Mounting Solar Panels to Roof Rails

Roof Rail systems are a proven method of securely mounting solar panels. Whether the roof is a home, RV, boat, car, or some other structure, rails are the way to go.

But what is required for a successful rail-mounted solar array?

  • Stability
  • Rigidity
  • Precision
  • Durability

When planning any solar array mounting system, these elements must be taken into account. Failure to provide these features can lead to damage to the panels or failure of the entire array. These are important elements you must address.

I

A Stable Base

A solar rack system is only as good as the foundation it is built on. Roofs of homes, RVs, boats, and cars are very different. They also experience very different environments.

There are several considerations when assessing the stability of the roof your array will rest on.

House or Garage Roof

The roof of a house is the most common location for the domestic solar array. The roofing material and roof substrate are the first items to consider. These elements will help determine where and how the rack system should be mounted.

Roof Structure

It is preferred that the feet of the rack system be mounted and bolted to the load-bearing structure of the roof.

The best practice is mounting to roof rafters or trusses. If it is not possible to use the preferred method, there are always alternatives.

Preferred methods:

  • Rafter.
  • Truss member.
  • Beam.
  • Other roof structural component.

Alternative Methods:

  • Added support structure.
  • Specialize fasteners.
  • Additional mounting hardware.

Other Domestic Structures and Ground Mount Arrays

Any structurally sound domestic building can support a solar rack system. A shed, pool house, or an open structure like a carport, would make an excellent support for an array.

The same structural considerations as a house or garage would have to be taken into account.

Multi-use Ground Mounted Arrays

  • Picnic Cover.
  • Open porch.
  • Covered car park.

Boat, RV, and Car Roofs

Mounting small solar arrays on vehicles is a great application of technology. The roof of a vehicle is a structurally sound location that can support a small array.

Rack systems for RVs and boats are available. Bike and luggage racks on cars and pickup trucks can easily support a small panel or two.

The key to rack mounting a panel on your vehicle is knowing the manufacturer’s recommended procedure and sticking to it.

Limitations In Vehicle Roof Rack Mounted Arrays:

  • Limited array space.
  • Limited mounting locations.
  • Takes up space from other functions.

Boat and RV Roof structures

The roof of a boat or RV is a delicate structure. They are designed to protect the occupants from the weather while being lightweight.

Rack systems for mounting solar to these roofs do exist. Some RV and Boat manufacturers have included mounting points for solar.

If you are unsure, contact the sales rep or manufacturer of your RV or boat to inquire about rooftop solar mounting accommodations.

RV and Boat DOs

  • Learn about your roof.
  • Plan on a small array.
  • Find an appropriate rack system.

RV and Boat DO NOTs

  • Drill holes in your roof.
  • Use house roof mounting hardware.
  • Cover existing equipment with solar panels.

Rigidity of Solar Roof Mount Racks

Solar array rack systems are intended to remain flat and stable. Roof rail mounting systems achieve their rigidity by using extruded aluminum rails that will not flex under normal use.

While products designed specifically to mount panels are the norm, other types of rails and hardware can provide satisfactory support.

  • Solar specific rigid mounting systems.
  • Auto roof racks as solar mounts.
  • RV roof mounting systems.
  • Boat roof mounting systems.
  • DIY Roof mount systems.

Manufactured house roof rack systems.

The main benefit of manufactured rack systems is their ease of use. Such systems offer a variety of feet to accommodate many roofing materials.

Panel mounting is simplified with captured studs, nuts, even push and click fasteners. These systems enable the homeowner to position arrays on nearly a flat surface and the hardware is adaptable to any roof profile.

PROS

  • Components designed for easy assembly long life.
  • Rails can be trimmed to accommodate any roof profile.
  • Various mounting feet available.
  • Can accommodate any panel size.
  • Neat, professional appearance.
  • Provides rigid mounting for panels.

CONS

  • Rack systems can be expensive.
  • Can only be used on flat or nearly flat roofs.
  • Not easily adaptable to other applications.

RV and Boat roof rack mounting systems

Recreational vehicles have made use of solar power for years. There are racks systems available that are appropriate for both RVs and boats.

