Transforming an Ageing Office Complex into a Fully Electric, Future-Ready Urban Hub
Montgomery Parc demonstrates how smart electrification can transform an ageing, fossil-fuel-dependent building into a high-performing, future-ready asset without demolition.
Located at the gateway to Brussels' European District, the project converted a closed and inefficient office complex into a vibrant mixed-use destination powered entirely by electricity and aligned with Europe's climate ambitions.
By retaining and upgrading the existing structure, the project combined deep energy renovation, full electrification, renewable energy generation and climate adaptation measures to create a resilient, low-carbon building that serves both occupants and the wider community.
Project Overview
Project: Montgomery Parc
Location: Brussels, Belgium
Building Type: Mixed-use refurbishment with offices, retail and kindergarten
Status: Completed in September 2025
BGBC Members Involved: B2ai, Kolmont, SuReal, Cordeel Group
Project Milestones
Fossil Fuels: 0% - Completely gas- and oil-free heating and cooling
Office Energy Demand: CEP = 57.96 kWh/m²/year which is nearly three times lower than the Brussels regulatory cap of 165.72
On-Site Renewables: 400 kWp rooftop solar PV installation
Embodied Carbon: 205 kg CO₂e/m² (OneClick LCA Label A)
Certifications: BREEAM Outstanding, Precertified DGNB Platinum & WELL Platinum
The Challenge
The original complex faced several common challenges experienced across Belgium's building stock:
- Poor energy performance and high operating costs.
- Dependence on fossil-fuel heating and hot water systems.
- Low occupant comfort.
- Misalignment with Brussels' low-carbon building requirements.
- A risk of premature demolition despite a structurally sound building frame.
The project team set out to prove that deep renovation and smart electrification could unlock better outcomes than demolition and rebuild, while preserving the value already embedded in the existing structure.
The Smart Electrification Approach
Montgomery Parc follows the Smart Electrification Framework that is rooted in European energy policy and structured around four pillars: Efficiency First, Smart Electrification, Renewable Energy and Grid Readiness.
1. Efficiency First
The Concept: Minimising the building's energy demand at the source before upgrading the mechanical systems.
Technical Execution: By retaining and optimising the existing concrete structure, the project drastically minimised its upfront carbon footprint (embodied carbon) to 205 kg CO₂e/m², sitting well below the Western European average.
The Data: The building envelope underwent a deep upgrade to achieve exceptional thermal performance, reaching U-values of 0.15 to 0.20 W/m²K and an airtightness of n₅₀ = 0.79 vol/h under EN 13829 (Method A, full building). To avoid traditional fossil-based insulation, the team successfully qualified and deployed recyclable alternatives like recycled glass wool.
Policy & Future Value: The interior space is built on a 1.2 m modular grid, guaranteeing effortless spatial adaptability so the building can be reconfigured in the future without structural demolition work.
2. Smart Electrification
The Concept: Completely replacing combustion-based heating systems with highly efficient, electrified alternatives.
Technical Execution: Legacy fossil-fuel boilers were completely decommissioned. High-performance air-to-water heat pumps were selected to provide space heating, cooling, and domestic hot water across the mixed-use units (offices, retail, and a kindergarten).
The Engineering Compromise: While a geothermal borefield was initially evaluated, it was ruled out to protect and preserve the mature, historic trees on site. The air-to-water heat pumps were carefully integrated on the roof to ensure they remained entirely invisible below the strict regulatory roofline and met stringent acoustic parameters to protect the kindergarten below.
The Data: Verified using the official Brussels EPB framework (2020 method, PEB v15.5.2), the 26,436 m² office unit achieved compliance across all primary energy consumption metrics.
3. Renewable Energy
The Concept: Powering the electrified infrastructure with green electricity generated right on the building.
Technical Execution: A massive 400 kWp rooftop solar PV array was installed.
Policy & Future Value: By covering a significant portion of its operational demand via on-site solar, net grid draw is substantially reduced. For any remaining electricity needs, a 100% electric building means its operational carbon footprint automatically tracks toward zero as the Belgian power grid systematically decarbonises over time.
4. Grid Readiness and Resilience
The Concept: Preparing the building to interact intelligently with the power grid while enhancing the local urban environment.
Technical Execution: The building utilises smart energy management systems (EMS) and demand-response readiness to dynamically balance electricity load and prevent net overload.
Climate Adaptation: The building acts as an active sponge for the city. It features green and retention roofs to capture rainwater for greywater reuse and irrigation, alongside a 5,500 m² urban microforest. This microforest boosted the Biotope Area Factor (BAF+) by 144%, significantly mitigating the local urban heat island effect.
Modal Shift: To lower commuter emissions, soft-mobility infrastructure was built into the site, including 70+ secure bicycle parking spaces (with cargo-bike slots, showers, and lockers) right next to the Montgomery public-transport hub.
