Modular and MMC homes are the ideal platform for FHS-compliant solar. In-roof PV cassettes are factory pre-fit onto the roof module under controlled conditions, cutting on-site labour to a 2-hour final connection per plot — and MMC fabric routinely beats the FHS air-permeability target without on-site sealing.
Why MMC and solar fit together
Modern Methods of Construction — panelised timber-frame, volumetric modular, hybrid steel-frame and SIPs — share a defining characteristic: the building is substantially assembled in a factory before it reaches the site. That changes the economics of solar PV in three ways:
- 1Factory pre-fit. In-roof solar cassettes are installed on the roof module at the factory, weatherproofing tested under cover, and craned into place as part of the module. On-site labour drops from ~10 hours (site-built on-roof) to ~2 hours per plot.
- 2Air permeability advantage. Factory-built modules test at 1.5-2.5 m³/(h·m²), beating the FHS 3 target without the deliberate on-site sealing that site-built homes require.
- 3Service integration. MVHR ducting, inverter location and battery provision are all designed into the module rather than improvised on site — cleaner, faster, more reliable.
Lightweight solar for constrained modules
Most MMC roof structures carry a standard in-roof PV system (12-15 kg/m²) without difficulty. Where roof loading is constrained — lightweight steel-frame modules, rooftop additions, or modules with long unsupported spans — lightweight panel options solve it:
- •Frameless glass-glass modules — lower weight per watt, bonded rather than clamped
- •Lightweight composite panels — ~6-8 kg/m², roughly half the weight of standard glass modules, for severely weight-constrained applications
- •Flexible/thin-film for curved or membrane roofs — niche, but available for non-standard modular roof forms
Lightweight solar for modular buildings is a particular ask in London, where modular build-to-rent, student accommodation and council modular housing schemes often sit on lightweight steel-frame modules. We supply both standard and lightweight in-roof systems to the module assembly line.
The factory pre-fit programme
Our modular solar programme follows four stages, integrated with the manufacturer\'s production line:
| Stage | Where | What happens |
|---|---|---|
| 1. Design | Pre-production | Array sizing per module type, SAP/HEM modelling, cassette spec |
| 2. Factory fit | Module factory | In-roof cassette installed on roof module, weatherproofing tested |
| 3. Site install | On site | Module craned in, 2-hour final electrical connection per plot |
| 4. Commission | On site | MCS certification, monitoring onboarding, warranty handover |
For the full case for MMC under the Future Homes Standard, read our timber frame and FHS pathway article. For the volume-developer procurement model, see bulk procurement pricing.
To discuss factory pre-fit solar for your modular or MMC programme, request a consultation.