When designing the solar layout for your metal roof, it’s important to carefully plan the placement of the modules to harness the sun’s energy. For roofs located in areas with heavy snowfall, precise calculations are needed to resist “drag loads” and also to reduce the risk of rooftop avalanches.
Dueling Designs
Snow retention systems are engineered to allow accumulated rooftop snow and ice to melt slowly, rather than sliding off en masse, which can cause catastrophic damage to people, property and solar arrays.
Problems arise, however, when solar panels are installed too close to the snow retention system. They can inhibit the performance of the snow guards, allowing dangerous ice and snow to fall off the roof in an uncontrolled manner. Similarly, if snow guards are installed adjacent to and elevated above the lowest row of solar panels, they run the risk of casting a shadow and impacting the photovoltaic (PV) system’s performance.
A common issue arises when solar installers cover as much of the roof as possible with PV. They lay down modules from end to end and eave to ridge, leaving no roof space for the snow to effectively engage the snow guards. The best solution is to design and plan a space between the solar panels and snow guards to allow them to work together effectively. Plus, this space allows emergency rescue personnel to access the rooftop during a fire or other disaster.
Proper planning and design are critical to the success of rooftop solar and snow retention systems.
Designing an efficient snow and solar system can be challenging, as solar installers typically lack the experience of roofing contractors, and vice versa. It’s important to design a PV array and snow retention system to perform efficiently together. Unfortunately, this doesn’t always happen. If, after the initial solar installation, modules need to be removed to make room for the snow guards, the redesign and rework of the established electrical system is expensive and time-consuming.
What’s the Solution?
Thankfully, a load-tested, engineered snow guard system that is only a few inches in height can restrain a rooftop snowbank. For PV arrays in areas that experience heavy snowfall, solar installers should leave approximately 15% of the roof surface, from eave to ridge, for required roof space between the array and a dedicated snow retention system downslope.
Early collaboration between installers, architects and roofing contractors is key and can often mitigate system performance hurdles down the road.
You can install snow guards and solar panels using non-penetrating clamps that attach directly to the roof panel seam. This leaves the watertightness of the roof intact and doesn’t void the manufacturer’s warranty. On exposed-fastened metal roof profiles, a snow guard system can rely on brackets that have passed ASTM E2140 – “Standard Test Method for Water Penetration of Metal Roof Panel Systems by Static Water Pressure Head” – which verifies that the sealants on the brackets effectively prevent water penetration.
Bracket with factory-applied EPDM rubber undergoing ASTM E2140 testing.
Ideas To Hold On To
When done The Right Way™, combining solar and snow retention creates a high-performing, reliable rooftop solution. Roofing contractors, solar installers, architects and other project members must work together to design a solar-metal roof with snow retention.
Sourcing engineered solutions that have passed the industry’s toughest standards for load testing and watertightness ensures a reliable system that will perform for the life of the roof. Selecting high-quality products with proven performance can prevent potential design issues and reduce future labor and material costs.
Have you enrolled in S-5-University™? Learn from the Metal Roof Experts™ and discover best practices for installing solar on metal roofs.
