Commercial Rooftop Solar: Common Technical Concerns
Commercial solar may be interpreted as rooftop solar for companies as opposed to rooftop solar for homes. However, commercial rooftop solar involves a variety of unique types of projects and customers. In addition to business size from local small businesses to large corporations, “commercial” rooftop solar customers can also include schools, universities, governments, and even nonprofits.
To facilitate decision making, the first step is to assess the technical suitability of the building for PV. The key considerations are shading, structural requirements, roof orientation, space requirements, utility interconnections, load/power factors, and considerations for carports. Also, business owners may want to consider the addition of energy storage to the building as part of the technical assessment. Energy storage can perform several relevant functions: Backup Power, Power Quality Management, and Energy Cost Management. As soon as a commercial
- How my building roof will be impacted by solar PV system installation?
A rooftop PV should not have negative affect on the roof if installed correctly. The business owners’ main concerns about commercial rooftop PV systems usually include the possible impact PV may have on roof integrity, building permitting, roof warranties, and business operations, however, all of these risks can be eliminated or mitigated, as outlined below. All rooftop PV systems should be designed and installed by reputable solar companies. Although national certifications are not required for PV designers and installers, many installers are certified by the North American Board of Certified Energy Practitioners (NABCEP).
- How are PV systems attached to the roof?
For commercial building roofs, there are two leading mounting techniques for PV systems: 1- Ballasted Racking which uses heavy weights, usually concrete blocks, to secure PV systems on a flat roof. These ballasted systems require detailed engineering reports and evaluations to ensure that the wind loading, and dead loading issues of the system have been properly addressed. 2- Attached Racking that uses roof penetrating hardware to mount PV systems on any type of roof. There are many types of attached racking systems for different applications. The number of required roof penetrations will depend on the roof structure, PV system design, and local building codes.
- How commercial rooftop PV system impact roof drainage, or maintenance of other rooftop systems?
The PV system will not impact other rooftop systems and drainage. A quality PV company will assess existing rooftop equipment and roof drainage routes and will design the system to make sure it does not influence drainage, and access is available to all systems on the roof for proper maintenance.
- Will a rooftop PV system increase the possibility of damage to the roof from wind/snow loads?
No. The solar companies should design PV systems to meet local building codes for wind and/or snow loads. For this purpose, PV installers carry out a roof assessment to evaluate the roof’s structural integrity before installation. The requirements for determining structural loads on buildings and other structures are given in the standard ASCE 7 – Minimum Design Loads for Buildings and other Structures, which has been adopted into the building codes. Moreover, the designs must be signed and approved by a licensed engineer before installation and must also receive approval from the local building inspection authority.
- How will rooftop PV impede fire fighters’ ability to extinguish a fire or increase the risk of fire?
Reputable PV companies must design PV systems in accordance with new requirements in the 2015 International Fire Code (IFC 605.11) that require clear space at the edges and peaks of roofs for firefighter access. Most of PV installers will also share the PV system designs with the local fire department to approves the design.
- Who is responsible for the warranty, and code compliance of my roof?
The solar company will be in charge for designing and installing the PV system according to relevant building codes. Normally, a reputable solar installer will contact the original roof manufacturer to ensure that the PV system installation does not void the roof manufacturer’s maintenance and warranty requirements. Also, after the PV system is installed, the roof manufacturer will inspect the system to confirm that the system meets the approved design and that the roof warranty remains intact. If any damage done to the roof during installation, it will be covered by the solar installer’s warranty. Dependable solar installers provide suitable workmanship warranty prior to installing a rooftop solar system.
- What happens if I need to replace my roof?
The solar installer will perform a roof assessment and find out if the roof will need to be replaced during the life of the PV system. Typically, if the roof will need to be replaced, building owners are encouraged to replace it prior to installing the PV system to benefit from the Federal Solar Tax Credit for Roof Replacement. However, PV companies include the temporary removal of the PV system for roof replacement after PV installation in their agreement.
1. Successful Rooftop Photovoltaics: How to Achieve A High Quality, Well Maintained, Compatible Rooftop PV System: https://usa.sika.com/content/dam/dms/us01/d/successful-rooftop-photovoltaics.pdf
2. N A B C E P PV Installation Professional Resource Guide: http://www.nabcep.org/wp-content/uploads/2016/10/NABCEP-PV-Resource-Guide-10-4-16-W.pdf
3. Frequently Asked Questions (FAQ): COMMERCIAL ROOFTOP SOLAR: https://betterbuildingssolutioncenter.energy.gov/sites/default/files/attachments/BBA_Commercial_PV_Roofing_Guide_071715_508.pdf
4. Understanding the Cal Fire Solar Photovoltaic Installation Guideline: https://www.fsec.ucf.edu/en/education/southeast_training_network/Background%20on%20CA%20PV%20Installation%20Guide.pdf