Ballasted mounting system and Sol PV panels

Solar PV on a domestic flat roof?

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Ballasted mounting system and Sol PV panels
Van Der Valk mounting rail and JA Solar panels installed by Tethys Energy Ltd
Van Der Valk Mounting rail installed by Tethys Energy

Earlier this year, Tethys Energy began a Solar PV installation on the flat roof of a domestic property in Hampshire. This on-roof system is weighted down with ballast and installed so that neither the panels, nor the mounting kit penetrate the flat roof’s membrane (which makes it a safer bet for avoiding leaks and damage to the roof).

A flat roof install should have a pitch of less than 5 degrees to be able to support a ballasted system. If the slope is greater than this amount, a penetrative fixing system would be required. This would keep the panels parallel to the roof and would need be fixed into the rafters much like a pitched roof install.

What are the requirements?

The solar mounting system for flat roofs (shown here in the photos), has been developed while taking roof structure and wind load into consideration and so complies with the strictest safety requirements.

The system is installed on rubber feet set at a prescribed distance, so that no metal parts or concrete ballast come into contact with the roof membrane. The mounting rail sits upon the rubber feet and concrete lintels are added at the correct loading points (designed to be distributed with heavier ballast around the edges of the array). The Solar PV panels are then attached to the mounting rail at the correct angle to complete the roof side of the Solar PV system.

This ballasted system is ideal in a commercial setting, where the roof is generally larger, reinforced for load bearing and no planning permission is required.

Generally speaking, all domestic flat roof solar PV installations require planning permission and pitched roof installations are generally covered under ‘permitted development’. (Planning permission is required in a domestic flat roof install, if the panels raise up more than 200mm from the roof edge, as it does for this ballasted system). Commercial roofs do not have this restriction.

The system is compatible with most roof membranes and solar panel brands. A full structural assessment is carried out prior to installation to ensure that the roof is capable of taking the additional weight.

Install Details

The installed system shown in the photos is a combination of JA Solar panels and Van Der Valk mounting system. This mounting system is compatible with a wide range of solar panels. Tethys Energy completed this install with a GivEnergy 8.2kWh storage battery and a GivEnergy 5kW hybrid inverter.

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