Rob Haddock CEO and Founder, S-5!
Canada’s renewable energy industry is poised for growth thanks to the introduction of numerous federal, provincial, and municipal energy programs and incentives aimed at promoting the integration of solar and reducing consumers’ energy bills.
On a federal level, the federal tax provision for clean energy enables businesses to depreciate the costs of their solar power systems at an accelerated capital cost allowance rate of 100% in the first year, exempt from the half-year rule. The Agriculture Clean Technology Program provides non-repayable contributions (up to 50% of $2M) to support the adoption of clean technology by Canadian farmers and processors, to reduce carbon emissions.
For residential homeowners, the Canada Greener Homes Grant (up to $5000) encourages homeowners to make energy-efficient updates, including major retrofits and solar installations. Furthermore, the Canada Greener Homes Loan offers interest-free financing (up to $40,000) to help homeowners make their homes more energy efficient, and the Smart Renewables and Electrification Pathways Program provides direct financial support to organizations’ eligible renewable energy projects, including solar photovoltaics (PV).
Provincial and municipal solar programs also help Canadians affordably find the local means to go solar. For instance, Saskatchewan offers a program for homeowners who install solar PV to receive credits for excess power generated (7.5 ¢/kWh instead of the standard retail rate) and send power back to the SaskPower power grid.
So, how do metal roofs play into the equation?
Metal roofing provides an ideal platform for mounting rooftop solar. It is the only roof type with a service life (in the range of 50-70 years) that actually exceeds the service life of a solar PV system, which has an average of 32.5 years (and growing year-over-year). Most alternative roofing types will expire long before the life of the PV system, leading to the costly disassembly of the PV array, re-roofing, and re-assembly. Metal is also the most sustainable roofing type and is conducive to lower solar installation costs.
The standing seams act as inherent or cost-free “rails” for mounting solar PV.
These re-roofing and re-assembly expenses erode the otherwise attractive financial metrics of roof-mounted PV. High-end tile may be the only exception to the need for re-roofing, but its price tag is the same as standing seam metal roofing. Mounting solar to tile is invasive and very tricky to do without breaking tiles, so the cost is also much higher than mounting to metal.
Simply put, when all the facts are added up, the standing seam metal roof is the only roof type worthy of consideration for solar PV with face-attached metal profiles at a close second place.
The return on investment
Equestrian barn in Vernon, British Columbia integrates rooftop solar and snow retention.
When the decision is made to install solar, a new roof is often required. Metal roofing has become a driver for roof type selection in these cases as metal/solar roof systems may have lower initial costs than other roof system combinations and offer improvements in the lifetime return on investment (ROI). Therefore, the PV array and the roof should be regarded as a single asset.
When computing ROI within the solar pro forma, an inverter replacement is usually factored in at around year 15. Still, what about the cost of roof replacement? The solar array must be totally dismantled and then re-installed on the replacement roof. Factor in the inevitable cost of roof replacement and the advantages of a metal roof become clearly obvious.
Roof replacement is devastating to the financial proforma. A metal roof avoids replacement due to its long service life, which means it will still be going strong long after the service life of the solar array has expired.
Going solar in snow country
Metal roofing offers top performance in harsh climates because it remains durable even in extreme temperatures. This is important to consider as solar plays an increasing role in diversifying Canada’s energy mix. As such, heavy snow loads make integrating an engineered snow retention system critical to the planning and design of a rooftop solar array.
Solar panel frames are not designed to restrain a compressed blanket of snow. The image above illustrates damage from sliding snow.
Solar modules can inadvertently act as rooftop obstructions and default snow retention systems. PV module frames are not designed to restrain a compressed blanket of snow. If snow collects on the modules, the gravitational forces resulting from a rooftop snow blanket can deform and tear away the module frames. Without the ability to restrain the snow mass, thousands of pounds of snow can suddenly release from the roof causing damage to the modules and anything else below.
Integrating PV arrays and snow retention systems
When installing a solar array on a metal roof, it is important to note that gravitational forces will compress the snow toward the roof’s eave. This makes the eave the best place to install a snow retention system. A separation space between the lowest PV module row and the snow guards’ placement will allow the snow to naturally densify on the roof. The span of the separation space will vary depending on the geographic location’s snow loads and the size of the roof. If the lowest row of modules offers adequate separation space, lower-profile snow guards are usually sufficient. A taller snow retention system may be needed to contain the snow mass if the separation space between the snow guards and the solar array is minimal.
More information about the science behind rooftop snow loads and effective snow retention systems (like snow guards) can be found at “Snow Management on Metal Rooftops.”
Understand the PV Module’s Limitations
Another factor to consider is that accumulating snow may add significant weight to individual solar modules. Verify the modules have a design-load rating equal to or greater than the roof design snow load. Module manufacturers publish loads for any given module in their product information, but those figures may not have a factor of safety applied. Look for the “allowable” loads including the safety factors in the module manufacturers’ installation manuals. These manuals should also display the module’s appropriate mounting zones.
Adapting to the cold
As the investment in solar continues to grow in Canada, metal roofing’s durability and longevity are a perfect match for these renewable energy installations anticipated to perform for 30 years or more. However, the accumulation of snow on solar modules must be considered when adding rooftop solar in snow country. Understanding how snow loads affect a solar array will help ensure the PV system and the roof last for decades to come.
For more information and videos on this topic and more, please visit www.s-5.com.
About Rob Haddock
S-5! CEO and Founder, Rob Haddock is a former contractor, award-winning roof-forensics expert, author, lecturer and building envelope scientist who has worked in various aspects of metal roofing for five decades.
