house.

Solar Roofing Resources

Solar System Guide everything you need top know when designing a residential Solar PV system positioning of your roof toward the sun, shading and angles of your solar panels, choosing the solar panels and inverter, etc.

Metal Roofing Materials learn about different metal roof types and which metal is better to use steel, aluminum, copper, zinc, etc. as well as learn more about metal roofing prices.

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