Install tip: Use relaxed fire pathway codes to build bigger arrays on roofs

This installation tip was provided by Jeff Spies, president, Planet Plan Sets; codes/standards chair, California Solar and Storage Association

Credit: Dennis Schroeder/NREL

A few years ago, many solar installers were caught off-guard when code updates introduced fire setbacks and pathways for roof-mounted PV installation. Building departments in California, Arizona and other states enthusiastically enforced requirements for 3-ft setbacks from the ridge and two pathways up each roof surface with PV for most residential systems. These requirements were intended to help firefighters vertically ventilate roofs during a fire.

Thankfully, the code did allow local fire chiefs to waive setbacks and pathways entirely if vertical ventilation would not be used. In recent years, a growing number of fire chiefs have determined that vertical ventilation is inferior to horizontal ventilation for clearing smoke, fumes and heat in a fire. As a result, significant variations exist nationwide in implementation of pathways and setbacks.

Some fire officials waive setbacks and pathways entirely, others modify the rules to be less onerous, while some very conservative AHJs impose even more stringent requirements.

The latest International Codes (I-Codes) have officially relaxed the requirements. Now most residential projects only require an 18-in. ridge setback and a single pathway up each roof surface. These new “modified setbacks and pathways” went into effect in California in July 2018, and solar installers rejoiced in the ability to reclaim valuable space for larger PV systems.

There are four major variables that dictate whether a roof qualifies for the relaxed setbacks and pathways:

1. Percentage of roof coverage by PV
2. Access of pathway location from adjacent roof surfaces (including step-up dimensions)
3. Location of the PV array on the house (street or driveway-side access is best)
4. Presence of fire sprinklers

While there are more variables to consider, I estimate 75% of residential PV installations will benefit from these relaxed setbacks and pathways, allowing larger PV systems to power ever-growing electricity loads.