Does My Home Have a Good Roof for Solar Panels?

With solar panels dropping in cost and increasing efficiency, now is the time for homeowners to invest in renewable energy. On or off-grid solar photovoltaic systems can power your home reliably and sustainably for the next two to three decades. Even if you don’t have the savings to install a full solar system right now, you can at least make sure your home is “solar ready.” But homeowners have questions: what are the basic system requirements? And since most panels are installed on the roof, what type of roof works best with solar panels?

Basic Roofing Requirements

First, your home needs to be correctly oriented to take advantage of free energy from the sun. In the northern hemisphere, this means having a roof that faces south or southwest. Roofs that face north or pure east will often not receive enough direct sunlight to make solar panel installation efficient and cost-effective. Correct home orientation is also a basic tenet of passive solar design and can significantly increase the energy efficiency and thermal performance of your home.

Second, make sure that your roof does not suffer from large amounts of shade cast by neighboring homes, buildings, trees, chimneys, or other types of vegetation. If you do not have micro-inverters, consistent shading on even one of the panels can block the energy output of the entire string of panels. (If there is no way to avoid regular shading on your roof, you will want to invest in micro-inverters and bypass diodes. This minimizes the effects of partial shading by allowing the solar electricity produced in the panels to flow around the shaded panels or solar cells.)

Third, you will also want to consider the pitch of your roof. Roofs with pitches anywhere between 30 and 45 degrees will generally work well. Roofs with extremely steep pitches, such as A-Frame homes, might make solar panel installation more difficult while also compromising the efficiency of the panels. Ideally, solar panels work best when fixed to a roof angled at a degree equal to the latitude of its location. For example, solar panels installed in a home in Chicago would do best with a roof angled at around 41 degrees.

Solar Panels and Different Roofing Materials 

The good news is that you can install solar panels on virtually any type of roofing material. That doesn’t mean, however, that all roofs are built alike for solar panels. Different roofing materials can lead to both positive and negative consequences that can affect the performance, cost-effectiveness, and durability of solar PV panels. Below, we look at a few of the pros and cons of installing solar panels on some of the most common types of roofing materials.

Asphalt Shingle Roofs

Asphalt shingles are by far the most widely used roofing material in the United States. On the plus side, solar panel installation on top of asphalt shingle roofs is straightforward and only requires drilling studs to into roofing 2x4s where panel mounts are placed. Metal flashing is placed around these holes to avoid potential water damage. This type of roof allows for easy and relatively inexpensive installation. One of the main drawbacks is that asphalt shingle roofs only have an expected lifespan of around 15 to 18 years, while solar panel warranties typically last up to 30 years. Homeowners will likely have to replace their roof sometime during the lifetime of their solar panels. This process of taking down and reinstalling the solar panels may lead to extra expense and possible damage to the solar array. For wood shingle roofs, solar panels are also relatively easy to install; though wood shingles can be brittle and prone to cracking during installation.

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Clay Tile Roofs

Clay tile roofs are a beautiful and natural roofing option. Unfortunately, the installation of solar panels on this type of roof is generally labor-intensive and can lead to higher installation costs. Most installers will be forced to remove parts of the clay tiles to access the studs where the solar panel mounts are fastened. In the best-case scenario, the clay tiles can then be replaced around the solar mounting rack. The downside is that installers will have to purchase and install custom-sized hooks and flashings to cover up the holes where the mounting racks are bolted into the roofing studs. This can increase cost and compromise the aesthetics of a clay tile roof. Improper installation can lead to damaging water leaks. The same concerns relate to both slate and concrete tile roofs.

Flat Roofs 

Multifamily buildings often have flat roofs of concrete or EPDM (rubber membrane) that are an excellent option for solar panel installation. While you will have to invest in a metal racking system to prop up your panels, installers can create this racking at an optimum angle for maximum efficiency. Installers can use a ballast system to install these types of solar panels. A ballast system makes the penetration of your roof unnecessary and will not compromise your building envelope.

Metal Roofs

Metal roofs are perhaps the best fit for solar panel installation. Metal roofs offer a solid surface and long-term durability for the panels. For homes that have a standing seam metal roof, many installers will not even have to drill holes in the roofing. The panel mounts can be clamped and firmly secured to the raised seams. If installers do need to drill holes through the roofing material, several waterproofing sealants are compatible with metal roofs to prevent moisture from getting into your house. Metal roofs can easily last for anywhere between 40 and 70 years. And, because they often contain large amounts of recycled aluminum, metal roofs one of the most sustainable roofing alternatives.

Solar Roof Shingles

Solar roof shingles are small solar panels embedded in each roof tile, combining the function of a roof and solar panel into one product. Typically, these are the most aesthetically pleasing solar roof types due to the design integration of the solar panels. Several options are becoming available. Tesla entered this market with much fanfare. The 3 in 1 Roof is another innovative product that combines solar roof tiles with added insulation and wind protection. These mini solar tiles act as a platform ideally suited for building-integrated photovoltaic (BIPV) rooftops. The 3 in 1 roof tiles are composed of heat-resistant closed-cell foam and coated with a durable geopolymer. The roof tiles are therefore better insulated, allowing them to operate at optimum temperatures for maximum efficiency.

Additional Considerations

For any roofing system with added solar panels, you might want to be able to access to your roof—to shovel off snow or clean your panels. If you live in a snowy climate, consider adding snow guards.

Bottom Line

If you are building new or replacing your roof, your choice of roofing materials plays a significant role on your home’s insulation, beauty, long-term durability—and your wallet. So if you want to produce your own renewable energy, it’s worth knowing more about the options best suited for solar panels. And if your budget allows, go with a metal roof!

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.