Proper Roof Designs When Going Solar
by Richard K. Olson, president & technical director, Tile Roofing Industry Alliance
(Editor’s Note: Richard K. Olson is president and technical director for the Tile Roofing Industry Alliance. The association represents industry professionals involved in the manufacturing and installation of concrete and clay tile roofs in the United States and Canada, and works with national, state, and local building officials to develop installation techniques, codes, and standards for better roofing systems. Olson can be reached at firstname.lastname@example.org.)
The energy conservation movement continues to expand to a greater audience in the design and code community. As part of that growth, the inclusion of solar alternatives is being used in most new construction designs. Even the retrofit markets are showing increased demand. The roofing industry is challenged to stay abreast of all the options, equipment, and restrictions these solar systems require. Design professionals will need to provide greater details for the proper installation requirements. In most cases, the solar systems are installed by professionals that are not necessarily roofing contractors or have limited exposure to the complexity of the roof systems they are about to integrate with. For steep-slope applications, this can create issues with water intrusion, deadloads, and long-term roof performance if not properly addressed. There are several areas to be considered by the design community when it comes to solar installations.
While roof orientation for maximum sun exposure is ideal for energy generation, it is not always the best location for the roof system. The design should consider the full roof assembly it will integrate with. Proximity to roof penetrations, venting, lighting, equipment, or utilities will need to be reviewed. For steep-slope roofs, these are areas where special flashings, underlayments, venting, and accessory products may be in play. Compromising the existing roof system may create leaks, performance issues, or reduce service life to the roof assembly under the solar systems. Design professionals can help balance the ideal energy versus roof assembly needs.
All solar systems require wiring to transmit the energy to a collector or transformer. The proper sizing and routing of conduits are often product or system based. They will need proper interface with the roofing assembly to ensure that the roof will perform as designed. In steep-slope roofing, that will require proper understanding of the roof assembly from the sheathing to the cladding. We have seen too many installations where the placement of the conduit has raised the roof cladding, allowing water to breach the system or create point load issues that can lead to early failure of the assembly. In other cases, the installation of the conduit over the roof cladding has create penetrations with fastening, or re-direct of upslope water via lateral movements that can create issues with current flashing already in place.
It is important to understand what flashing will be required to allow for proper performance. In the case of roof tiles, both a top and base flashing are required when the solar systems create penetrations of the assembly. Support systems, racks, rails or other fastening systems are not allowed to be mounted directly to tiles. Instead, they are required to be attached to the sheathing, truss, or other properly design points that can handle the weight, uplift resistance, and support needs of the solar systems. Each of the solar manufacturers will have to provide detailed installation instructions for how to mount, fasten, and flash to meet the codes and roof assembly requirements. How they meet a top flashing and base flashing will vary. When sealants, caulkings, or other flashing materials are utilized, they will need to be called out and should use code approved products.
While new construction provides a greater opportunity to schedule installation of such systems in a more organized sequence, the retro-fit markets can be challenging. For new construction, the solar installer should be working in collaboration with the roofing professional for integration of the mounts, wiring, and accessory components to meet the needs of roof and solar performance. In retrofit, this is often controlled by just the solar manufacturer. When systems are not properly installed, the eventual leaks or performance issues are unfairly reverted to the original roofing contractor. Inspection of such installations are often performed by electrical inspectors that may not be knowledgeable of roof assembly requirements.
Once installed, the building owner should be properly educated on the long-term maintenance needs. Depending upon the type of system, there may be opportunities for accumulation of debris, vegetation, or dirt that can create fire, water, or ventilation issues for proper roof performance. Additional foot traffic areas should be identified where future solar system work may need to be performed. Design professionals can enhance these areas with greater support, flashings, or traffic accessories.
While solar performance can increase the efficiencies of homes, the location and size of such panels can create reduced performance in other areas. For instance, the thermal mass and above sheathing ventilation of concrete and clay roof tiles can be reduced when the solar collectors of large size are placed above tiles. This would be true for other lighter colored roofing claddings that are available in the market when the roof areas are covered with panels.
The time spent researching the full requirements and proper system design can help mitigate most of the issues in the field today. With new products entering the market, we all need to understand and work in a collaborative effort to improve the long-term performance of the roof system.