Photovoltatics: Roof Racking Systems
By Kevin Ernster and Eric Hasselbusch - May 2012 - Roofing
Crystalline panels require racking for attachment to the structure based on their frame design. The racking can attach to the building structure through the roof or by installing a ballasted rack system.
Before installing any type of racking system on your roof, managers need to schedule a structural evaluation and wind-load calculation to ensure the roof can support the extra loads.
Since amorphous panels are flexible, they typically are welded or adhered directly to the roof membrane. Due to the lighter weight of the system, structural and wind loads decrease. Managers also should be aware that codes require fire disconnects and safe fire lanes between panels.
When installing a rooftop PV system, the roof becomes more than just a watertight barrier. It becomes a work surface with increased traffic.
Managers should consider incorporating a roof-maintenance program that begins with designing a more durable roof system and focuses on identifying potential leaks and making repairs before leaks occur. Managers also should consider implementing operational controls, such as restricting roof access, maintaining a roof-access log, and implementing training for vendors accessing the roof.
The cost of installing a PV system has fallen dramatically in recent years, but available funding still might be a limiting factor. Current systems typically cost around $5 per watt. Although still expensive, managers should consider additional sources of funding that might reduce the overall cost to the facility owner.
Federal incentives for commercial businesses include a 30 percent tax credit on the total cost of the system and a five-year depreciation schedule, including a 50 percent bonus provided during the first year.
Many states and utilities also provide incentives and other options to consider that can reduce the payback period. Managers can visit www.dsire.org for more specific information on federal and state incentives.
Although recent setbacks in the PV industry have created short-term concerns, the technology's future looks bright. Taking time to establish goals, evaluating roofs condition and considering available PV options allow managers to make more informed decisions about incorporating PV as part of facility operations.
Kevin Ernster, RRC, is a senior consultant with Benchmark Inc., a national roof consulting firm with headquarters in Cedar Rapids, Iowa. Eric Hasselbusch is an account manager with the firm.