Rooftop solar makes tremendous sense. Underutilized rooftop assets are a perfect platform for deploying distributed solar generation facilities where power is most needed - under the roof.

That's what Jamie Hahn, managing partner at Solis Partners, a leading developer and integrator of commercial solar power systems based in Manasquan, N.J., had to say during a panel discussion on commercial rooftop solar at the PV Power Generation Mid-West and East Conference held recently in New York, N.Y.

"Rooftop solar is an ideal sustainability enhancement especially as owners and tenants are showing a distinct preference for green buildings," said Hahn. "Smart property owners are driving sustainability into their portfolios. The combination of reduced operating costs and more satisfied building occupants translates into higher occupancy rates, higher rents and faster appreciation."

PV Power Generation Mid-West and East provided an in-depth look at expanding large-scale solar power generation in the Midwest and East, where photovoltaic (PV) project development is on the increase due to favorable state incentives. The conference brought together local utilities, state regulators, grid operators, land and building owners with the solar community.

Other panelists and speakers included representatives from the N.J. Board of Public Utilities, the U.S. Department of Energy and the U.S. Environmental Protection Agency.

Hahn went on to highlight the market potential, the benefits, the design considerations and the challenges of commercial rooftop solar power generation systems. Citing figures from the National Renewable Energy Laboratory, Hahn outlined the exceptional market opportunity for commercial rooftop solar in the United States - the nation's more than 3.25 billion square feet of flat commercial rooftops hold the promise of generating over 150 gigawatts of solar.

New Jersey, where Solis is located, is now the nation's top commercial solar market in the nation. New Jersey is also the nation's second largest solar market, overall. Through a combination of attractive state and federal incentives, New Jersey has installed roughly 11,700 solar projects totaling approximately 450 megawatts of solar.

Although rooftop solar makes tremendous sense, companies considering it have to be careful to use reputable and experienced integrators, Hahn noted. "There are many instances where building owners are having their roof warranties voided due the fact that the installer did not implement the proper remediation measures required by the roof manufacturers," he said.

One of the most important considerations when installing rooftop solar is the condition of the roof and the warranty term remaining, Hahn noted. "Even though roof upgrades add costs and complexities to a deal, you are doing the right thing for the building owner by protecting their most important asset, the building."

"Owners need to understand that the roof system will act as the foundation to a 25-year asset," said Hahn. "If you are faced with the need to decommission a system, the true cost would be significant when you factor in the lost revenue recognition from the sale of electricity and SRECs."

Hahn also noted that there are a number of factors that have to be taken into consideration when installing a rooftop commercial solar system, including structural adequacy, expansion and contraction issues, thermal stress, and deviations to existing water run-off and snow drift characteristics on the roof. Additionally, careful consideration should go into the design, including optimal tilt access, orientation and shading, Hahn said.