21/05/2025

With increasingly stringent regulatory requirements, solarizing buildings is no longer an option—it’s a necessity. By 2028, many new constructions and major renovations will be required to incorporate solar systems to comply with urban planning laws and meet energy transition goals.

This article will help you understand the relevant legislation, anticipate deadlines, and most importantly, identify concrete solutions—even if your roof cannot accommodate standard solar installations.

Understanding the solarization requirement: legal framework and timelines

Three key laws you need to know

In recent years, the legal framework around building solarization has tightened significantly. If you own or manage a logistics, commercial, or office site, you are now directly impacted by a growing list of regulations.

Three main laws shape today’s regulatory landscape:

  • The Tertiary Decree (2019): Requires tertiary-use buildings over 1,000 m² to reduce energy consumption by 40% by 2030, 50% by 2040, and 60% by 2050, compared to a baseline year. These goals strongly encourage the use of renewable energy, particularly solar power.

 

Solarisation entreprises

 

  • The Climate and Resilience Law (2021): Broadens and clarifies solarization requirements for new or heavily renovated buildings, introducing minimum surface thresholds and energy coverage requirements.
  • The APER Law (2023) – Acceleration of Renewable Energy Production: For new extensions or major renovations, certain buildings—especially those with tertiary use—must install renewable energy systems or green roofs on at least 30% of the roof. This threshold increases to 40% in 2026 and 50% in 2027.

 

What types of buildings are affected?

Mandatory solarization doesn’t apply to all construction or renovation projects. It primarily targets commercial uses and large footprints, with a clear logic: the larger your building or lot, the greater your contribution to renewable energy production must be.

Solarisation bâtiment tertiaire

Affected construction types include:

  • New tertiary, industrial, commercial, artisanal, or office buildings with a footprint over 500 m²
  • Extensions or heavy renovations of existing buildings exceeding that same area
  • Public buildings such as hospitals, schools, gyms, or cultural venues

Heavy renovation refers to work affecting the structure, stability, or load-bearing elements (roof, frame, foundations…), which automatically triggers the requirement, even for older buildings.

Timeline of Requirements Through 2028

The rollout of solarization mandates follows a gradual schedule to give stakeholders time to prepare. But beware—some deadlines have already passed, and others are fast approaching.

Key dates to remember:

  • January 1, 2024:
    → All new buildings over 1,000 m² (offices, retail, industry…) must include a renewable energy system or an equivalent (e.g., high-performance green roof).
  • July 1, 2026:
    → Minimum coverage increases to 40%, then to 50% the following year.
  • January 1, 2028:
    → All existing buildings over 500 m², regardless of construction date, will be affected.
    → Law also applies to older tertiary, warehouse, or industrial buildings.

This timeline might seem generous, but it doesn’t account for real-world constraints—structural audits, urban planning approvals, financing, and system selection often take months, even over a year. Waiting until 2027 could leave you unprepared by 2028.

Solarization rules for existing, new, or renovated buildings

What area must be solarized? Understanding the calculation

A key concept is “building footprint”, which defines whether your building is subject to the law and how much surface must be equipped with solar panels or equivalent systems.

The footprint refers to the ground area occupied by the building, including annexes, but excludes roof overhangs and ground-level terraces.

Based on this, the law requires a minimum coverage rate of the roof with renewable energy systems:

  • 30% of the roof for most projects
  • Up to 50% for specific projects

Example:
A new logistics warehouse

  • Footprint: 1,900 m²
  • Roof area: 2,000 m²
  • Required solar surface: 30% = 600 m² of photovoltaic modules

Important: Only the actual module area counts. Circulation zones, technical spaces, and walkways between panels are excluded.

 

What are the penalties for non-compliance?

Solarization is a legal obligation, not a guideline. Failure to comply can lead to administrative or financial penalties.

Potential consequences:

  • For new buildings:
    A non-compliant building permit can be denied. Construction cannot proceed until solar requirements or an approved alternative (like a green roof) are integrated.
  • For existing buildings from 2028 onward:
    Specific penalties will be outlined in upcoming texts, but fines and formal notices for non-compliance are expected.

