The Tesla Solar Roof is a product with two jobs. It must generate enough solar energy to power your home and maybe even put some extra energy into your Powerwall, or, barring that, send it back to the grid, hopefully for a discount on your energy bill. However, all of this extra power will not matter if the Solar Roof does not adequately perform its other job as a sturdy, dependable roof.
One of the things the Solar Roof needs to do is withstand high winds so that tiles do not get damaged. Tiles must remain intact so as not to allow rain to seep into the house after high winds. Tesla’s Solar Roof has been given a wind rating of Class F according to the ASTM D3161 standard test.
In order for a roof to be approved for use and sale, roofing materials have to go through a series of tests to be rated for how they withstand wind, fire, and hail. More than likely, your roof will face wind more often than the other two elements. Read on to learn all about Tesla’s Solar Roof wind rating and what exactly it means.
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Solar Roof Wind Rating Explained
While all are important, your roof comes into contact with the wind more often, on average, than hail and fire, so the Solar Roof really has to do well against the wind.
There are two types of tests used to determine a wind rating. Believe it or not, ASTM D3161 is the short version of the name of the appropriate test for the Solar Roof shingles. The long version means that the D3161 is a standard way to test the ability of typical roofing materials to resist wind that is induced from a fan.
The other kind of test is for sealed asphalt shingles, and it measures their resistance against the uplift force of a replicated wind. It is called ASTM D7158, but you only need to know that for reference. Tesla solar tiles do not fit into this test category.
But they do fit into the parameters of the first test mentioned above. This test method is used on a variety of shingles in order to determine what level of wind speed they can resist for a certain period of time. After the shingles successfully complete the test, they are given a rating:
- Class A
- Class D
- Class F
In order to achieve the rating of certain classes, they must withstand wind speeds that correspond to that class rating. The corresponding wind speeds are:
- 60 mph
- 90 mph
- 110 mph
Because Tesla’s Solar Roof is rated as a Class F in this category, that means it can withstand sustained wind speeds of up to 110 miles per hour. For reference, 110 miles per hour is at the top range of a category two hurricane.
Wind Rating Test on the Solar Roof
In order to understand a little bit more about what the wind rating is and what it means for Tesla’s Solar Roof, it is worth looking at:
- Materials that are tested
- How ASTM D3161 test is performed
- What it is meant to expose in the material
- What the test’s limitations are
All in all, the tests are valuable tools for discovering or verifying the classification of roofing materials.
And as such, the classifications enable consumers to understand in a clear and simple way how certain roofing materials perform in the general condition of high winds. You may not necessarily know what that means as far as the limitations of the test are concerned, so that will be discussed later as well.
Materials That are Tested
The ASTM D3161 is meant to be performed on certain kinds of roofing materials. The test used to have the words “Asphalt Shingles” in the title, but those words were replaced with “Steep Slope Roofing Products” in order to accommodate a bigger range of roofing materials, not just asphalt shingles.
These materials can include:
- Metal shingles
- Concrete tiles
- Cement shingles
- Photovoltaic shingles
The Tesla Solar Roof would qualify as photovoltaic shingles because Tesla’s roof shingles encase the photovoltaic sensors that are responsible for collecting solar energy.
There are some materials that are not included in this test, and those are the ones that would be tested under the ASTM D7158, namely: “Sealed Asphalt Shingles.” This would apply to roofing material that is continuous and sealed over the roof.
How the ASTM D3161 Test is Performed
At least two samples of the roofing material are attached to a surface that mimics the slope of a roof. The tester attaches the material in a way that is consistent with the design of the material and the manufacturer’s specifications for the material. The most exposure the material is given to the fan is about 16 inches at a slope of 17%.
So in the case of Tesla’s Solar Roof, at least two shingles, if not more, would have been set up just the way Tesla would install them on your roof. Except they would be installed on a test surface.
Once the material is set up, a fan is used to create the wind speed that the material is tested against. The fan keeps the wind speed direct and constant for two hours, and then it is turned off.
What the ASTM D3161 Test is Meant to Expose
While conducting the test, the evaluators watch the material, such as the photovoltaic shingles, for any changes that would indicate damage or lifting from the “wind.” If the material is damaged or has been lifted by the end of the test, then it has failed the test.
But if the material has no damage at all to it, and it has not lifted from the test surface to which it had been attached, then it has passed the test and will receive the classification it was tested for.
Limitations of the ASTM D3161 Test
While this may sound like a simple but thorough test, there are some limitations. This does not mean that the test is a fraud. It just means that some things occur in nature or in practice that you cannot replicate in a lab, so it is best to be aware of those things.
First, a fan cannot replicate what wind actually does. To put it another way, wind cannot blow as constantly as a fan. So in one sense, a fan is a more severe test by providing continual, unabating pressure at 60, 90, or 110 miles per hour. But in another sense, a fan cannot create the pressures of:
Second, the test cannot accommodate the fact that roofing material goes on a building. That may sound obvious but think about the complications an actual building creates. It can possibly change the effect of wind due to its:
- Width (how much of a barrier it creates)
- Any weird angles it may have
Finally, the test cannot account for any variances in how the shingles are installed. In other words, the classification may hold up against the wind, but it will not hold up against shoddy workmanship. This may include, but may not be limited to:
- Use of the wrong fasteners
- Use of the wrong adhesive
- Shingles that are misaligned
- Unusual roof slopes
- Dirt or debris that has gotten trapped under the shingles
Tesla’s Solar Roofs are covered by warranty. Solar Roofs are also installed by contractors working for Tesla, so any installation issues should be covered by Tesla’s warranty as well.
Now that you understand all that goes into testing roofing material according to the ASTM D3161 standard, you can begin to appreciate why Tesla’s Solar Roof shingles have the highest rating for that type of material, a Class F rating. It has earned the right to be a tough roofing material (not just in this, but in the other categories as well).
You can also appreciate the limitations of the test. There are settings both natural and man-made that the test simply cannot account for, such as the variance of wind speeds and building height, etc. The test also cannot account for any mistakes that are made during the installation of the Solar Roof tiles.