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5 Popular Roofing Materials and Their Compatibility with Solar Panels

One of the intricacies of solar installation that oft goes unmentioned is the penetration of roofing material in order to reach the roof framing underneath. While the process of attaching solar panels to the structure itself is fairly universal—panels are mounted on racks which are fastened to the rafters—there are many different types of roofing.

Regardless of the type of roofing material, it must be penetrated in order to secure the panels. Given the obvious differences between, say, sheet metal and clay tiles, it logically follows that ease and method of installation will vary to some degree; and in fact it does. Following are five popular roofing materials and a brief investigation into their compatibility with solar panel installation.

Asphalt (Composite) Roofing

Somewhere near 90% of all homes in the United States have asphalt roofs, and that is just fine for solar installers. Asphalt shingles are the easiest to work with and the cheapest to replace. They can be walked on without much hesitation (outside of personal safety) and are easy to cut, remove and re-install. Typically, the solar installers will remove what shingles are necessary—and this goes for any type of roofing—install their mounting hardware, and then have a roofer come in to replace or patch where necessary before the crew actually installs the panels.

Sheet Metal

Metal roofs can be tough to walk on, and the steeper the roof pitch, the more treacherous it gets. So you can expect a little extra in labor costs from extra time taken to ensure safety. Other than that sheet metal shouldn’t be too difficult to work with. Once the rafters are located (which itself can take time, again regardless of roofing material) the metal can be drilled through and fastening hardware installed. A sealant—probably of the silicone variety—would then be used to ensure waterproofing. A hole or holes would also be drilled for wiring to enter the roof’s interior.

Wood Shingles

Wood shingles can also be quite difficult. They are hardy roofs but expensive and not always easy to patch or replace. Replacing shake shingles takes considerably more time than composite shingles, so expect added costs for material and labor to do it. They can also be dry from baking in the sun, so solar installers will need to be light footed and still some may crack, split, or even slide out. Shake roofs require some maintenance as leaves and debris more easily collect on them and moss will even grow in bunches if the roof is not kept clean. The point is to make sure a shake roof is in good condition before installing panels over it.

Spanish Tiles

Spanish tiles (ceramic or clay tiles) are perhaps the most difficult to work with. They are expensive to install or repair and are very fragile. Inevitably the solar installers, no matter how careful they are, will break some tiles. Also the tiles will need to be drilled through in order to fasten the panels, which takes time, and the rafters can be harder to find because the tiles are inflexible. It is arguably this incompatibility with solar panels that makes solar roof tiles the most popular and innovative segment of building-integrated photovoltaics—it’s easier to just remove the clay tiles and replace them with tiles that produce electricity.

Slate Tiles

Slate is the classic choice. In fact you might still be able to find some classic slate roofs as much as a century old and still in top condition. Slate, when properly installed, is perhaps the most durable roofing material in existence. But when it comes to installing solar panels, slate reacts in much the same way as Spanish tiles—not kindly.

Slate tiles are fragile underfoot and even the most careful installer can’t be blamed for some broken tiles. Furthermore, finding replacement tiles that match the existing roof can be quite difficult because slate products, as a natural stone, will vary by lot. Slate is also very expensive to install, so added costs will pile up for slate, and likely more than any other roofing material.

On the bright side, because slate is so durable, once the panels are up and roof repaired you won’t have to worry about removing the panels to replace the roof a few years down the road. In terms of hiring a solar contractor, try to find someone who has experience with slate roofs, and make sure that if the contractor subcontracts the roofing repairs that the roofing contractor has detailed experience with slate roofing. Slate tiles are not so easy to install and while they can last seemingly forever, if not installed properly, they could be useless from day one.

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