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Sunday, April 17, 2016

Roofs can handle the weight

Study shows most US roofs can support a solar system
From Sandia National Laboratories. 
video world go inside solar
Most U.S. rooftops in good repair can take the weight of solar photovoltaic (PV) systems. That’s the conclusion of a three-year study by a research team led by Sandia National Laboratories.

“There is a misperception in the building industry that existing residential rooftops lack the strength to carry the weight load of rooftop solar photovoltaic installations,” said Sandia structural engineer Steve Dwyer. “Most existing well-built wooden rooftops can support PV system loads.”

Sandia took on the job of analyzing rooftop structural strength to address concerns raised in the U.S. Department of Energy’s (DOE) Solar America Cities program. The agency named 25 cities to promote adoption of solar technology at a comprehensive, local level through photovoltaics.

At least one city reported the primary barrier to solar was the difficulty and cost of obtaining construction permits for rooftop solar installations because of structural issues. 

“I couldn’t believe it was a problem,” said Dwyer, who led the Sandia test team. “Solar PV systems represent little additional weight and roofs are very strong.”

He said many code officials aren’t familiar with solar technology and lack the training to evaluate how a solar PV system might affect roof structure. 

So they bring structural engineers into the permitting process, adding time and money for the system owner and the solar contractor. 

Often, they then deny engineering certification for solar PV installations on wood roofs, declaring the structures too weak.

Read more at Sandia Labs.