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The Rue de Spa building project consists of the demolition-reconstruction of 8 modular office levels, from 200m² to 900m² each. The building reaches the Passive-house standard and is also BREEAM Excellent certified. The prefabrication of facades and the reduction of cold needs with residual needs covered by a chiller group equipped with a free chilling, are the strong points of the project, as well as the installation of green roofs, the control of the airtightness, soft mobility (local bicycles and showers) ...

The Oxygen Office Building project, ideally located in the city of Brussels between the Royal Park and the Squares District, and between the Arts-Loi and Maelbeek metro stations, aimed the construction of a new low footprint office building replacing one that had become obsolete.


Thanks to a staggering of the roofs, the new building joins the different reference heights of neighboring buildings. The roof also serves of support for a green roof as well as for a high yield photovoltaic production (112m² - 22.5 kWp).


The Passive Building Standard criteria are respected. The prefabricated façade envelope is composed by timber curtain-wall modules, filled with cellulose insulation, and covered with white aluminum cladding on the outside. Energy needs are met through efficient systems, including a condensing gas boiler and a hybrid refrigeration unit running on rainwater. A centralized system of regulation has been set up and allows consumption monitoring.


The construction is designed in such a way that it allows changes of use and ease for renovation in the future. In addition, the project aims to entice soft mobility offering +30 places for bicycle parking and electric charging points for bicycles and cars.


Rue de Spa 8-10-12, 1000 Bruxelles

  • Programme: Office building
  • Client : Fonsny nv /  ALIDES (groupe MAES)
  • Architect: Conix Architects
  • Building services consultant: ARCADIS Belgium sa
  • Brut floor area: 6055 m²
  • Budget before taxes: 1467 € /m²
  • Delivered: 2017/02
  • Bâtiment exemplaire building : 2013 [231]
  • Energy consumption:
  • Space Heating Energy Demand: 10 kWh/m². year (standard building: 106 kWh/m².year)
  • Air Tightness Value : 0.48

Author(s) information


Conix Architects / ARCADIS Belgium sa

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Operational date

Wednesday, 1 February, 2017

Relevant tools

PHPP 2007: Passive House Planning Package

Source of funding