The Future Buildings Standard requires solar PV on new non-domestic buildings, with PV array area equal to 40% of the building's foundation area for both side-lit and top-lit zones (consultation response, para 3.11, p18). This makes PV a key compliance factor in the notional building specification for most new non-domestic projects.
The 40% PV rule
The FBS policy sets a flat PV coverage requirement: 40% of the building's foundation area, regardless of whether zones are side-lit or top-lit (consultation response, para 3.11, p18). This applies equally to offices, warehouses, schools, and retail buildings.
The current NCM 2021 implements this differently. Its weighted formula (Equation 9) calculates PV as 20% of foundation area for side-lit and unlit zones, and 40% for top-lit zones, each proportioned by their share of total floor area. The 2026 NCM (not yet published) will implement the flat 40% rule as stated in the consultation response.
In practice, the PV requirement is expressed as a minimum installed capacity in kWp, calculated at 0.2 kWp per m² of PV array area (NCM 2021, para 81).
Exemptions and special cases
The PV requirement is not absolute. The following exemptions and reductions apply:
- Higher-risk buildings – HRBs are exempt from the PV requirement due to the practical difficulties of installing and maintaining panels on tall buildings
- Buildings with insufficient roof area – where the available roof area is genuinely insufficient (e.g., due to overshadowing, plant equipment, or structural constraints), a reduced provision may be accepted
- Listed buildings and conservation areas – where planning constraints prevent PV installation
- Heat pump reduction – if any HVAC system provides space heating using a heat pump, the PV array is reduced pro-rata by the proportion of heating demand met by the heat pump. If 100% of heating is from heat pumps, the notional building has no PV (NCM 2021, para 83)
Where an exemption applies, the SBEM calculation still determines the TER/TPER from the notional building (which includes PV). The actual building must meet these targets through other means – typically improved fabric, more efficient systems, or alternative renewable energy sources.
Practical implications by building type
Offices
Offices are predominantly side-lit buildings. Under the FBS policy, they require PV covering 40% of the foundation area, the same as any other building type (consultation response, para 3.11, p18). Note that the current NCM 2021 calculates only 20% for side-lit zones (Equation 9) - the 2026 NCM will implement the flat 40% rule. If the office uses 100% heat pump heating, the notional building has no PV requirement at all (NCM 2021, para 83). Typical flat-roofed offices generally have sufficient roof area where PV is needed.
Warehouses and industrial
Warehouses are typically top-lit, so the PV weighting is 40% of foundation area for top-lit zones. Large warehouse roofs offer excellent PV potential, and many developments may exceed the minimum for additional energy generation. However, structural loading from PV panels must be considered in roof design.
Schools
Schools typically have sufficient roof area but may face budget constraints. The FBS impact assessment includes cost estimates for PV installation across building archetypes, showing that the additional capital cost is offset by operational energy savings over the building's lifetime.
Retail
Retail buildings vary significantly – a large supermarket with a flat roof will easily accommodate PV, while a small high-street unit may face constraints. Where roof area is limited, the SBEM calculation allows compensation through other energy efficiency measures.
Cost implications
The government's impact assessment estimates the cost of compliance across building types, including PV installation. While PV adds to upfront construction costs, the analysis shows a positive net present social value when operational energy savings and carbon reductions are included (FBS Impact Assessment).
How PV affects the compliance calculation
Solar PV reduces both the BER and BPER of the actual building by offsetting grid electricity consumption. In the SBEM calculation, PV is modelled based on panel area, orientation, tilt angle, and efficiency. The generated electricity is deducted from the building's total energy consumption.
Because the notional building includes PV, omitting it from the actual building means the TER and TPER must be met entirely through other measures – which is significantly more challenging and often impractical.
Frequently Asked Questions
How is the solar PV requirement calculated under the FBS?
The FBS policy requires PV array area equal to 40% of the building's foundation area for both side-lit and top-lit zones (consultation response, para 3.11, p18). The current NCM 2021 implements this using a weighted formula (Equation 9) with 20% for side-lit and 40% for top-lit zones - the 2026 NCM will implement the flat 40% rule. If 100% of heating is from heat pumps, the notional building has no PV at all (NCM 2021, para 83).
Are higher-risk buildings exempt from the solar PV requirement?
Yes. Higher-risk buildings (at least 18 metres tall or 7 storeys with 2+ residential units) are exempt from the PV requirement due to practical difficulties of installation on tall buildings. However, they must still meet the TER and TPER through other measures.
What if my building doesn't have enough roof space for PV?
Where roof area is genuinely insufficient, a reduced PV provision may be accepted. The SBEM calculation allows compensation through improved fabric, more efficient systems, or alternative renewables. Document the constraints in the compliance report.