Science-based targets in real estate: How Castellum is aligning net-zero ambitions with operational systems

Why science-based targets in real estate matter

Real estate contributes approximately 39% of global energy-related carbon emissions, with the majority linked to building operations and materials. As climate regulations intensify and expectations for environmental reporting increase, real estate developers and property owners must adopt measurable and verifiable decarbonization pathways.

Castellum is one of the largest listed commercial property developers in the Nordics. With a portfolio spanning new construction, renovations, and operations, the company has committed to achieving science-based emissions reductions in line with the 1.5°C target of the Paris Agreement.

Scaling carbon transparency across a complex real estate portfolio

Castellum’s science-based target, approved by the Science Based Targets initiative (SBTi) in 2018, addressed Scope 1, 2, and 3 emissions. By 2021, climate calculations revealed that in order to drastically decrease the emissions, the focus had to be on the majority of emissions which originated from construction and refurbishment activities. The company faced a fundamental shift: decarbonization at a construction level is required even more than clean energy. This revelation demanded end-to-end transformation.

“We realized it wasn’t enough to just reduce operational emissions. Our Scope 3 — mainly construction and tenant adaptations — represented the bulk of our climate impact. That’s where we needed to act faster and more decisively.”

- Maria Perzon, Group Sustainability Manager, Castellum

A three-part science-based roadmap with built environment alignment

Following the release of the SBTi’s building sector framework in late 2023, Castellum restructured its emissions reduction targets into a more granular and actionable framework:

• Property management: Targeting reductions in energy use, refrigerants, and tenant electricity
  
  
• New construction: Applying carbon intensity thresholds by asset class
  
  
• Purchased goods and services: Covering emissions from refurbishments, interior adaptations, and property services
  
  

Castellum established 2023 as the new base year, adopting Nordic-specific location-based emission factors and measuring performance using intensity metrics (kg CO₂e/m²), instead of absolute volumes, to reflect portfolio changes more precisely.

Implementation: Systems, modelling, and engagement across functions

Castellum translated its roadmap into technical, operational, and procurement practices. Three key focus areas emerged:

1. Operational energy optimization

• Reduced operational emissions by 84% since 2007
  
  
• Achieved a 33% reduction in energy use
  
  
• Completed over 100 project optimizations since 2020
  
  
• Major solar initiatives, including one of the Nordics’ largest rooftop PV systems and to date 120 PV plants
  
  

2. Carbon caps for new construction

• Fixed embodied carbon thresholds for projects finalized 2030 (A1-A5, NollCO2 scope):
  
  
  • 190 kg CO₂e/m² for offices
    
    
  • 180 kg CO₂e/m² for logistics buildings
    
    

• Castellum shifted from percentage-based targets to fixed caps, providing clarity for procurement and design teams
  
  

3. Circularity in refurbishments and tenant adaptations

• Refurbishments and tenant adaptations must achieve 50 % decreased emission
  
  
• Projects  must prioritize material reuse and layout preservation
  
  
• Some adaptations achieved 98% material reuse by weight
  
  

To ensure execution fidelity, Castellum embedded climate KPIs in quarterly reporting and board-level incentives. Internal alignment was reinforced with 40+ sustainability webinars for teams across the business, the majority focusing on climate and reuse.

One Click LCA: A standardized approach to life-cycle carbon tracking

Although Castellum does not apply One Click LCA tools internally, it requires external consultants to use them across projects. This approach consolidates results into a centralized LCA portfolio, ensuring consistent calculations and enabling traceable, portfolio-level comparisons. The tools are applied at different stages of the process — from early-stage modeling with Carbon Designer 3D, to whole-building LCAs that comply with EN 15978 and EU Taxonomy, and through EPD integration that supports low-carbon procurement.

By standardizing LCA tools across its pipeline, Castellum ensures project comparability, internal data ownership, and alignment with SBTi requirements.

From technical targets to systemic change

Castellum’s roadmap is recognized as a best-practice approach in the real estate sector, combining technical rigor with organizational alignment. Notably, the company was listed in the Financial Times’ Europe’s Climate Leaders in 2025, reflecting both their leadership in transparency and performance.

“You need tools, routines, and governance. But also people. From our project teams to our suppliers, it only works if they’re engaged and equipped.”
— Maria Perzon, Group Sustainability Manager, Castellum

Lessons for other real estate developers

Science-based targets provide structure — but results require systems. Castellum’s success demonstrates the importance of operationalizing decarbonization through data integration, internal governance, and team training. As regulations evolve and investor expectations rise, replicating such systems will be essential for real estate portfolios pursuing credible, measurable carbon reductions.

One Click LCA for real estate

Life-cycle carbon accounting is now essential for real estate portfolios targeting net zero. One Click LCA supports this by providing tools for real estate professionals to help integrate carbon transparency across new developments, refurbishments, and tenant fit-outs:

• Early-stage modeling with Carbon Designer 3D to assess carbon intensity by asset type, even from limited data.
  
  
• Whole-building LCAs aligned with EN 15978, enabling standardized tracking across projects and integration with GRESB or EU Taxonomy requirements.
  
  
• EPD-integrated procurement, with access to 300,000+ environmental product declarations (EPDs) for specifying lower-impact materials.
  
  
• Refurbishment and fit-out calculations, including material reuse modeling, to meet carbon targets like Castellum’s.
  
  

By standardizing calculations across consultants and projects, One Click LCA ensures traceability, comparability, and internal ownership of carbon data across real estate portfolios.