*Wind map images used with the permission of the Applied Technology Council (ATC)

After years in the making, The American Society of Civil Engineers’ latest set of guidelines, ASCE/SEI 7-16, has now taken effect. These guidelines set forth a number of changes which contractors should take into account when designing and installing residential and commercial solar projects. The ASCE standard is referenced in the 2018 International Building Code (IBC) and International Residential Code (IRC), so the implications are far-reaching.

“It’s a big advancement in code development that will have a positive impact on the solar industry,” says Jon Neal, a product development engineer at Unirac. “The biggest changes are to seismic and wind loads, as ASCE 7-16 introduced prescriptive methods related specifically to solar in those areas.”

The newest standard ( was accepted in 2016 and has been fully adopted by a number of states as of January 1 this year.

ASCE is an international organization with more than 150,000 members and is the world’s largest publisher of civil engineering content and an authoritative source for codes and standards that protect the public. The changes are part of an ongoing review process that is intended to standardize the current wide range of approaches by designers, engineers, and manufacturers who are dealing with ambiguities in the previous code. Solar is among the undefined areas in the previous code that the new guidelines will attempt to clarify.

“Having solar called out specifically by ASCE will help provide standardization and consistency,” Neal says. “Everybody wins when the answers are more clear.”

At the same time, being unfamiliar with the new rules could result in costly delays or rejections in the permit process.

“These changes touch on just about every aspect of the solar planning process,” Neal says. “New wind maps alone mean nearly everyone will have to adopt some new design criteria. Otherwise, it’s hard to say how the overall changes in the code will impact an array design without getting into project specifics. For some pitched roof projects, for example, the new code could result in changes to rail spans. In other cases, there may be no change. The good news is, your partners in the industry should be up on this already and ready to help you fill in the blanks.”

Major changes this year include:

  • New wind maps that include more-granular details of the United States, including the first specific maps for Hawaii. Neal says the new maps are the biggest change for most people. “The old maps were basically just a big blob for the interior of the country,” he notes. “Now, wind values are specific to many more places, including unique values for Hawaii for the first time. Maximum wind loads will actually drop in the new maps for a lot of areas, but overall loading may increase because of other changes in the code.”
  • New, more localized seismic values that will have regional impacts. Some ballasted systems may require greater setbacks, for example.
  • Guidelines to specifically address wind pressure on solar panels installed parallel to roof surfaces of all roof slopes and wind pressure on solar panels tilted up from the surface of low-slope roofs.
  • Additional uplift factors for leading edges for every array—not just roofs. This “edge factor” means that every panel in a smaller array may ultimately have to be considered exposed and thus require new calculations.
  • Changes to roof zones (both hipped and gabled pitched roofs now have a number of subcategories for corners, pitches, and edges).
  • Formalization of high-altitude reductions for wind pressures and changes to snow maps.
  • New rules for buildings with roofs over 60 feet high that had previously been exempted.

Brandon Carrasco, Director of Customer Solutions for Unirac, notes that roof height change is just one of the reasons commercial as well as residential installations will have to take the new rules into account.

“We’re looking at a major revision here,” Carrasco points out. “There are updates to wind tunnel test reports that could impact ballasted projects too—ballast may increase in some cases and decrease in others. Also, there are new parameters in algorithms used to calculate loads. And that’s really just scratching the surface.”

For installers, he says, the big takeaway is awareness: “If you filed for a permit under the old code, you can proceed, but for new work, check your state’s code to see if it has changed. Make sure, before you get to the roof and if you’re using someone else’s design, that the design has taken these revisions into account. And new layouts might be different than what installers are used to, crews should be careful not to go on autopilot and start drilling pilot holes until after closely reviewing the plan set.”

An installer’s best bet for questions about wind speeds and snow loads is to check with the authority having jurisdiction (AHJ), but there are also some free tools available that can help. The beta website,, is a good resource and is maintained by the nonprofit Applied Technology Council (ATC). To minimize impacts if you’re doing your own design, reach out to a trusted partner. Though they may seem daunting, changes like these are part of the cycle, Carrasco says.

“It takes work to keep up with the changes, but we’re prepared and will work with our installers to make sure there are no surprises,” Carrasco says. “We have a whole group of engineers and solar designers here whose job it is to know this inside and out in order to offer up the best assistance.”

For help with system layout, engineering questions, and even permitting sets, you can reach Unirac’s Commercial Services team at (505) 248-2701 or via More information is available at