Due to the nature of building materials used in these vehicles, rack feet use adhesives rather than fasteners to attach the components to the roof.

RV roof rack systems

Roofs on RVs are flat or slightly arched fiberglass structures. While they can bear considerable weight and are rigid enough to support a panel, they should not be punctured.

A rigid RV solar array must be mounted on a manufacturer-approved luggage rack or using adhesive feet.

Some RV roofs can not accommodate a luggage rack. In such a case, an adhesive feet system must be used.

Appropriate methods to rail mount panels on RVs:

  • Manufactured luggage rack with cross members.
  • Individual panel collapsible rack.
  • Adhesive rack feet.
  • Adhesive backed semi-flexible panels mounted to roof,

Boat roof rack systems

Boats have limited space and fragile roof material. While the roofs are structurally strong, the fiberglass used is not designed to have fasteners put through it.

The common practice in boats is to mount panels on secondary structures designed for the purpose.

There are many solar rack mounts on the market. Surface-mounted panels tend to be semi-flexible, adhesive-mounted panels.

Appropriate practices in mounting panels on a boat

  • Task specific rigid panel mounting structures.
  • Adhesive mounted feet for rigid rail system.
  • Semi-flexible adhesive backed panels on roof or deck surfaces.

Car Roof Racks

If you are a camper or run a small business out of your car, a panel on the roof of your vehicle may be a good source of power. A factory roof rack or after-market solar rack is rigid enough to mount a panel or two.

There are a few issues that must be taken into account when mounting to a roof rack:

  • Span between factory rails.
  • Curve of rails.
  • Turbulence and vibration created by wind.
  • Fasteners.

Factory rack systems

If your car is equipped with factory luggage rack rails, the distance between rails is nearly four feet. A large panel could cover this distance.

The issue is that when the vehicle is in motion, vibration and flex incurred by wind turbulence may become severe.

Two or three narrower panels oriented with a long dimension parallel to the rack can alleviate this issue.

Issues with factory luggage rack array:

  • Requires cross members.
  • Several small panels rather that one large panel.
  • Must find hardware to mount panels to cross members.
  • Anti-vibration fasteners.
  • Will require some experimentation and refinement.
  • May get costly and/or result in damaged equipment.

After market vehicle roof racks

There are after-market rack systems that are conducive to mounting panels. Most of these are intended for off-road or camping applications.

These racks are flat and strong, but not designed specifically for solar applications.

There are several Blogs and U-Tube videos with individuals who have successfully mounted panels on such racks. Such applications would still require some experimentation and creativity.

Issues with after market rack arrays:

  • Aftermarket racks can be quite expensive.
  • Must find hardware to mount panels to racks.
  • Anti-vibration fasteners.
  • Will require some experimentation and refinement.
  • May get costly and/or result in damaged equipment.

While car-based solar is a popular topic, it is apparent that it is not as easy as one would suspect. The fact that there are very few (or none) car roof solar systems on the market suggests it is not easy to accomplish.

A viable option is flexible panels. There are many flexible panels on the market. Some come with adhesive backs that will semi-permanently affix them to a vehicle roof.

Other factors when setting up a roof top solar rack system

The precision and reliability of hardware and components must not be short-changed when designing a roof rack system.

Manufactured rack systems are typically built of high-quality aluminum and stainless steel.

These materials are stable and resistant to most atmospheric contaminants. When putting together a rack system, do not skimp on the hardware.

Hardware to use:

  • Stainless steel.
  • High Quality Aluminum.
  • Well machined nuts and bolts.
  • Hardware designed to work with the rails.
  • Chromed or galvanized components.

Hardware to avoid:

  • Bare common steel fasteners.
  • Loose fitting nuts and bolts.
  • Generic hardware that does not properly fit rails.

Review and References

Roof Rack solar mount systems are the most common form of supporting a domestic solar array. On ground-based structures roof, mounting systems are plentiful.

On RVs and Boats, solar roof mounting is fairly common. On cars, roof-mounted solar is not impossible, but not readily available.

Sources

Solar Panel Setup FAQ

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