Blästern 6, a 1940s-era office building in central Stockholm, is transitioning from district heating and cooling to an energy-efficient geothermal system equipped with natural refrigerant heat pumps, smart controls, and powered by hydroelectricity. Once complete, the building will operate nearly free of CO₂, standing as an important benchmark for historic building decarbonization in dense urban areas.
Customer: Newsec
Location: Gävlegatan 22, Stockholm, Sweden
Sector: Office
Floor area: 30,000 m²
Project type: Energy Machines™ Integrated Energy System with BTES
Heating capacity and % demand covered: 850 kW (99.7% of demand)
Cooling capacity and % demand covered: 800 kW (100% of demand)
Energy savings: 56.5% reduction in energy consumption (108 → 47 kWh/m²/year)
Operating cost reduction: More than 65%
Operational CO₂ emissions: Nearly zero (electricity sourced from hydroelectric power from the grid)
Additional environmental impact: 106 tonnes of CO₂ avoided by using an electric-powered drilling rig instead of diesel
Commissioning date: Spring 2026
Newsec, as property manager, has initiated a comprehensive energy retrofit of the 30,000 m² Blästern 6 office building in central Stockholm. The project replaces existing district heating and cooling with a high-efficiency geothermal integrated energy system, with Energy Machines providing the complete turnkey solution including design, integration, and implementation.
The new energy system will cover nearly all of the building’s heating and cooling needs using hydroelectricity and on-site energy storage, significantly reducing both environmental impact and energy costs. The upgrade will cut the building’s energy consumption by more than half, lower annual operating costs by more than 65%, and reduce the property's operational CO₂ emissions to nearly zero.
The installation includes 40 boreholes, each drilled to a depth of 350 meters, located in the building’s basement parking garage. These form the foundation of a Borehole Thermal Energy Storage (BTES) field used to store thermal energy across seasons. Heating and cooling are delivered via eight Enrad heat pumps that use propane (R290), a natural refrigerant.
With a heating capacity of 850 kW and cooling capacity of 800 kW, the fully electric system is designed to meet 99.7% of the building's heating needs and 100% of its cooling. Later project plans include the addition of an electric boiler for backup redundancy, eliminating the need for district heating to cover the minimal peak heating demand.
Rather than constantly generating heating or cooling as in a typical HVAC system, the Energy Machines™ Integrated Energy System is designed to move and reuse thermal energy between the building and the BTES ground storage. This includes capturing and storing waste heat generated inside the building — including from equipment, lighting, or people — in order to reduce the total energy demand and maximize the value of every kilowatt used.
Designed with Energy Machines’ modular system approach, the project is designed using standardized, pre-programmed modules of energy system components to ensure high performance, faster installation, easier commissioning, and simplified long-term maintenance.
To reduce emissions across the entire project lifecycle, drilling is being carried out using an electric-powered air compressor from Atlas Copco and an electric drill rig by Team Wessman AB. This innovation avoids the use of diesel-powered compressors, eliminating an estimated 106 tonnes of CO₂ emissions during drilling alone.
Blästern 6 is another step in Energy Machines’ mission to help transform Sweden’s buildings into energy machines — properties that generate, store, and reuse their own energy. This retrofit in-progress proves that even older buildings can become leaders in energy performance and sustainability.
