When you get past the cost, solar panel installations seem pretty straight forward. Call a company; they install the system, and in no time, you’re saving on your electricity bills. But there’s more to it.

Before a solar system can classy-up the joint, you need a structural assessment—especially if you are planning to install the system on commercial property. Didn’t know that? Don’t worry; you’re not alone.

“I have found that as a structural engineer, the blank stares tend to come with the territory,” said Adam Denton, structural project manager at EVstudio, an architecture firm in Colorado and Texas. “In all seriousness though, I do feel that this is one of the lesser known steps for people outside the industry.”

Typically, only large solar installers have an in-house structural engineer. Many companies still tap outside firms, such as EVstudio, during that stage of the installation process.

Denton and EVstudio has seen an increase in structural assessment demand in line with the growth of the solar industry.

“About three years ago there was a large increase in volume as more individual home owners wanted to take advantage of tax credits, increase the value of their home and save some money on energy costs by purchasing photovoltaic and hot water solar systems,” he said.

According to Denton, when solar wasn’t such a hot-button issue, city and town building departments weren’t familiar with the products. The solution: departments simply mandated that every potential solar installation required a professional engineer’s structural assessment.

“As the years have passed, building departments have become more familiar and developed a comfort level with solar installations; many have retaken the responsibility of structural assessment in-house in an effort to increase revenue in a tough economy,” he said. “There are still many jurisdictions that require structural assessment for commercial solar installation, but far less that require it for residential.”

While the relaxed policy for residential buildings does make installing solar an easier process, there is a lot at stake.

“A lot of sales people soothe customer’s fears of how an array is going to affect their building by telling them that the panels only weigh in the neighborhood of three pounds per square foot,” he said. “While this is true, most overlook the fact that the panels are mounted to a rack that in turn mounts to the roof through small footings.”

And these footings, essentially, become “point loads.” Think of it this way: When someone breaks through an iced-over pond, we’ve learned that the safest way to get them out is to lay flat on our stomach and attempt a rescue. That’s because when we are upright, our feet are, ostensibly, point loads. The ice can potentially support our weight when it’s distributed over a larger surface, but standing up, and concentrating all our weight onto two points, would most likely result in a cold bath. So a solar array's weight, like the above example, is concentrated on the points that connect it to the roof.

“This scenario is exacerbated when the panels are loaded with snow,” said Denton. “For example, only considering the weight of snow, I have run into several situations where the calculated structural capacity of the roof framing members would have been able to support the uniform load but were inadequate when that same load was converted to concentrated point loads.”

According to Denton, the above example isn’t common. Down loads, as he calls them, are not the biggest red flags when it comes to a rooftop array.

“What truly concerns me as a structural engineer is the uplift loads created by the wind,” he said. “I am not so concerned about the net uplift load on the building’s structure, but being able to develop a strong enough mechanical connection to keep the panels themselves attached to the roof.”

When a system isn’t properly installed to withstand wind gusts, the situation is potentially life threatening.

“The possibility of an array tearing off a roof would not only mean the loss of several thousands of dollars in solar equipment, but is a real life safety issue,” he said. “I have heard a rumor from more than one source that an installer in Jefferson County attached the footings of an array only to the sheathing of a residential home, and one day, the array tore off the roof and struck a neighbor’s home.”

Denton said that the typical screws used in commercial installations are not strong enough to hold the array in place if they are simply attached to the roof sheathing alone. The uplift risks are far too high in that scenario.

Again, a structural assessment is not required of all projects, but, according to Denton, that doesn’t mean it isn’t important for every solar installation.

“I will stress that it is always a good idea to have a registered professional structural engineer’s evaluation for every installation,” he said.

And although it may seem like an added cost to an already expensive project, your neighbor’s house will thank you when your roof doesn’t come crashing down.

EVstudio has offices in Colorado and Texas, but accepts out-of-state jobs as well. Please visit EVstudio.info for more information.

Pictured: Ben Jones and Chris Hamilton of Vibrant Solar check the underside of a recently installed solar array in Fowler, Colo.