• TMC Engineering Ltd.

Solar Roofs

Metal Roofing + Solar Arrays: The Perfect Combination

Metal Roofing
  • Low maintenance during its more than 40 year lifespan.
  • Durability for wind, fire, hail and U.V.
  • Virtually 100% recyclable, allowing for reduced landfill mass and comprised of 25% to 35% post-consumer recycled steel.
  • Cool roof colors of metal panel systems.
  • Unsurpassed warranties compared to both conventional roofing companies and solar module manufacturers.

Solar

  • An ecological resource with a low carbon footprint that harnesses the sun’s renewable energy.
  • A sustainable resource that will produce 85% of rated energy production 20 years after installation.
  • A diverse resource, available in a variety of technologies including modules of polycrystalline and thin film.
  • A reliable resource, producing energy anywhere the sun shines at a fixed and known cost that is not subject to the fluctuation of fuel costs and utility rate escalations.

The Perfect Blend

The combination of metal roofing systems with PV systems provides a number of benefits for the building owner. Below is a breakdown of the support to these benefits:

  • The PV system’s efficiency typically improves when it’s installed on a cool metal roof increasing the energy output of the solar modules.
  • The solar modules can be installed on a metal roof system with no penetrations into the roof, allowing the metal roofing warranty to remain intact.
  • Nearly 80% of PV installations occur on existing construction. The service life of a metal roof system is compatible with that of a solar array.
  • PV systems typically last 20-25 years. Why install a system on a roof that will only last 15-20 years? Instead, choose a Star metal roof that will last 40 years or more, allowing you to remove the existing solar array to install a new one on the same roof.

The Solutions

Glass-Based
Crystalline Silicon:

The crystalline solution is a rigid module which can be installed on standing seam roofs using a non-penetrating clamp assembly. This option provides the highest energy conversion efficiency at 13-18%, which is about 10 watts per square foot. The glass-based crystalline module weighs 3-4 pounds per square foot. The modules perform best during peak sunlight hours.

Flexible Thin Film:
This lightweight option, approximately ¾ pound per square foot, is typically adhered to the metal roof panel in a Star manufacturing facility, allowing the solar array to be installed as the roofing system is installed. Thin film is less efficient than crystalline modules with a 5-10% efficiency rate at about 5 watts per square foot. Flexible thin film does perform better than crystalline modules in low light conditions.

Pre-designed Grid-tied Kits

From 700W to 60kW, Star kits work well for existing or new commercial construction projects. Star will provide the education, guidance, technical support and most of the materials needed for a successful solar implementation.

Each Star solar kit contains the following:

  • Leading brand name polycrystalline or amorphous silicon PV modules.
  • Inverter
  • AC and DC disconnect switches
  • DC Electrical wiring (DC fuses and 50’ wire whips for each string sized to meet the requirements of the National Electric Code (NEC) to connect the solar module strings to the combiner boxes).
  • Combiner boxes
  • Lightning arrestors
  • Warning labels required by the NEC
  • Mounting hardware for PV modules
  • One-line electrical drawings
  • Electrical specifications for the contractor’s installation
  • All required specifications for architectural applications
  • Module and inverter installation manuals


An electrical contractor, knowledgeable about solar PV installations, will be required to install the electrical components of the PV system. The contractor will also decide the best location for the inverter and provide wiring and conduit to run from the combiner boxes on the roof to the inverter and from the inverter to the meter box as well as all disconnects and any other equipment required by the local utility company. The electrical contractor will contact the local utility company to determine all requirements for the PV system to be connected to the grid.

Before installing a solar array on any roof, a registered professional engineer should be consulted to determine if the roof is capable of accepting the additional loads.

To aid in determining which type and size solar array is best for a particular project, the following information is offered:

  • The best direction for the solar array to face is south, though roof areas facing east or west can also be used.
  • Usually about 75% of a roof area can be utilized for the solar array, unless there are obstacles on the roof such as skylights or rooftop equipment. Shading of the solar array should also be investigated.
  • Solar modules cannot be installed to the roof edge. Adequate distance must be left at the roof edges for roof access.

Typical Commercial Roof Installation Example PV System

  • 15kW with polycrystalline modules
  • Metal Roof
  • South-facing
  • ½”:12″ slope
TMC & Star have the expertise to model PV systems in this fashion for most locations in the Bahamas & throughout the Caribbean as well as perform payback calculations for those systems taking advantage of the latest incentive programs.