How to Clean Moss Off Your Roof and Solar Panels

Moss is a persistent plant that can grow if sunlight, dirt, moisture and some shading are present. In moist and humid climates, the surfaces of and roofing under solar panels are ideal places for moss, and things like algae and lichen, to grow over time. The soot deposited by forest fires combined with misty or rainy weather can also create the ideal conditions for moss to take hold and spread. Knowing the proper way to get rid of them so that you don’t damage your roof or solar panels, and potentially void any warranties, is important.

Prevention is Best

As with most conditions, if you can prevent plants like moss from taking hold on your roof it will save you effort, time and money, and protect your home longterm. Doing regular roof maintenance, like using a snow blower or broom to get rid of loose dirt and leaves, and rinsing your roof with a garden hose and nozzle sprayer once or twice a year, really pays off. But if it’s too late for preventing, here’s info on how to get rid of unsightly and damaging grime and plants.

Cleaning Open Roof Areas

To learn the best way to get rid of moss growing on a roof, we spoke with the professionals at S&S Roofing in Arlington, Washington. They informed us that newer, quality composition roofing will likely contain growth inhibitor to reduce if not eliminate plant growth. But if you have an older roof, or if conditions are just right, plant life may be able to grow.

S&S Roofing told us that the most effective method of cleaning algae, moss and dirt from a roof is with a 50:50 mix of laundry strength liquid chlorine bleach and water.

Cleaning Around and Under Your Solar Panels

The above method will work well for cleaning areas of your roof that do not have solar panels. However, bleach can damage solar panels so you will not want to use it near or under your array, or to clean off any plant life that attaches directly to the surface of your solar panels.

Instead, you can create a homemade cleaner for both your roofing and the panels themselves, using white household distilled vinegar. White vinegar contains acetic acid that kills moss and other plants. It is also a natural cleaner, so it can help remove dirt and grime at the same time.

Do’s and Don’t of Cleaning Your Roof

• Do use proper safety gear – a secured ladder, fall protection, safety glasses, and shoes with ample traction. Roof cleaning is slippery business. Keep yourself safe! Be sure someone else is around to help just in case you have an accident.
• Do use appropriate personal protective equipment for working with chlorine bleach.
• Do take proper precautions to protect landscaping and surrounding areas from the chlorine bleach or vinegar solutions when applying to roof. Bleach and vinegar are highly effective plant killers.
• Don’t use a pressure washer on a composition shingle roof. The high pressure on the shingles can loosen the granules and damage your roof. A garden hose sprayer is safe to use on your roof.
• Don’t clean your roof on a hot sunny day. Choose a cool and overcast but dry day.
• Do hire a professional if you have any question about whether or not you can safely and effectively perform this task.

How to Clean Moss Off Your Solar Panels and Roof – Step by Step

For roofing material:

1. Wet down the roof with plain water first, then apply bleach or household white vinegar mixture with a sprayer. The amount of mixture you will depend on the size of the affected area. If it is a small area use a spray bottle.
   • For new moss on a large area, use a 50/50 water and bleach mixture, or mix full-strength vinegar and water in a ratio of 1:2 and pour it into a sprayer. If the moss is severe, you can apply full-strength vinegar without diluting. Do not use full strength bleach.
   • If using vinegar, to help the mixture cling to moss and lichen add a very small amount of dish soap, about 1 ounce per gallon of vinegar and water mixture.
2. Let the solution sit for at least 20 to 45 minutes. For stubborn plant growth or staining you may need to leave the mixture on longer. However, avoid letting the solution fully dry as it may prevent complete rinsing.
3. Lightly scrub with a soft-bristle brush to remove the dead moss.
   • Be aware, brushing, especially on a dry and windy day, can easily spread moss spores to the surrounding environment, which means moss will likely grow back quickly if the conditions are right. That’s why it’s important to wet your roof before brushing.
   • Scraping or gentle brushing isn’t effective on its own because it may leave some moss in cracks and areas where the brush can’t reach.
4. Rinse off the roof with a garden hose/sprayer.

Cleaning around, under or on your solar panels,

5. DO NOT USE BLEACH ON, AROUND OR UNDER YOUR SOLAR PANELS
6. Refer to our info on Solar Panel Cleaning Instructions for specific instructions on cleaning and protecting your solar panels.

Additional Tips for Roof Cleaning and Discouraging Plant Growth on Your Roof

• There are commercial products available that are safe and effective at removing plant growth from your roof. But be sure they specifically state they can be used on solar panels before using them on your array.
• Prune any tree limbs that overhang the roof—natural sunlight is a powerful moss preventive.
• Debris that does begin to accumulate on the roof should be cleared regularly with a leaf blower or similar, non-abrasive method as part of a regular maintenance program.
• Keep gutters clean to ensure proper water drainage. Do not allow gutters from an upper roof to drain directly on a lower roof; extend the downspout from the upper roof into the lower gutter.
• Prevent future moss growth by installing zinc or copper on the roof just below the top ridge on both sides of the roof.

Have more questions about how to clean your roof? Your local roofing contractor is a great resource for professional tips.