Construction Residential

How to combine a green roof with solar PV

Despite the relatively small roof area, the developer was able to combine both green roof and solar PV array to achieve BREEAM Outstanding.

Despite the relatively small roof area, the developer was able to combine both  green roof and solar PV array to achieve BREEAM Outstanding.

Clapham Park is a residential development spread over 36 hectares in the London Borough of Lambeth. The regeneration programme involved replacing old housing stock with new affordable homes, including a five-storey building of 21 dwellings with a 500sqm biodiverse green roof and solar PV array to meet planning requirements for a BREEAM-rated building.

Despite the relatively small roof area, the developer was able to combine both  green roof and solar PV array by using Bauder green roof solutions. This resulted in a BREEAM Outstanding rating and ultimately a reduction in resident energy bills.

Green roof

The green roof, which includes 35 plant species recognised by the RHS as ‘Perfect for Pollinators’, covers the whole roof area and offers a wide variety of vegetation. The building reduces its carbon impact with the highly efficient PIR insulation and generates approximately 10% of the flats usage with a maximum possible output of 75kWp from the 70 PV modules.

The roof needed to be complete during mid-winter in order to meet the overall construction schedule, which meant the green roof could not be established until the spring of 2017. Bauder’s mix of seed, tackifier and mycorrhizal fungus was therefore used to maximise germination with little watering.

This enabled fast establishment between seeding in April and June, with many British native wildflowers giving a valuable source of nectar to pollinators by August.

Mounting the solar PV

To install the solar PV without damaging the green roof, Bauder’s BioSOLAR was used. This system has been designed  so that the substrate and vegetation provide the ballasted installation mechanism for mounting solar PV arrays. This removed the need to penetrate the waterproofing to secure the PV installation.

The front edge of the PV panel is set at around 300mm above the level of the substrate, which allows liberal growing room for the extensive vegetation without blocking light.