Improving energy efficiency and comfort in Swedish apartment buildings: the Carlavägen residential block

• Project: Carlavägen buildings 

• Building: 12 apartments built in 1947 

• Country: Sweden 

• Technology: cloud-based optimisation and control solution + dynamic balancing 

• Results: 20% of energy savings (20,359 kWh saved over two heating seasons) 

Improving the energy performance of existing residential buildings has been challenging across the different Member States, particularly where outdated heating systems limit efficiency and occupant comfort. This case study by Danfoss presents a multi-family residential building in Eskilstuna, Sweden, where the combination of digital heating optimisation and system-level balancing enabled significant energy savings while improving indoor comfort. The example demonstrates how targeted interventions in existing building systems can deliver measurable performance improvements, even in older building stock.

The challenge: Discomfort and inefficiency in an old residential building

The Carlavägen building block in Sweden, managed by HSB Södermanland, exemplified the challenges facing many European residential buildings. Built in 1947 and later renovated with district heating, the property continued to suffer from inefficiency and poor indoor comfort. Limited apartment sensors meant poor visibility into indoor conditions, while the heating curve—which required manual adjustment based on outdoor temperatures—resulted in inconsistent indoor temperatures and excessive energy consumption.

To address these challenges, the project set out to ensure stable, comfortable indoor temperatures across all 12 apartments while minimizing energy consumption. The goal: enable more cost-effective building management and generate better building performance data.

The solution: digital controls and dynamic balancing 

The project followed a two-step approach. First, a cloud-based AI solution optimized the building’s existing substation controller with no additional hardware required. This system enabled remote monitoring and control, leveraging operational, weather, and indoor measurement data to continuously fine-tune heating supply temperatures. The result was improved visibility into indoor conditions, reduced manual intervention, and a more efficient, responsive heating system.

In the second phase, the team implemented dynamic hydronic balancing to enable further energy savings. Existing valves and thermostatic radiator controls were replaced with components designed to maintain stable pressure and ensure optimal heat distribution across all apartments. This eliminated remaining temperature imbalances, guaranteed efficient operation under varying load conditions, and further reduced energy consumption while sustaining consistent indoor comfort. 

Why this matters for the EPBD 

This project demonstrates several functions that are directly relevant to the Energy Performance of Buildings Directive (EPBD) requirements for technical building systems in residential buildings: 

• Continuous monitoring that tracks system efficiency and alerts managers to issues or maintenance needs; 

• Automated controls for optimal energy generation, distribution, storage, and use; 

• Hydronic balancing – dynamic balancing valves improve flow, pressure and apartment comfort. 

Rather than relying on manual operation or isolated measures, the project shows how combining digital control with system-level optimisation can deliver practical, measurable improvements in existing residential buildings. 

Reported impact 

After each phase of the project, the results showed a significant improvement in energy efficiency, resulting in measurable savings: 

• 20% of energy savings (20,359 kWh over two years) 
  • 10.9% of energy savings after the first phase (11,136 kWh total in a year) 
  • Additional 10.2% of energy savings after the second phase (9,223 kWh total in the second year) 

• Setpoint reduced by 1.5º without changing the comfort levels 

• Improved comfort for the tenants 

Find out more  

Watch eu.bac’s webinar recording for a complete overview of this project.   

Reach out to Jon Berggren (Country Head of Business Solutions in Sweden for Danfoss) for more information.    

Read more about the project here.