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.
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
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:
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.
Castellum translated its roadmap into technical, operational, and procurement practices. Three key focus areas emerged:
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.
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.
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
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.
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:
By standardizing calculations across consultants and projects, One Click LCA ensures traceability, comparability, and internal ownership of carbon data across real estate portfolios.