When installing solar panels on a flat or low-slope roof, the mounting method is one of the first things to consider. Two options are commonly used: ballasted solar mounting systems and penetrating roof mounting systems. Neither is the right choice for every project. Roof construction, structural capacity, wind conditions, waterproofing, and installation requirements all need to be considered before making a decision.

A ballasted mounting system holds the solar array in place with ballast, usually concrete blocks or other approved weights, rather than fastening directly through the roof membrane. One of its biggest advantages is that it can avoid or greatly reduce roof penetrations. This can be useful on roofs where maintaining the existing waterproofing system is a priority.

Ballasted systems can also make the installation process relatively straightforward. The mounting components can be arranged around existing roof features, such as drains and access paths, without creating a large number of new attachment points. However, the weight of the ballast cannot be overlooked. The roof structure needs to be checked to make sure it can safely carry the panels, mounting system, and additional ballast.

A penetrating roof mounting system takes a different approach. The mounting structure is mechanically attached to the roof or, where appropriate, directly to structural members below the roofing material. When properly engineered, this type of system can provide a strong connection and effective resistance to wind uplift without adding large amounts of ballast to the roof.

The trade-off is that roof penetrations need careful attention. Each penetration has to be properly sealed and integrated with the existing roofing system. Flashing, waterproofing materials, and installation details all play a role in preventing future leakage. For this reason, the mounting installation should be coordinated with the requirements of the specific roofing system.

Wind conditions are another important factor. A ballasted system relies on its weight, layout, and aerodynamic design to resist movement, while a penetrating system transfers loads through mechanical connections to the building structure. Local wind conditions and the roof's exposure should therefore be included in the mounting design rather than treated as an afterthought.

For some projects, the decision may also come down to the condition and expected service life of the roof. A ballasted solution may be attractive when roof penetrations need to be minimized, while a penetrating system may make more sense when structural attachment is readily available and keeping roof weight low is important.

SIC Solar supplies photovoltaic mounting systems for different flat-roof applications. The appropriate mounting configuration can be selected according to the roof structure, project location, wind and snow conditions, panel layout, and installation requirements.

RFQ Questions for Solar Roof Mounting Systems

Q: Which is more cost-effective, a ballasted or penetrating mounting system?
A: There is no fixed answer. Total cost depends on the roof structure, required ballast, mounting components, labor, project size, and installation conditions. A project-specific quotation gives a more accurate comparison.

Q: Does a ballasted solar mounting system require roof drilling?
A: In most cases, ballasted systems are designed to avoid mechanical penetration through the roof membrane. The exact design depends on the roof and system configuration.

Q: Can a ballasted system be used in areas with strong winds?
A: Yes, provided the system is properly engineered for the local conditions. Ballast weight, panel arrangement, wind deflectors, roof height, and site exposure may all affect the design.

Q: What information is needed for an RFQ?
A: Useful information includes the roof type and dimensions, project location, panel specifications, system capacity, roof load capacity, local wind and snow loads, and preferred mounting method.

Q: Can a penetrating system be installed on a waterproof roof?
A: Yes. However, every roof penetration needs to be properly detailed, flashed, and sealed in accordance with the roofing manufacturer's requirements.

Q: How do I know which mounting system is right for my roof?
A: Start with the roof construction, structural capacity, waterproofing requirements, local environmental loads, and installation conditions. These factors will help determine whether ballast, mechanical attachment, or another mounting approach is more suitable.

Q: Can SIC Solar help select a mounting solution?
A: Yes. The mounting system can be matched to the roof structure, panel specifications, environmental conditions, and project requirements to develop a suitable configuration.