Strategically Green: Making Sense of Solar

Spring 2012

Which solar panel products are best-suited to install on commercial buildings? What are the pros and cons of these solar panel products from the vantage point of a commercial property owner? The Solar Technology Reference Guide, funded by the NAIOP Research Foundation, identifies the product characteristics, benefits and limitations of a range of solar panels on the market today.

Topics include construction and installation, as well as long-term operational impacts, maintenance, access, roof wear and breakage/environmental risks, to name a few. While the guide does not recommend any specific technology over another, it provides information to enable property owners to overcome their hesitancy to pursue projects and make informed decisions about what solar panels are right for their properties.

Solar Product Categories

The key to choosing appropriate products for a specific project is understanding the similarities and differences between available solar photovoltaic (PV) technologies. Current solar products on the market can be grouped into four broad categories based on their interaction with the host building:

Rack Mounted Glass PV Module Systems are the most common type of solar solution. They tend to be the heaviest solutions, but they enable optimum energy production and they can be customized for almost any roof condition. They often require large amounts of space on-site for staging and prep areas.

Composite Frame Glass PV Module Systems offer modular and pre-assembled solar module designs that support fast installation and lower total system weight. There are a limited number of manufacturers of composite frame systems. These types of products are becoming more popular on commercial roofs where there is a need to both minimize weight and expedite the installation process.

Adhered Building-Integrated PV Module Systems address weight-constrained rooftops and metal roofs that are difficult to accommodate with traditional solar module systems. These technologies are the lightest solar products on the market today. Energy production tends to be lower because they are installed flat to the roof, not angled to maximize the energy they capture from the sun.

Structural Building-Integrated PV Module Systems are highly engineered for custom applications and they tend to be the most expensive type of solar project. They offer solutions that are integrated into building components such as curtain wall facades, carports and overhead canopies.

Some key points to consider when planning a solar project:

Solar array weight can become a driving factor in the choice of which solar product is the most suitable. Solar modules typically weigh between 25 and 70 pounds and are designed to be carried by two workers on the job site. Few existing buildings were designed with solar in mind, so there is often little excess structural capacity to support solar equipment on rooftops.

Only a portion of a roof’s total area can be covered with solar panels. Panels should not be placed in areas shaded by tall HVAC equipment, adjacent buildings, penthouses or trees. Pay special attention to areas of poor drainage -- standing water can damage solar equipment as well as over-stress the roof. Also, panels should be placed so they do not cast shadows on each other.

There are two types of warranties that concern the real estate professional – materials and workmanship (five years) and energy output (25 years). Modules and inverters are typically warranted for 10 years, while racking is often warranted for five years.

Connecting to the utility grid is a factor that can affect the economic viability of a solar project. Solar project owners often need to undertake interconnection reviews in order to get approval from the local utility. At times the utility may require upgrades to the local grid system to accommodate the solar facility’s new capacity.

The solar industry in the United States is poised to continue its upward trajectory of growth in the years that come as more states adopt solar programs. It is widely acknowledged that not every solar technology will achieve commercial success. There will be success stories and failures along the way but this will ultimately lead to better products and drive even wider adoption.

For more information on this and other completed research reports, visit the NAIOP Research Foundation.