Block ip Trap

Rail-less Solar PV System Mounting for Metal Roofs

15 Nov 2021

By Rob Haddock

S-5! Article Image 1With increasing popularity, the metal roof is the ideal host for mounting solar photovoltaics (PV).  It is the only roof type with a service life (in the range of 50-70 years) that actually exceeds the service life of a solar PV system (an average of 32.5 years). Most alternative roofing types will expire long before the life of the PV system, leading to costly disassembly of the PV array, re-roofing, and re-assembly. And at an 85 percent recycle rate, steel is one of the most recycled construction materials available.

Mounting Solar PV on Metal Roofing

When it comes to attaching solar modules to metal rooftops, using conventional rails has been the traditional method. Yet, familiar concepts don't necessarily deliver the best outcomes; the advantages of rail-less, direct-attach solar module mounting solutions are moving the industry in a new direction.

When interest in mounting solar PV on rooftops first began, the practice of using continuous aluminum rails to mount PV modules was a practical application for all roof types. Eventually, innovation opened new doors and solutions were developed specifically for metal roofing, completely bypassing the need for rails. 

Reduces Costs

Rail-less solutions leverage a roof's existing construction. The uniqueness of metal roofing is that the seams of the standing seam metal roof, or the trapezoidal or corrugated ribs on an exposed-fastened roof can be used as inherent (and cost-free) "rails" for mounting PV via tested and engineered mechanical attachments. This eliminates the need for a traditional rail system.

The material (weight) required for a direct-attach mounting system is  ±3 lbs/kW vs  ±19 lbs/kW for railed - a savings of 85 percent - and lower collateral loads to the structure. Expect cost savings on hard goods of up to 45 percent. Direct attachment to a metal roof is also accomplished with 65-75 percent fewer components. Because every clamping point on a PV module attaches directly to the roof, rail-less mounting results in 25 percent better load distribution to the roof, and can preserve both its integrity and warranty.

Simplifies Logistics

Rail-less reduces the overall costs of logistics; shipping long lengths of rail to project sites, storing them, and transporting them up to a rooftop is a costly and often logistical nightmare. Rail-less attachments are 15 percent the weight and 10 percent the volume of railed systems. For example, rail components for a 750 kW job require several semi-trucks to transport. The same rail-less solution fits in a short-bed pickup truck. This savings in shipping costs alone - up to 70 percent - is driving mounting system decisions to rail-less.  Fewer logistical hassles transporting the product to distribution, then to the site, and then staging on-site and onto the roof makes rail-less an increasingly popular choice. Nolarge storage area is ever needed and the need for lifting equipment is reduced or eliminated.  

S-5! Article Image 2

Eases Installation

Rail-less solutions have transformed the installation process. Installers can easily mount around obstacles without the awkward field-cutting of rails. Plus, impromptu changes in the module layout when needed are seamless. 

With fewer components than traditional systems, rail-less solutions make it simple and easy to get all the components up on the roof and into place, which is especially beneficial when working on a steep slope. On a job of 12kW, all mounting goods can go to the site and up the ladder in a bucket or tote bag, along with all tools needed for the install (just a gun and one or two driver tips). State-of-the-art rail-less solutions also provide slots and other features for wire management to help organize this critical part of a PV system.

Labor Savings

The key to labor savings (30 to 50 percent) is twofold: the elimination of time traditionally needed to measure, locate and install rails, and the simplicity of rail-less attachment- requiring far fewer components to manage and install. Rail-less is designed so roof clamps or brackets can be quickly aligned and modules installed "on-the-fly" using successive modules to locate and install attachments with no need to measure or snap lines. Installers have reported installation of more than 20 modules per man-hour, all in-on 50kW-up jobs.

Protects the Investment

The value of metal roofing lies in its durability and sustainability. Any roofing attachment needs to ensure this durability and long life-cycle remains intact. The low profile offered by a rail-less system provides an aesthetically pleasing appearance with its sleek visual appeal, helps prevent animals and debris collecting under the PV modules, and safeguards the solar array's performance and integrity of the roof. The added benefit is the proper system protects the roof's integrity (and warranty) for the long term.

S-5! Article Image 3Rail-less Benefits:

  • Reduced Material Cost
  • Reduced Freight Cost
  • Reduced Labor Cost
  • Reduced Handling Logistics
  • Reduced Dead Load to Roof
  • Better Distribution of Load
  • Faster on-and-off the Job
  • Strength to Resist Any Wind Speed
  • Natural Critter Guard

Rail-less is moving forward in the field of metal rooftop solar mounting, positioning it to be the new solar mounting standard for the future. It takes time for any industry to adapt to newer practices, but the advantages of rail-less mounting are increasingly well known. Because of the cost savings on materials, labor and freight, ease of installation and flexibility of module layouts, simplified and low-cost logistics and return on investment, rail-less is gaining traction-fast. As more installers and contractors experience the benefits of rail-less mounting firsthand, these innovations are a popular go-to solution for metal roofs.


S-5! CEO and Founder Rob Haddock, is a former contractor, award-winning roof-forensics expert, author, lecturer and building envelope scientist who has worked in various aspects of metal roofing for five decades. He began ground-breaking innovation of penetration-free ancillary attachment solutions in 1991, and holds 60+ U.S. and foreign patents. Together with his son, Dustin, they co-invented a rail-less direct-attach solar solution that provides a simple, secure method to "lay & play" PV modules with tested and engineered attachment to the only roof type that outlasts the solar-the metal roof. 

S-5! |



Author: Rob Haddock
Volume: 2021 November/December