Solar roofing is an alternative roofing option that can not only lower your mains energy consumption but also provide sustainable exterior protection from the elements. It comes as no surprise, therefore, that it has crept into mainstream territory in the U.S. over the past decade. And it’s only bound to get bigger.

But while the average Joe has a good general awareness of its many advantages, few have so much as a passing knowledge of the way solar roofing works, how it was developed, and the different components that make up a solar roof. That’s what we’re here to discuss.

Solar roofing is a type of roofing that makes use of photovoltaic cells (also known as PV cells or solar cells), small electrical devices that generate electricity when exposed to light.

While PV cells weren’t discovered until the 1800s, solar power itself dates as far back as the 7th century B.C. Written and archaeological evidence of the Greeks, Romans, and the early Chinese using objects like mirrors, magnifying lenses, and even bronze shields to light fires have been found.

Part 1: What is Solar Roofing

Part 1: What is Solar Roofing

Solar technology remained rudimentary, however, until 1767, when Swiss physicist Horace-Bénédict de Saussure built the first successful solar oven. Robert Stirling, a Scottish clergyman, stepped it up a bit when he patented the first regenerative heat exchanger (which he called the ‘Heat Economiser’) in 1816. Stirling’s heat engine paved the way for the dish/Stirling system, which uses concentrated thermal energy from the sun to produce power. Next came French physicist Edmond Becquerel, who discovered the photovoltaic effect and built the world’s first PV cell in 1839.

SOLAR POWER PIONEERS

Part 1: What is Solar Roofing

While these were the first tentative steps towards practical solar power, several other significant scientific milestones have been made since, leading up to today’s solar panels and shingles.

Modern solar panels are made up of layers of silicon semiconductors hooked up in series or parallel to non-magnetic conductors. Although it’s true that stronger sunshine produces more electricity, solar panels do not require direct sunlight to generate power, which is measured in kilowatts peak (kWp).

Solar shingles, on the other hand, are thin film solar cells similar in size, flexibility, and general aesthetics to conventional asphalt shingles. They have a dark purplish-blue color and usually measure 12 x 86 inches, with 5 x 86 inches of exposed surface once installed.

Solar panels generally have a much higher conversion efficiency than solar shingles: 20.3% versus the latter’s 10%. But breakthroughs in copper indium gallium diselenide (CIGS) technology have made it possible for solar shingles to reach a comparable conversion efficiency of 19.9%.

Part 2: why solar roofing

Although the use of solar roofing is not yet as widespread here as it is in Europe, Scientific American reports that PV installations in the U.S. have still increased six-fold from 2010. Roughly 200,000 U.S. homes have solar to date, with total energy generation at 12,000 megawatts.

A lot of factors have contributed to this surge in numbers, one of the biggest being the continuous and active promotion of solar power by federal and state governments, alternative energy providers, contractors, and nonprofits. And they have very good reasons to push for solar:

Reason #1: Economy

While the upfront cost of a solar roof is still high in the context of roofing, the cost of installation has fallen by at least 60% since 2010. The average cost of solar panels is now at $0.613/watt, while average PV system prices are at an all-time low of $2.89/watt.

As for how much it will cost to put solar panels or shingles on your roof, the exact figure will depend on where you live in the US. Here are the numbers for Maryland:

Source: http://pureenergies.com/us/blog/infographic-how-much-does-solar-cost/

Part 2: why solar roofing

And that’s not even counting the cost offset by your mains energy savings, the 30% federal renewable energy tax credit, state property tax exemptions, local rebates, and the amount you can get selling your unused energy back to the grid.

Reason #2: Reduced carbon footprint

Because solar power is green, renewable energy, a typical residential PV setup can help save over 30 tons of carbon dioxide emissions over its lifetime. And on a global scale, solar power saves 75 million barrels of oil and cuts our carbon dioxide emissions by 35 million tons each year.

Reason #3: Increased property value

Solar roofs add an average of $5.50/watt to the resale value of your home: an average added sale premium of $16,500 for a 3-kW system, $33,000 for a 6-kW system, and $49,500 for a 9-kW system. Homes with solar also sell faster.

Reason #4: Job opportunities

Solar roof installation across the U.S. also opens up millions of opportunities for employment. Helix Recruiting says that assuming 100% market penetration by 2030, solar roofing has the potential to create 480,000 jobs for installation plus 240,000 jobs per year for maintenance. The total is a whopping 4.8 million jobs for the next 20 years.

While these aren’t the only benefits of switching to solar roofing, these are the areas where its impact is felt the most.

Part 3: How Is Solar Roofing Installed?

While the basic components of a solar roofing system are the same regardless of application, the installation process and the steps leading up to it depend greatly on the type of roofing system you have.

You’ll notice that the considerations outlined below are for solar panel installation. Because they cannot be positioned, solar shingles have even more stringent installation requirements.

Part 3: How Is It Installed

LOW-SLOPE ROOFS

Low-slope roofs, which have pitches equal to or less than 3:12, are excellent platforms for solar power systems. The primary concern when installing PV systems on these types of roofs is weatherproofing.

FLASHING. Because PV installations involve new roof penetrations, flashing will play a crucial role. Flashing details and procedures vary according to the type of roof: an asphalt roof uses a different flashing membrane from a single-ply EPDM roof, etc.

WIND RESISTANCE. Wind resistance is a huge consideration if a rack-mounted solar system is to be installed in the corner zones or at the perimeter of a low-slope roof, where wind loads are highest. Ballast can be used, although that solution isn’t as reliable against uplift as structurally attached equipment.

OTHER CONSIDERATIONS: fire resistance, roof warranties and service life, mounting options, drainage and dirt buildup, rooftop foot traffic

STEEP-SLOPE ROOFS

Steep-slope roofs present a bigger challenge to PV system designers and installation contractors. To ensure a code-compliant installation, these factors must be considered:

USABLE SPACE. How much shade your roof gets has a big effect on the amount of energy your solar roof will be able to generate. Placement will also depend on obstructions like skylights and roof vents. Also, some jurisdictions and fire departments require a setback from your roof eaves and ridge.

ARRAY LAYOUT. Planning a layout is tricky because not only should it allow for maximum ease of assembly and efficiency in the use of materials, but it also needs to consider the demands of the client, architect, PV system designer, and sales team.

OTHER CONSIDERATIONS: wind, snow, and earthquake loads, the array’s dead load, aesthetics, thermal effects, roof material

Because planning and installing a solar roof safely and to code is such a rigorous process, it is a job best left to the professionals. Remember that solar panels and shingles are promising technologies, but the only way to maximize them is to put them in the hands of a licensed, trained, and insured contractor.

Part 3: How Is It Installed