.png)
TYPES OF BIOSOLAR SYSTEM
Biosolar roofs are delivered using mounting systems designed to work in harmony with a green roof build-up. While individual manufacturers offer variations, most systems fall into two main categories: integrated systems and overlay systems. Understanding how each approach behaves helps designers select the most appropriate option for performance, planning, and installation requirements.
INTERGREATED BIOSOLAR SYSTEMS
Integrated biosolar systems are designed as a single roof solution, where PV, planting, drainage, and structure are coordinated from the outset.
Integrated biosolar systems are designed to sit within the green roof build-up from the outset.
The PV mounting structure interfaces directly with the drainage or retention layers, while vegetation contributes to stabilisation, cooling, and ecological performance.
Rather than treating solar and planting as separate elements, the system is engineered as a single, coordinated ecology–energy solution that balances performance, access, and long-term durability.
.png)
Pros
-
Greater ecological integration: vegetation grows up to and around the frames
-
Cleaner, lower-profile appearance
-
Reduced need for additional ballast when designed correctly
-
Strong alignment with biodiversity and planning objectives
-
Good airflow beneath modules supports panel performance
-
Typically better shading transitions and microhabitat creation
Cons
-
Must be coordinated early in design (structural loading, drainage, sequencing)
-
Installation tends to be more specialist
-
Less flexible for retrofits where the green roof already exists
-
System choice may constrain vegetation type or depths
OVERLAY BIOSOLAR SYSTEM
Overlay systems place PV mounting above a green roof, but the PV and planting are still largely separate systems.
An overlay biosolar system uses PV mounting frames installed above an existing or newly installed green roof. The green roof functions as a continuous vegetated layer, while the PV system remains structurally separate.
This approach allows solar and green roof systems to be delivered independently, offering flexibility in sequencing, procurement, and future alterations. However, because the systems are not fully integrated, ecological interaction and long-term optimisation depend heavily on careful layout and height design.
Pros
-
Highly flexible and easy to retrofit
-
PV and green roof systems can be installed or replaced independently
-
Familiar for installers experienced with conventional ballast PV frames
-
Suitable where green roof and PV procurement routes are separate
Cons
-
Less ecological interaction compared with integrated systems
-
Often requires additional ballast (depending on wind calculations)
-
Vegetation may be partially shaded out if system height is not optimised
-
Greater risk of creating inaccessible voids beneath frames
SYSTEM SELECTION CONSIDERATIONS
🎯 Project goals – biodiversity uplift, UGF/BNG compliance, energy yield, and overall performance targets
🏗️ Roof structure & loading – available load capacity and how the system build-up affects structural design
🌱 Vegetation type & depth – planting strategy, substrate depth, and compatibility with the PV mounting approach
🧰 Access & maintenance – long-term access routes for vegetation care, inspections, and PV servicing
🧑🔧 Installation & sequencing – contractor skillset, build sequence, and coordination between trades
👁️ Aesthetics & planning – visual impact, roof appearance, and feedback from planners or stakeholders
Both system types can deliver strong environmental value when designed correctly. The key is ensuring compatibility between the green roof layers, drainage strategy, mounting structure, and PV layout from the earliest design stages.
WHERE TO GO NEXT
To explore how system choices influence project performance and coordination, continue to Key Design Considerations.
For planning alignment and policy drivers, visit Biosolar and Planning / Policy Context.
If you’re preparing early-stage layouts or assessing feasibility, the Pre-Design Checklist is available in the Downloads section.
If you’re seeking a specialist contractor to deliver a biosolar roof system visit PV Plus