Beyond Electrification: Climate Adaptation and Biodiversity
Montgomery Parc shows that building electrification can deliver multiple benefits beyond carbon reduction.
The project includes:
- Green and retention roofs that capture rainwater for reuse.
- A 5,500 m² microforest.
- A 144% increase in Biotope Area Factor (BAF+).
- Nature-based solutions that reduce urban heat island effects and stormwater runoff.
Active mobility was also prioritised through:
- More than 70 bicycle parking spaces.
- Showers and lockers.
- Direct connections to Brussels' Montgomery metro, tram and bus hub.
Results and Impact
Outstanding Energy Performance
The office component achieved:
57.96 kWh/m²/year Primary Energy Consumption (CEP)
compared to the regulatory threshold of:
165.72 kWh/m²/year.
100% Fossil-Free Operation
By combining a high-performance envelope with fully electric systems, Montgomery Parc eliminated fossil-fuel dependence altogether. The building's operational carbon footprint now improves automatically as Belgium's electricity grid continues to decarbonise.
Lower Embodied Carbon
Retaining the original structure delivered significant material savings and achieved:
205 kg CO₂e/m² embodied carbon
earning a OneClick LCA Label A rating.
Renewable Energy Generation
The installation of 400 kWp rooftop solar PV reduces net electricity consumption and supports energy independence.
Leading Sustainability Certifications
The project achieved:
- BREEAM Outstanding
- DGNB Platinum (pre-certified)
- WELL Platinum (pre-certified)
- Alignment with the EU Taxonomy framework.
Social Value Creation
Rather than remaining an underused office complex, Montgomery Parc became a mixed-use destination combining:
- Offices
- Retail functions
- A kindergarten
- A green courtyard.
Long-term attractiveness, adaptability and value for investors.
Beyond reducing carbon and energy demand, the transformation strengthens the long-term value and attractiveness of the building. A new meeting pavilion at the heart of the garden, direct access to more than 5,000 m² of landscaped gardens, flexible office spaces, smart building technologies and a strong focus on health and wellbeing are complemented by terraces, sports and coworking facilities and childcare. Together with its strategic location close to Brussels’ European Quarter and major public transport connections, these qualities create an attractive working environment for occupants while supporting the building’s long-term adaptability and value for investors.
Key Lessons for the Sector
1. Prioritise the Envelope Early:
Achieving tight envelope performance (n₅₀ = 0.79 vol/h) reduces thermal demand first. This allows for smaller, more cost-effective heat pump sizing, reducing both upfront CapEx and long-term running costs.
2. Commit Fully, Avoid Hybrids:
Retaining a residual gas or fossil-fuel backup system creates an expensive 'fossil lock-in' that is costly to remove later. Full electrification satisfies strict EU Taxonomy criteria and simplifies plant room maintenance.
3. Front-Load Compliance Modeling:
Do not treat energy modeling as a checkbox exercise at project completion. Running high-fidelity compliance models (like PEB v15.5.2) early in the design cycle allows teams to actively optimise window-to-wall ratios and insulation strategies before construction begins.
Why This Matters
Montgomery Parc demonstrates that smart electrification is not simply about replacing gas boilers with heat pumps. It is about creating buildings that are more efficient, more resilient, more attractive to occupants and investors, and better prepared for a net-zero future. Through deep renovation, full electrification, renewable energy integration and climate adaptation measures, the project provides a compelling blueprint for the transformation of Belgium's existing building stock.
"The cleanest building is often the one that already exists.
Upgrade it, electrify it, and prepare it for the future."
B2Ai is a multidisciplinary team of 140 architects, engineers, interior designers and urban planners in Brussels, Ghent, Roeselare and Antwerp working together to build a sustainable society with a particular focus on people and the environment.
Cordeel Group is a family-owned Belgian construction group. We are an ecosystem of innovative companies focused on sustainable construction, circularity, and the energy transition. As a Core Founding Partner of the Belgian Green Building Council, we are committed to making the sector more sustainable by sharing knowledge and best practices. Through our projects, we strive to set a strong example and drive the transition to a greener built environment.
Kolmont is a forward-thinking family business that develops sustainable real estate with a focus on future generations. Our projects go beyond functionality and aesthetics, fitting into a broader vision where long-term values take center stage. Through innovative technologies and climate-resilient measures, we strive for maximum energy efficiency and a minimal ecological footprint. In this way, we contribute to a future-proof society, aligning our climate ambitions with the mission of the Belgian Green Building Council.
SuReal is a consultancy firm that supports companies and government agencies in making buildings, city projects and companies more sustainable while keeping in mind the well-being of its occupants. Our experts provide sustainability, circularity and overall ESG advice and support from concept to delivery. Joining the Belgian Green Building Council allows us to drive change and co-create a future-proofed society.