What’s a fire setback? Why does it matter for solar installations?
When we look at a rooftop for solar, the goal is to replace as much of the customer’s current power use with solar as we can. However, all installers must obey certain rules when designing solar PV systems. One of the most important considerations in design is to comply with fire setbacks.This is a requirement imposed by the 2018 International Fire Code Section 1204 and adopted by the Authority Having Jurisdiction (AHJ) (i.e. City of Las Vegas, Henderson, North Las Vegas, or Clark County, etc.) Fire setbacks are distances that solar panels must not be placed within – mostly near ridgelines or peaks/valleys on the roof or other obstacles like skylights and chimneys – to allow fire fighters to safely walk on the roof when responding to building fire. Why do firefighters need a clear path on a solar roof? During a blaze, they will sometimes punch a hole in the roof in order to allow hot gasses and smoke to escape so that other members of the team can enter the building to pull people or pets out. This venting can also prevent an explosion since hot gasses can escape instead of building up pressure. The clear paths created by fire setbacks protect our first responders while they are working to save your life and your property during a fire.
In NV, solar panels cannot be placed within 3 feet (36″) of the ridgeline and must have 36” clearance from the edges of the roof (except the bottom) and 18″ from any peak or valley in the roof. (These are the rules for Clark County specifically, however all the jurisdictions here use the same setbacks.) On a flat roof, the panels must have 36″ around all edges and 18″ around any obstacle such as a sky light or air conditioner. Furthermore, the City of Las Vegas will not allow ANY roof vents to be covered by solar. No installer can ignore those fire setbacks and pass inspection, however we see many designs from other solar installers that are uninstallable.
Same House, Two Very Different Designs.
Take a look at the two designs for the same home shown above. The image on the left cannot be installed due to many breaches of fire setback rules. You can see panels touching the peaks and valleys on both sides of the array where there should be an 18″ clearance on BOTH sides. You can also see where the panels are not 36″ from the main ridgeline.
The image on the right shows the panel layout that can actually be installed on this roof. You’ll notice that only 15 panels will actually fit on the desirable South slopes when fire setbacks are properly included in the design. The remaining panels have to be put on the West slope.
Why is the other installer showing this “impossible to install” design to a customer?
It could simply be inexperience with fire setbacks or possibly incorrect scaling when the image was imported into the design software, however it is most likely that the installer is trying to show the customer a “best case scenario” with all the panels clustered on the South facing slope. (Panels on the South out perform those on the East, West or North slopes by a considerable percentage.) If all 22 panels could be placed on the South slope, it would produce 13,207 kwh. The actual annual production of this system as it can be installed with 17 panels on the south and 5 on the West is 11,494 kwh. That is 1,713 fewer kwh than promised or $205 LESS value of power per year (1,713 x .12/kwh=$205).
Ignoring fire setbacks on designs misleads customers into thinking they will get more production. It also leads to angry customers.
On this rooftop, placing them all on the South while ignoring fire setbacks not only inflates the estimated production for the system, it also misleads the customer on what to expect on install day. By the time it is installed and the installer has relocated panels to comply with fire setbacks in order to pass inspection, the customer is often not even told about the drop in production. If they are, it is far too late for them to do anything about it. Then, when the after solar bills come and they are bigger than the customer was led to believe, they have no recourse but to make a complaint to the Nevada State Contractor’s Board.
The moral of this story: Know what fire setbacks are and make sure your solar contractor has accounted for them in their designs from the get go.