Algae Resistant Roof Shingles

Learn About Shingles That Resist Moss and Algae

For roofs that either get a lot of shade or are constantly battling humid and hot conditions moss and algae can be a problem. Algae and or moss often show up on the east facing side of the roof but can also show up on other faces as well based on the amount of shade, heat, and humidity.

There are a few options to preventing the algae or black streaks from appearing on roofs. The most efficient options involve algae resistant roof shingles. This article is going to talk about the details regarding these types of shingles.

*If you also need help with cleaning your vinyl siding click the link to the left, to read our entire how to guide.

Algae resistant shingles are specially made shingles that prevent algae growth. They look like normal shingles and to the naked eye seem to be the same but they are manufactured a little differently. The most effective AM shingles now have copper granules embeded in the asphalt shingle along with the normal granules. These copper granules are strategically embeded within each shingle itself to ensure that the entire shingle roof is protected and so that the roof keeps its uniform color and look.

“An active ingredient in many AR shingles is titanium dioxide.” (Michael Slatter of Roofer Mike Inc)

* Pictures provided courtesy of Roof-A-Cide.

The idea to create asphalt shingles so that they could resist algae growth first began in the 1960s. In fact, the primary patent holder for algae resisting shingles is 3M and their patents go back to the 60s.

From the 60s till now the way AM shingles have been manufactured has varied. At first manufacturers tried to apply an algaecide coating to keep the algae from growing on the shingle. Later zinc was used to help prevent algae and moss growth. Zinc, like copper or aluminum, works but it was discontinued and is looked down upon a little bit because it can harm the environment.

Now the most common method of preventing algae growth on shingle roofs is by manufacturing the shingles with a percentage of copper granules in them. A common percentage of copper granules is roughly 10%.

Since their inception algae resistant shingles have continued to grow in use and popularity. In some states and counties, such as Miami Dade County algae resistant shingles have been code since 1992 after Hurricane Andrew. (Michael Slatter of Roofer Mike Inc)

When home owners first start seeing black streaks on their roofs many wonder if there roof is being damaged. To all those who wonder if algae or black streaks shorten the life span of your home the answer is no. Algae growth is purely a cosmetic problem. However, moss and algae sometimes get mixed up and confused. Moss can cause damage which could harm your home and roof. Read this article on removing moss on roofs to learn more about moss, removing it, and how it affects your roof.

Although “algae discoloration is primarily an aesthetic issue, it does have a negative impact on overall property values. This also makes it a monetary issue if you’re trying to sell a property or simply trying to maintain the existing value of the property. The actual algae growth or staining probably does not have a measurable impact on the life of the shingles, but when a light grey roof turns black, it’s going to draw more heat and increase cooling costs – or the overall ownership cost of the roof.” (John Browne of Roof-A-Cide)

“The AR shingles have been around for a while, especially in the South, but they have different expected performance periods with respect to how long they will keep algae from growing. Even though the manufacturers may give a 10 year or even lifetime warranty against algae discoloration, very few of them actually hold up for longer than five years in Florida and seven to eight as you move north. (When you read the fine print on the warranties, you’ll see that most offer a small rebate on cleaning when the algae starts to grow within the warranty period).” (John Browne of Roof-A-Cide)

Will algae resistant shingles actually stay true to their warranty? Each algae resistant shingle warranty will vary. It is important to read the fine print to fully understand each warranty. Another aspect to remember is they are called algae resistant shingles not algae proof. In fact, if AR shingles don’t see much sunlight they will not be able to resist algae for long. We have actually received confirmation from a certified professional roofer that if the humidity percentages stay at over 70% during the summer with very little to no sunlight hitting the shingles then the AR shingles will hold up just as good or “bad” in this case as shingles that are not AR resistant.

Hey everybody,

We are going social and have created a new Facebook group for people who want to know more about roofs, roofing problems, fixes, ask pros, etc. Feel free to join. It is a private group so once we get your request to join we will approve it as quickly as possible.

→ Join Here: Roofpedia Facebook Group!

Inspectapedia.com's article on Shingle Algae

Technical Advisory Buletin on Algae on Shingles by GAF

David Dodson from Rampart Roofing in Frisco, TX

Pictures of black streaked roofs provided courtesy of Roof-A-Cide and other information within the article is credited to John Browne of Roof-A-Cide.

Michael Slattery shared his knowledge on AR shingles based on his experience with them in Miami, Dade County as the owner of Roofer Mike, Inc

We would like to thank Mark Rothbauer, who is the CEO of Elite Claims Management in Colorado Springs, for the information shared with us during our phone interview. Mark is a professional roof adjuster who understands the ins and outs of roofs.