November 14 2013 0Comment

Mounting Solar PV Panels on a Metal Roof

A recent project required the installation of rigid solar panels rack mounted on a metal roofed building.

mountingsolarpvpanelsonmetalroofThe prime consideration for any rack mounted solar system is maintaining the waterproof integrity of the roofing system. Piercing the metal roof, then waterproofing those penetrations is always an issue.

For this particular project, the owner understood the benefits of investing in a polyurethane foam roofing system over the existing metal roof:

  1. The first is the insulation provided by the foam which will contribute to an even lower energy bill by reducing the Air Conditioning cost.
  2. Foam roofing over metal also acts to deaden noise
  3. Waterproof the fasteners
  4. Rigidize the metal roof (prior to applying the foam, you could not walk on the roof without damaging it)
  5. The foam also acts as a sealant for any penetration made through the metal skin

The first step in the application of solar panels on a roof top is to create a layout of the selected panels on the roof to meet the requirements of orientation and to be shade-free. The next step is to ensure the layout meets with the approval of the local Fire Marshall – and these vary from city to city. Most of these issues are concerned with set-backs from all sides of the roof and the ridge. Once all of these criteria have been met – one can calculate how many solar panels can be placed on the roof and how much power can be created with the selected solar panels.

In this particular instance we were able to achieve a potential 22.08kW DC from 96 panels.

Once the layout was completed the installation of the racking supports could begin. These were secured by screwing the support stand-off “legs” into the supporting metal structure of the roof system. The legs, consisting of a circular tube mounted to a flat plate, were fastened through the metal roof skin into the structural supports using tec screws.

mountingsolarpvpanelsonmetalroof2Once these were positioned and secured, the foam roofing was applied to a depth of 1 ½” over the entire roof area. An additional boot was placed over the legs to ensure the connection to the metal structure was watertight.