Snow retention needed with solar panels on the roof

By Rocky Mountain Snow Guards.

Often overlooked, snow retention systems should definitely be considered with some rooftop solar panel installations.

Snow build-up on solar panels is different from other types of roofs. Snow compacts more and gets heavier, tending to slide off all at once, often needing special snow retention systems to prevent catastrophe. Wherever you have a solar panel on your roof, you need to consider the appropriate type of snow retention.

Slip sliding away

The team at Rocky Mountain Snow Guards has been involved in many projects where solar panels have been installed on existing homes. The need for snow retention below solar panels is often overlooked during the solar panel installation. Why? Because homeowners didn’t have any snow slide issues prior to the installation of the solar panels.

It’s pretty simple really. Asphalt shingles, tile and cedar shakes hold snow fairly well on most pitches, while the smooth surface of solar panels does not.

Less obvious are the problems caused by sliding snow. When most homeowners think about snow, they picture the fluffy stuff that falls from the sky onto the ground. It’s soft and usually not that heavy. Snow that slides off of solar panels is different. It’s compacted and heavy. And, most importantly, it tends to come off all at once. In the snow retention industry, that’s called a “catastrophic release.”

By the numbers

Consider this: On average there is 1.125 gallons of water in a cubic foot of snow. A gallon of water weighs 8.35 pounds. So, 12” of snow weighs 9.39 lbs per square foot. 

A typical solar panel array of 18 – 24” x 48” solar panels (144 sq. ft.) will have 1,352 lbs of snow in a 12” snow blanket. Drier snow weighs less but heavy snows may weigh twice as much. That’s over a ton of snow! If all of that snow releases at once, property below can be damaged and people or pets may get hurt, or worse.

What to use? When to use it?

So, when should a snow retention system be considered?

• When solar panels are installed on roofs where falling snow would drop onto decks, walkways, driveways, hot tubs, etc.  
• When falling snow may drop into window wells.
• When falling snow may block doors or low windows.
• When falling snow will drop onto a neighbor’s property.

If these conditions exist, it’s important to have the solar panels installed such that there is at least 18” of roof exposed between the bottom solar panel and the eave edge. This is where the snow fence will be attached.

Designed specifically for snow retention below solar panel installations on shingle roofs, the 12” tall, 4-pipe aluminum Drift Solar snow retention system ensures no snow slips past the snow fence. It serves as a “catch basin” for snow. The system comes in Mill Finish Aluminum or Coated Aluminum.

“The key is to protect people and property from snow accumulating below the solar panels as they keep working,” says Lars Walberg, president of Rocky Mountain Snow Guards. “With the Drift Solar Snow Fence System, the snow is held back and released gradually.

“Our snow fence systems are custom designed for each project. We make sure there is no shadowing of the solar panels. This helps ensure that once the snow releases from the solar panels that electricity production proceeds at the highest possible rate during winter conditions.”