Solar Roofing: Best Practices
By Conor Trujillo, Assistant Director of System Design.
As the use of rooftop solar as an energy resource increases across North America, it is important for both installers and building owners to understand industry best practices. Paying attention to a few key elements before and during a solar installation will ensure your project provides the optimal performance for the lifetime of the system.
Know Your Roof
The first consideration for rooftop solar should always be the condition of and warranty on the roof. Depending on several factors, the useful life of a roof can range from 10 - 30 years. Checking the manufacturer’s warranty to ensure the roof will not need to be replaced during the lifetime of the solar system can help installers avoid costly “repair and replace” expenses down the road. At the beginning stages of the project, installers should also check for any signs of rotting, mold, or water damage that may compromise structural integrity.
Before designing a rooftop solar system, you must understand the roof's orientation, pitch, and surface type. For pitched roofs, the orientation and slope are predetermined, so it is simply a matter of installing at the optimal position on the roof. For flat or low sloped roofs, the system will require extra racking components, such as standoffs or tilt legs, in order to position the panels to optimize performance. The roof surface material makes a difference in the type of mechanical connection needed. Different mounting equipment is required to install solar on sheet metal, spanish tile, asphalt, or standing seam roofs, so it’s important to identify the right type of attachment method as early as possible in order to limit delays during on-site installation.
Depending on the project’s location, it is also critical to factor externally applied loads like wind and snow into your analysis to prevent compromising the building’s structural integrity. For design guidelines, the American Society of Civil Engineers (ASCE) has good resources on the minimum loads of buildings and other structures.
Understand the Relevant Codes
A variety of building and electrical codes will dictate do’s and don’ts for installers, including the International Building Code (IBC) for waterproofing and mounting guidelines, the National Electrical Code (NEC) for electrical interconnection requirements, and the National Fire Protection Association (NFPA) for fire safety requirements.
At the end of the day, local rules will reign supreme. Installers must know and comply with all local permitting rules which can vary greatly between jurisdictions. For customers, it’s best to always use a NABCEP certified PV installer who understands the local codes. If possible, ask for references and use an installer with at least 3-5 years of experience.
Use Proper Flashing Techniques
After selecting the appropriate mounting components, the first objective is to minimize the number of roof penetrations by only making connections where necessary. Installers should approach the roof with a plan for where and how many mounts will be required to securely hold the array. As the majority of construction litigation stems from water intrusion, proper waterproofing can mean the difference between a functional solar system and one which may leak and cause damage over time.
The IBC (Section 1503.2) requires that ”Flashing shall be installed in such a manner so as to prevent moisture entering penetrations through the roof plane.” To avoid water from entering the roof during the lifetime of the system, installers should use flashing around every penetration point, and seal with multiple layers of waterproofing. This double sealing technique requires flashing both the underlayment of the roof, as well as using a raised sealant on the surface, to maximize the amount of water deflected from the penetration point.
Make Safety A Priority
During a PV installation, safety should be of the utmost concern. Falls are a leading cause of injury and death at construction sites, and are easily prevented by using a personal fall arrest system (PFAS) or with other fall protection strategies, such as safety nets or guardrails. Due to the nature of the equipment used, there is also a risk of severe electrical shock, which can be avoided by wearing proper Personal Protection Equipment (PPE) such as footwear, insulated hard hats, and rubber insulated gloves.
Improper installation can be costly, and may reduce value to customers and returns to developers. When installers take the time to ensure proper system design and compliance with building and electrical codes, solar can provide reliable, clean energy to customers for years with minimal maintenance. Utilizing best practices in throughout the project design and installation offers the best form of insurance over the long term.