Failing to anticipate could result in cost overruns, project delays, or inability to meet deadlines.

 

What are the options? Solar, green Roofs, or a hybrid solution

The law allows flexibility, provided the solution meets energy performance standards. While photovoltaic (PV) panels are the most common choice, alternatives may be considered for complex or constrained sites.

You may choose:

  • A PV solar installation
  • A green roof or green canopy focused on thermal insulation and biodiversity
  • A combined solution (“biosolar roof”) mixing both

Solar photovoltaics: the most direct option

In most cases, installing a solar power system on the roof  is the simplest solution. Benefits include:

  • Local electricity production (for self-consumption or resale)
  • Compliance with renewable energy targets
  • Economic value, especially with feed-in tariffs like S21

Ground installations may not always qualify unless directly linked to the building—always verify with urban planning authorities.

Green Roofing: a regulated alternative

Permitted in dense urban areas, protected zones (e.g., near historical monuments), or when structural limits prevent solar panels. To be accepted, green roofs must:

  • Provide high-performance insulation
  • Retain rainwater
  • Support urban biodiversity
  • Be justified in the urban planning permit application

This isn’t a loophole—it’s a regulated, conditional alternative.

Végétalisation toiture

 

Biosolar roofs: a growing hybrid trend

A growing number of companies combine solar panels and vegetation to meet both energy and environmental goals. This mixed approach:

  • Covers partial solarization requirements while improving insulation
  • Reduces runoff and soil sealing
  • Enhances environmental branding, especially in high-profile areas

Feasibility studies are essential to assess technical, legal, and energy constraints before choosing a solution.

Standard solar panels: a dead end for some buildings

Structural and architectural challenges

Not all buildings can accommodate traditional solar systems due to:

  • Low-slope or lightweight roofs (common in warehouses/logistics)
  • Metal frames sensitive to added weight
  • Special membranes that can’t be drilled or heavily ballasted
  • Rooftop equipment (vents, ducts) limiting usable space
  • Protected zones with strict roof modification rules

In these cases, solar panel installation may be unfeasible.

Hidden costs of heavy renovation

These structural limits often lead to costly upgrades, including:

  • Frame reinforcement
  • Complete waterproofing replacement
  • Temporary operational shutdown
  • Engineering and structural studies

Lightweight solar panels: an alternative solution

Designed for complex roofs

Lightweight solar panels are made for fragile or constrained rooftops. They are ideal for flat roofs on logistics, industrial, commercial, or office buildings.

Benefits:
→ Compliance without structural modification
→ Installation on previously ineligible buildings

Panneau solaire léger Heliup

Quick, adhesive-based installation

These panels are glued directly to waterproofing membranes using built-in adhesives:

  • No roof drilling = preserved waterproofing
  • No ballast = minimal added weight
  • Quick installation = fewer disruptions

Non-adhesive versions also exist for customized mounting, offering flexibility for complex renovation projects.

Discover Heliup’s Skyton® panels for flat roofs

Economic, regulatory, and environmental benefits

Self-consumption and energy savings

Solarization isn’t just an obligation—it’s an opportunity to lower your energy costs:

  • Produce local electricity
  • Reduce grid dependency and tariff exposure
  • Stabilize energy budgets
  • Earn income by selling surplus

ROI varies (5–20 years) depending on size, usage, and technology—but savings begin early.

Enhanced CSR Image

Solar adoption strengthens your environmental commitment, influencing:

  • Brand perception
  • Appeal to partners and clients
  • Success in ESG-focused tenders
  • Broader decarbonization strategies

Forward-looking companies are seen as modern, responsible, and innovative.

Subsidies and support for your solar project

Several public incentives can significantly reduce project costs:

  • S21 Feed-in Tariff:
    → For systems up to 500 kWc
    → Guaranteed electricity resale price for 20 years
  • Self-Consumption Bonus:
    → For individuals or companies selling surplus
    → Up to 100 kWc projects
  • Tax Incentives:
    → 20% VAT recovery for systems > 3 kWc
    → Reduced IFER (network tax) for systems > 100 kWc

Conditions apply, but these incentives can make a big difference in your budget.