Nothing ruins curb appeal like unsightly black streaks marrying your roofline. Houses in climates with frequent rain and humidity are at higher risk of experiencing roof staining due to algae. The best roofing manufacturers offer algae-resistant products that prevent these unattractive issues.
How can shingles become algae-resistant? Keep reading while we take a deep look at Algae Resistant.
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Algae Resistant Shingles - What are They?
The name algae resistance gives an easy explanation for the purpose and features of special shingles. Algae Resistant shingles prevent the growth of algae, meaning your roof stays clean and attractive.
So, how do algae-resistant shingles work? You wouldn't be able to tell that a shingle is Algae Resistant when looking at it attached to a roof. These types look exactly like shingles without algae resistance. The difference is in the manufacturing process.
The best AR shingles have copper granules mixed in with the regular granules - tiny particles that top the asphalt construction. These embedded granules keep the shingles stain-free while also preserving the shingle's uniform look and color. Copper acts as a poison for algae, which feed on the limestone inside asphalt shingles.
Why is Algae Bad for Your Roof?
Algae, scientifically known as Gloeocapsa Magma, is a tiny blue-green organism that turns black as it starts to grow on unprotected roofs. Roofs that get a lot of shade, warmth, and moisture with little sunlight to dry the shingles out are at the highest risk for algae growth, as these are prime growing conditions.
Most algae start at the top of the roof and spread down towards the edge, causing black streaks. Issues stemming from the presence of algae on a roof include reduced home value, less curb appeal and appearance, and increased energy costs.
Light-colored roofs often have better energy efficiency than darker roofs. Because algae will look black on any colored roof, it blocks the reflective properties of the shingles. This issue causes the shingles to absorb more heat, increasing cooling bills during hot months.
In the beginning, algae growth doesn't have a severe effect on your roof, besides looking unkempt. But over time, the algae eats all of the limestones, leaving the asphalt weak and at risk of damage.
Algae can also host fungus that causes a more severe problem - lichen. Lichen is harder to get rid of and can cause more damage to your roof than algae. Once lichen forms, moss is sure to follow. If moss starts to grow on your roof - literally because moss produces roots that burrow under the shingles - you can end up with significant problems.
Once moss grows roots, your roof can be at risk of mildew, bacteria, and mold due to the extra dampness - moss and the roots absorb water. These roots will expand when frozen during winter, which can cause your shingles to crack.
And finally, moss can eventually create a layer of soil on your roof. Wind-blown seeds from nearby foliage can land on the soil and sprout.
Although you might not have heard of algae resistance, it's not anything new. As a matter of fact, algae resistance patents date back to the 1960s - 3M filed the first patent.
The design has evolved since the first creation, with multiple big-name manufacturers carrying one or more lines. In the beginning, producers used a coating of algaecide. Then, manufacturers tried using zinc. Although it prevented moss growth and algae, zinc became discontinued due to being harmful to the environment.
Today, almost all algae-resistant shingles are due to the use of copper granules, roughly 10% or less. Some states and individual counties have codes that require the use of AR shingles - the Miami Dade County made AR shingles code in 1992, following Hurricane Andrew.
Are Algae-Resistant Shingles Necessary?
As we just mentioned, there are locations where it might be required for you to use shingles with built-in algae resistance.
But if there are no requirements where you live, using AR shingles is optional and not necessary. Having black staining on your roof from algae can be unattractive. But these stains, nor algae itself, will harm your roof. However, as we described above, algae can be a gateway for further issues like lichen or moss growth.
If you choose not to use an algae-resistant shingle, you won't experience a shorter lifespan or failed components. Your roof will last as long as the manufacturer outlined, regardless of stains. But, the staining can lower your home value, an issue if you plan to sell your home.
However, moss, which is sometimes confused with algae, can cause damage to your roof. As moss grows and thickens, it can cause the shingles to lift, posing the risk of water or wind damage. And moss buildup can also trap debris on the roof, possibly leading to leaks or rotting.
Who Makes Algae Resistant Shingles?
Almost every reputable asphalt shingle manufacturer offers at least one line of shingles with built-in algae protection. Below is a list of some of the most popular lines.
- GAF - StainGuard technology (limited warranty)
- Atlas - Scotchguard 3M technology (lifetime warranty)
- CertainTeed - StreakFighter technology
- Owens Corning - StreakGuard technology
- Malarkey - Streak Resist technology
Although many brands have algae-resistant lines, take the time to review the warranty for this protection. Many manufacturers have a short term of 10 years, while other brands list their AR as lifetime protection. Due to the vast variation, it's crucial to review warranties before choosing a product.
Despite the listed warranty time, many products start to fail within five to eight years. The further south you live, the shorter the AR will last. Lack of sunlight can also cause the AR to fail, leading to the presence of algae.
Some brands list rebates for algae cleaning if your roof starts to grow algae before the AR warranty expires. If you live in a climate with moderate to heavy amounts of rainfall, humidity, or other causes of your roof staying wet, you'll want to pick a product with the most extended AR protection.