Photovoltaic Roofs: Questions About Economics, Physical Structure
Before going forward with the design and installation of a PV system, managers must answer a series of important questions regarding the physical feasibility and economics of installing the system:
- Does the orientation of the building and roof take full advantage of the sun?
- Is the roof area clear of shading from trees or other buildings, which would reduce the amount of sunlight reaching solar panels?
- Is there enough area on the roof to install the system without restricting access to rooftop equipment?
- Can contractors install the system without restricting rooftop drainage?
- Does the PV system meet fire, wind, and snow- and seismic-load requirements of local building codes?
- Can the roof structure support the weight of the PV system?
- Will the roof itself last as long as the PV system? The cost of removing the PV system to replace the roof and reinstall the PV array could be enormous, so managers first must evaluate the condition of an existing roof or the desired performance of a new roof.
- Is a roof-system warranty in effect? If so, will installing a PV system affect the warranty?
- Can installers properly attach the PV system to the existing roof without damaging the roof system? Managers need to evaluate the potential harm from flashing or adhering PV systems to an existing roof system. Certain types of PV systems — specifically, building-integrated, thin-cell PV panels adhered to the membrane — have caused accelerated heat aging to some roof membranes to which installers adhered them.
- What type of PV system will best meet the organization’s needs — thin-film or crystalline? Each type has different benefits, so the choice depends on many factors, such as available area for panel installation, structural weight restrictions, cost comparison of panels, projected panel performance in the specific environment, support structure, roof type, drainage, roof age, and installed contractor base.
- How difficult is it to connect the PV system to the building’s electrical system?
- Are there local code or utility interface restrictions that might affect the decision on a system?
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