Metal roofs are known for their durability, sustainability and versatility, and are increasing in popularity in the solar marketplace.
Metal roofing is a natural choice for mounting solar PV as it provides an ideal platform and features the only service life that exceeds the service life of a solar PV system.
Service Life
In the commercial/industrial market sector, the field/lab study published by the Metal Construction Association indicates that the service life of (standing seam) coated steel is in the range of 70 years.
Many alternative roofing systems will expire long before the life of the PV system. This leads to costly disassembly of the PV array, re-roofing and re-assembly.
The service life of solar PV is between 28 and 37 years with an average of 32.5 years, according to a Berkeley study.
Aside from metal, there are no other roof types that measure up to that without requiring replacement.
Metal roofing is also the most sustainable roofing type (at an 85% recycling rate) and is conducive to lower solar installation costs.
Ease of Installation
It is easier and less expensive to mount solar to a metal roof than any other roof type.
Solar PV can be mounted on the roof’s ribs or standing seams, which serve as the rails for reliable mechanical attachment of modules.
Metal roof solar mounting can offer fewer components, light-weight materials, better load distribution and provide a zero-penetration system for standing seam metal roofs while preserving roof warranties.
Lifetime ROI
Once the decision is made to install solar, often a new roof is called for.
More and more building owners are replacing their roofs with metal roofs because not only is the metal/solar asset less expensive upfront than other solar roof combos, but it also leads to improvements in the lifetime ROI of the system.
The costs of the PV array and roof should always be regarded as a single asset.
When computing PV service life and ROI, don’t forget the cost of roof replacement! =
The solar array must be totally dismantled and then re-installed during the process.
Often, even the initial cost of solar and a metal roof is less expensive. Factor in roof replacement and the advantages become grossly magnified.
Completing a PV system re-roof for a traditional (non-metal) roof would include several exorbitant costs:
- Remove modules;
- Remove mounting and racking system;
- De-commission PV system;
- Re-roof;
- Re-install PV system;
- Re-commission PV system;
- Possibility of damaged components;
- Potential for new wiring necessary;
- System downtime
With metal, you can avoid roof replacement due to its long service life. The roof will still be going strong long after the service life of the solar array has expired.
Main Take-Away
Solar contractors should know about roofing alternatives and service lives to bring added value to their customers.
The long-term costs of both the roof and solar PV should be evaluated as a single system.
Advising the mounting of a solar array with a 30-year plus life on a TPO or asphalt shingle roof with a 15-year life is a bit like mounting a Ferrari engine on a Mini-Cooper chassis.
Who would do that?
