Metal roofing offers top performance in harsh climates because it remains durable even in extreme temperatures. The ideal platform for rooftop solar photovoltaic (PV) arrays, metal roofing has a 60+ year lifespan making it the only roofing type able to outlast the service life of PV systems. This is good news as solar plays an important role in diversifying Canada’s energy mix.
Solar Is on the Rise
Executives in Alberta at BayWa r.e. Solar Systems see solar energy installations increasing across Canada. BayWa is a globally active group within the core segments of energy, agriculture and building materials, and BayWa r.e. Solar Systems’ CEO Réal Bouchard says solar energy is a fast-growing sector.
“Companies are more conscious of their carbon footprint, and many have departments focused on sustainability,” Bouchard notes. “With the ability to write-off a percentage of a solar array’s value as a rapidly depreciating asset, corporations also have a tax incentive for going solar.”
According to a Canada Energy Regulator report, “Economics of Solar Power in Canada,” businesses in many provinces can expect to save money by installing solar.
As winter approaches, snow creates special considerations in relation to rooftop solar panels.
Ensuring Reliable Snow Retention
Accumulated snow on metal rooftops produces unique conditions making snow retention systems imperative in regions with heavy snowfall.
Solar panels can act as rooftop obstructions and create unintentional – and unreliable – 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 may suddenly release from the roof causing damage to the modules and anything below.
Learn about the science behind rooftop snow loads and effective snow retention systems (like snow guards) through “Snow Management on Metal Rooftops.”
Proper Integration of a PV Array and Snow Retention System
When installing a solar PV array on a metal roof, it is important to note 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.
The “Moment Arm” Created
Apart from the foregoing, it is also important to never stack components when mounting solar PV attachments. While using only one L-Foot is a best practice in any region, it becomes even more critical in snow climates. Double stacking forms a moment arm and creates a “prying” force, which could result in a failure of the mounting system and roofing attachments as snow accumulates on the modules. So, the lower to the roof the module glass is—the better.
Know the PV Module’s Limitations
Another factor to consider is accumulating snow may add significant weight to individual solar modules. Verify the PV modules have a design-load rating equal to or greater than the roof design snow load. Module producers publish loads for a 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 producers’ installation manuals. These manuals should also display the module’s appropriate mounting zones.
Hidden Snow Loads and Tilted Racking
Tilted racking systems create a unique challenge. Typically mounted on low-slope roofs, each PV module row is angled toward the sun for better power production, requiring space between rows to prevent modules from shading one another. This space creates an area for wind-driven snow to stack up, which may result in surplus loads unanticipated in roof design.
The trapped snow or ice in the literal shaded areas may not melt or “wind-scour” (aerodynamic shade), aggravating the problem. These areas of aerodynamic shade can lead to accumulated snow loads exceeding what the roof was designed to carry. The ASCE library offers information on how to manage aerodynamic shade and wind-driven snow in the report, “Snow Loads on Solar-Paneled Roofs.”
Help Solar PV Panels Survive Snow Climates
Solar PV arrays are gaining popularity across Canada, and metal roofing’s durability and longevity are a perfect match for these renewable energy installations anticipated to perform for 30 years or more. Snow accumulation is an important factor when adding PV modules to any roof in snow country. Understanding how solar panels are affected by snow loads 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.
Join S-5! in Toronto at Electricity Transformation Canada – (CanREA) on November 17 – 19 and again at The Buildings Show 2021 on December 1 – 3. S-5! will showcase innovative solutions for mounting rooftop solar PV modules and reliable snow retention systems, and company experts will be available to answer questions.
