The Hepokorpi substation is Finland's largest indoor switchgear facility. It comprises 400 kV and 110 kV gas-insulated indoor switchgear, two 400 kV main transformers housed in buildings, and three landscape pylons. It serves the local power grid and a large data centre under construction in the area, from which recovered waste heat is used in Espoo's district heating production.

Reflecting the forest’s spatial character and terrain, the substation’s structures and spaces vary in terms of how open or closed they are. The vibrant dark green glazed ceramic cladding on the facades, and its layered, partly free-form structure, are based on the topography, porosity, and colours of the forest landscape. Inside the switchgear building, windows and glass doors allow long views through the spaces and outwards.

This is the first substation in Finland where the frame of the main equipment halls is made of solid wood. The load-bearing columns and beams are in glulam, with the wall and roof panels in cross-laminated timber. High-quality in-situ concrete structures complement the wooden structures in other parts of the facility.

The hyperboloid landscape power line structures are part of the mathematical landscape of the power lines that cross the site. Their spatial and porous form seeks to harmonise with the buildings’ architecture. Functionally and visually, the forest landscape and the utilitarian landscape of power lines meet at the substation site.