Solar Panel Snow Retention With Roof Snow Fences

A large part of our business is designing snow retention systems for homes where solar panels have been installed on existing homes.  The need for snow retention below solar panels is often times overlooked during the solar panel installation 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 pretty 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 tends to come off all at once.  In the snow retention industry, that’s called a “catastrophic release”.  

Consider this:  On average there is 1.125 gallons of water in a cubic foot of snow. A gallon of water weighs 8.35 lbs.  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 spring 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.

So when should snow retention 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.

This photo illustrates our snow retention system at work on a residence in Boulder, CO.  The snow fence is installed on the portion of the roof above a driveway.  You can see how the system held the snow while the snow on the back portion of the roof was allowed to slide off.

For more information, please contact us at info@rockymountainsnowguards.com.