782 Royale Belge credit Severin Malaud 4071

Office building "Souverain 25"

At the request of Cofinimmo, we investigated the feasibility of an energetic façade renovation of the Souverain 25 office building in Brussels.
  • Client: Cofinimmo

  • Timing: 2012 – 2013

  • Status: Executed

  • Advisors: Aluminium Centrum (sub-study stability joinery)

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The aim of the study was to find out whether the office building could be passive after a thorough facade renovation.

In parallel with our research, another study was conducted into optimisations of the technical installations using dynamic simulations of energy consumption.

Specifically, we had to define the measures down to the façade detail so that the building could achieve insulation quality K16.


We were asked to work out several scenarios ranging from a visually very radical façade renovation to one in which the façade aspect could be completely preserved. The report served as a working tool for discussions with the Heritage Agency. It was also asked to estimate the construction cost of the different façade scenarios.

Besides investigating potential thermal optimisations, we also examined the solar heat load and daylight penetration in order to determine a shading strategy and glass choice.

Building shell

The biggest part of the study was a very thorough analysis of the current building envelope. We did this using the as-built file, on-site tours, dismantlements and soundings. We left no m2 untouched.

The supporting structure made of Corten steel and concrete is on the outside. The impact of the perforation of this supporting structure through the building envelope was investigated by means of thermographic recordings.

The joinery, designed by Chamebel, was subjected to an equally thorough examination: thermal insulation value, structural load-bearing capacity of the joinery for use with triple glazing by the Aluminium Centre.

In the end, we ended up with a K-level of K93 for the building in its current state.

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Within the predefined scenarios, we explored the possibilities of thermally optimising each of the building envelopes. TRISCO software was an important tool here to solve the thermal bridges caused by external support structure. Principle detail drawings were prepared of the scenarios to visualise elaborated and calculated issues.

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The higher insulation and airtightness quality of the building envelope after renovation reduces energy consumption for heating, but will extend the cooling season and thus increase cooling costs significantly.

Correct glass selection with sufficient solar control properties is therefore important.

Using SunEye 210 (Solmetric), the shading of the external support structure on the façade was mapped in situ.

For different types of glass, our expert Martijn Vyncke analysed cooling loads, passive solar gains and savings on artificial lighting. From this, he concluded that glass with a good ratio of daylighting versus solar control glass had the best chance of succeeding in achieving the set goal.

We did not recommend a type of glass with a similar golden aspect.


Our study showed that an insulation quality K16 was not feasible within the proposed scenarios. Even in the most conservation-minded scenario where the facade aspect remains completely unaffected, only a K28 was found to be achievable.

Team Sustainability, Energy & Comfort (6)

Emma 569 A0561 Gemiddeld

ir. arch. Emma Van De Steene

Energy and sustainability advisor
E-mail |
Kopie van Paulus

ir. Jente De Schepper

Sustainability consultant
E-mail |
Jona 569 A6702 Large

ir. arch. Jona Van Steenkiste

Energy and sustainability advisor
EPB reporter
E-mail |
Katrien 569 A0552 Gemiddeld

ir. arch. Katrien Van Lierop

Energie- en duurzaamheidsadviseur
E-mail |
B B Martijn Vyncke 8087 Large

ing. Martijn Vyncke

Daglicht expert
Adviseur technische installaties
E-mail |
BB Robbe oct2014

ir. arch. Robbe Verelst

Energie- en duurzaamheidsadviseur
Ingenieur bouwfysica
E-mail |
TAGS: Daylight| Façade| Feasibility study