Project Brussels, Belgium

Trebel - Wilfried Martens building

Geothermal drilling in the heart of Europe

Sector: Buildings

In collaboration with the general contractors BESIX et Jacques Delens, Franki Foundations carried out unseen geothermal works for the new European Parliament building on the “Trebel” site, at the corner of Trèves street and Belliard street, in the very center of Brussels.

Technical specifications

Geothermal drilling

  • 33 geothermal probes
  • up to 240 m deep


  • 100 anchors to support the existing diaphragm wall
  • Ø 175 mm
  • 12 to 21 m long
  • 120 to 330 kN tension

Driven tube piles

  • 200 piles to strengthen the soil on part of the construction job site
  • Ø 273 mm
  • 6 to 15 m long

BREEAM Excellent

For the « Wilfried Martens » building, which was meant to comply with the highest energy efficiency standards (BREEAM Excellent),

Franki Foundations performed the laying of geothermal probes, anchored into the bedrock, and up to a depth of 240 meters, a feat never achieved before in the Belgian capital! 
Indeed, geothermal probes are usually laid in the first layers of the soil, and multiplied when more calories are needed. But in this case, the available land was restricted (3.000 m²), so the probes had to be laid deeper in order to cover the heating and cooling needs of the future building.

The geothermal system will ensure heating of the building in the winter and cooling in the summer, for the most efficient energy balance. 

Blind drilling

"This was not an easy project” says Project Manager Dimitri Timbremont.

"At this depth, we had no detailed plan of the soil. So the start-up was very challenging because we had to refine the drilling methods during the drilling self. And we regularly faced some surprises. Nevertheless, this site was very interesting for us and we have gained extra experience with geothermal drilling, which is an activity we want to expand as it is closely linked to our standard deep foundations works.”

In collaboration with its Swiss partner Augsburger, the Franki team has updated its drilling technique according to the nature of the underlying soil in order to successfully drill as deeply as necessary.

Project details

Project name

Trebel - Wilfried Martens building

Area(s) of expertise

Governmental, Cultural and Religious, Offices


Geothermal drilling

Contract type



Brussels, Belgium


Franki Foundations


BESIX, Jacques Delens

Building Period

2014 - 2014


Jaspers Eyers & Partners


13 storey

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