America’s Solar Rapid Expansion Program Will Create Design Challenges
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 White House recently released its goal of tripling the amount of solar by 2024, which included provisions for creating a legislative 24-month bridge channel to import components from Cambodia, Malaysia, Thailand, and Vietnam until domestic production is in place. This will significantly amplify the number of designs, components, and installation needs in the market. These new solar panel manufactures may need to work around existing patents that might create different panel dimensions, mounting, and energy collection devices. In any roofing assembly, the introduction of an accessory being installed can become a potential source of leaks or obstructions if not properly designed. Some areas of concern the Tile Roofing Industry Alliance has identified in the past, as products entered for steep-slope markets, have included the following.
The International Building and Residential Codes will likely be the source of the new model codes to address any revisions on performance. Having a formal product approval on new products can help assure that proper installations can be compliant, and any restrictions or limitations identified.
Each solar panel manufacturer will need to provide their installation guide for how to attach their panels properly. For concrete and clay roofing tiles, we do not allow the direct attachment to the tiles. We require the attachment to the sheathing or truss for proper support. The attachment will need to comply with the recognized codes for any wind, seismic, snow, or other live loads to which the panels and roof will be subjected. When attachments are installed, they need to be certain they are not preventing the roof cladding from fully performing as designed.
Based upon the method of attachment, you will need to consider how the roof assembly will be properly sealed. There are numerous bracket, slides, rail, and lag bolt options in the market today. When fastening to the roof sheathing, we consider these as roof penetrations and require additional sealing. The use of code-approved caulk, specifically permitted by the manufacturer of the mounting systems, flashings, or other methods of code-approved sealing should be considered. When larger lag bolts are used, the differential of expansion rates of the fastener versus the sheathing can create a potential leak point if water were to breach the outer cladding. Sealing of the holes through the cladding should also be addressed. For our concrete and clay roofing tiles we require both a deck and top flashing.
With thinner panel designs comes the aesthetic desire to lower the visibility on the roof. When designing a change in height of the current roof cladding, care must be taken to address properly the anticipated water flows. The designs will need to include transitional flashing for both up and down slope to help the water either to transition back downslope to the roof cladding or daylight off the roof at the eave. For the sides, you will need to address the height differential that might include creating a wall abutment that allows easy flashing comparable to a rake end allowing each roof area to be perform independently.
Each solar system will have its unique wiring and collector systems. Your design should consider conduit size, locations, penetrations, and future foot traffic areas for maintenance. Too often, we have seen oversized conduits that raise our tiles preventing them from performing as designed. Cutting of roof claddings for the collection boxes and not properly sealing is another area of concern. When doing as a retrofit solar install, improper installation can potentially cancel any warranties of the roof by the original roof professional. Design professionals might consider integrating a roofing professional into the solar installation process if one is not part of the solar company team. With the push to retrofit solar on existing buildings, it might save potential leaks and identify any other roof related issues prior to starting.