Rejlers helps demonstrate viability of reuse for building renovations

Reference

Rejlers has contributed to the complete renovation of Grensen 9B, a 1970s office building in Oslo that has been redesigned to show how reuse and circular solutions significantly reduce environmental impact while remaining economically viable.

Reference 25.1.2026

About the project

CHALLENGE

To fully refurbish an older office building in central Oslo while meeting modern technical requirements and adhering to circular building principles with a strong focus on reuse.
SOLUTION

Rejlers contributed with detailed design of new telecommunications and electrical installations, with a particular focus on reusing existing cables, electrical cabinets and cable trays wherever technically feasible.
RESULT

The project achieved 97.3% reuse of existing building materials and reduced material-related greenhouse gas emissions by 93%, demonstrating that circular refurbishment can be both sustainable and cost-effective.

Built in 1978, Grensen 9B is a six-floor office building in central Oslo owned by Oslo Pensjonsforsikring and the Pension Fund for the Health Enterprises in the Capital Region (PKH). In collaboration with Mad Arkitekter, the building was recently fully renovated, in line with circular building principles.

The main strategy at Grensen 9B was to preserve and reuse as many existing materials as possible, from concrete and steel to ceiling tiles and ventilation ducts. Rejlers contributed to the project by providing detailed designs and calculations for the installation, by electrical contractor Romerike Elektro, of Grensen 9B’s new electrical and telecommunication systems.

“The building was planned to undergo a complete renovation as a circular reuse project,” says Christian Ellefsen, Electrical Engineering Consultant, Rejlers Norway. “This included technical installations and therefore all the electric and telecommunication systems. We therefore made new designs for the electrics and telecommunications that met modern standards and supported the new layout of the building.”

Reuse was also a primary focus for Rejlers’ work in the project. “The requirement to reuse materials is actually unusual,” says Ellefsen. “But we were able to reuse electric and telecommunication cables as well as steel racks, used to organise and mount equipment like servers, routers and switches, and steel cable trays which are used to securely support and organise electric and communication cables.”

Grensen 9B’s renovation included the reuse of 97.3 percent of existing above-ground building materials. Greenhouse gas emissions related to materials were reduced by 93% compared to office building averages.

“This pioneering project demonstrated a strong will and ability to challenge and break away from established ways of thinking and working,” says Ellefsen. “It proves that reuse can achieve sustainability goals while also being economically viable. It has been a pleasure to work on and should help lead to a future where reuse is increasingly the norm in construction projects.”