Dethy - Belgium

Extension + refurbishment

  • Building Type : Collective housing > 50m
  • Construction Year : 1865
  • Delivery year : 2021
  • Address 1 - street : 3 rue Dethy 1060 BRUXELLES, Belgique
  • Climate zone : [Cfb] Marine Mild Winter, warm summer, no dry season.

  • Net Floor Area : 280 m2
  • Construction/refurbishment cost : 385 090 €
  • Number of Dwelling : 2 Dwelling
  • Cost/m2 : 1375.32 €/m2
  • Primary energy need
    24 kWhep/
    (Calculation method : Other )
Energy consumption
Economical buildingBuilding
< 50A
51 à 90B
91 à 150C
151 à 230D
231 à 330E
331 à 450F
> 450G
Energy-intensive building

The DETHY project consists of an elevation and energy renovation of a single-family house in Saint-Gilles (1060), Belgium, following the principles of the circular economy. It is based on the following 4 pillars:

  1. Eco conception;
  2. Use of BIM and digital tools;
  3. Objective of passive renovation;
  4. Application of circular economy principles.

If you had to do it again?

Synthesis and feedback

One of the initial working hypotheses was that the 4 pillars that support the project work concurrently and bring more than if they were applied in isolation. It can be seen that having tackled these subjects head-on while maintaining rigor in management has made it possible to meet their respective objectives.

A logic to refine

The fairly long duration (2015 - 2021) of the project has allowed many experiments and maturations on how to approach energy renovation with increasingly constrained resources. The end of the project also coincided with the launch of RENOLUTION across the Brussels region. In connection with the objectives of carbon neutrality by 2050, this raises the following question: how to renovate energy in a circular approach 200,000 buildings (or 600,000 housing units)?

The equation is complex because there is obviously a lack of strength and skills at the level of companies and project managers. Not to mention the motivation and budgets of the clients. In this context, the experience of this project allows us to draw the following conclusions:

  • To consider large-scale renovations, one must have an extensive but detailed “building knowledge”.
  • The need for maximum maintenance of the building demonstrates the importance of the inventory.
  • This allows each building to have a starting point for a renovation project.
  • It is necessary to speed up the renovation process, both in terms of studies and their implementation.
  • In this context, digital technology can bring productivity gains.
  • It must nevertheless be used wisely and not generate too many complexities of use while maintaining its effectiveness.
  • Reuse is a flow of atoms that requires rigorous organization and planning

See more details about this project

BIM approach

See the explanations in the attached file in the SOLUTIONS section

Photo credit

Stephanie Roland + BXLMRS



Construction Manager

Type of market

Not applicable

Other type of market


Allocation of works contracts

Separate batches

Energy consumption

  • 24,00 kWhep/
  • Other

    • Heating: 5,957 Kwh/year
    • DHW: 3,421 kWh/year
    • Auxiliary needs (ventilation / lighting / household appliances): 1,058 Kwh/year

  • 560,00 kWhep/

Real final energy consumption

    30,00 kWhef/

Envelope performance

    See the explanations in the attached global file + PHPP

  • 2,21
  • EN 13829 - n50 » (en 1/h-1)

  • 1,80

More information

See the explanations in the attached global file.

Non-renewable primary energy consumption

59,80 kWhep/


    • Individual gas boiler
    • Individual gas boiler
    • No cooling system
    • Double flow heat exchanger
    • Solar photovoltaic
  • 30,00 %
  • 1 single protected volume.
    1 ComfoAirQ 350 DF ventilation with enthalpy exchanger for the living area.
    1 DF ComfoD 300 ventilation for the office part on the ground floor.

    Possibility of extending the surface of the PS from 5 to 11 panels. Planned in the next 3 to 5 years to remove the gas boiler and add an air/water heat pump.

Biodiversity approach

    • Planting a tree (2 if possible) on the plot
    • Greening flat roofs: 15 + 6 + 6 = 27m²

    • Restitution of the open ground on the ground floor courtyard (30m2)


    • Urban heat island

    • Insulation of the entire envelope from the outside except on the street facade
    • U value of walls less than 0.15
    • Increase in the thickness of insulation on the roof (40cm)
    • Use as much as possible of insulation with a high phase shift (wood wool, wood fiber panels)
    • Exterior roller shutter for south-facing roof windows
    • Rolling shutter for the office on the ground floor
    • Installation of "Nimois rattan" on the 6 frames of the south facade

Urban environment

    • Tram station 3 mins walk
    • Metro station 6 mins walk
    • Gare du Midi station (International traffic) 15 minutes on foot
    • 3 car-sharing stations 3/5 minutes away on foot
    • Very commercial district, market several days a week
    • Cultural dynamics: cultural center, galleries, bookstores

  • 110,00 m2
  • 80,00 %
  • 30,00




    Aménagement extérieurs / Déchets : collecte & valorisation

    Use of BIM modeling of an existing building made from a point cloud to identify and quantify FLOW-IN and FLOW-OUT

Construction and exploitation costs

  • 6 000,00
  • 42 670
  • 427 760
  • 69 540

Energy bill

  • 950,00

Circular economy strategy


    • Maximization of the number of impacted batches
    • Maximization of the carbon gain
    • Maximization of the mass of waste avoided

    Objectives not initially set. The project has since been integrated into a study panel within the European FCRBE project. Precise data will be available in the publication of this study in the fall of 2023.

    Integration of the reuse specifically in the special technical specifications of the concerned batches


    Validation of principle at the signature of the contract then by mutual agreement with the companies according to the evolution of the site.


Reuse : same function or different function

    • Structural framework
    • Facades
    • Indoor joineries
    • Floorings
    • Partitions
    • Isulation
    • Suspended ceilings
    • Raised floors
    • Landscaping

    See attached pdf document "reuse summary"

    See attached pdf document "reuse summary"



    • On site, on a dedicated area in a covered location
    • On site, on a dedicated area not covered
    • On site, on a dedicated area in a covered location
    • On site, on a dedicated area not covered
    • No problem of storage, supply correlated to the progress of the works








Environmental assessment

    vertical-align:bottom; white-space:nowrap">363,7941775
    Categories CO2 avoided (kg) Water consumption avoided (m3) Waste avoided (kg)
    Electrical equipment 122.485459 14.22242039 103.3487273
    facades 2994.535 15.62705 5743,358154
    False ceilings 769.6557951 11.97912206 1139.961942
    Big work 368.64 3,288 468.068424
    Insulation 795.0656415 10.53922396
    Interior joinery 166.4 3.73369 281.2294141
    floor coverings 71.34160422 15.23834671 147.1042983
    CO2 avoided (kg) Water consumption avoided (m3) Waste avoided (kg)
    TOTAL 5288.1235 74.62785312 8246,865137

    The reuse operation saved the equivalent of

    • 42,305 kilometers traveled by a small car, i.e. 48 Paris-Nice journeys,
    • 498 rectangular bathtubs filled with water,
    • 16 years of household waste from a Frenchman.


Social economy

Circular design

    • Maximum preservation of existing buildings
    • Maximum densification authorized by town planning = raising one level
    • Creation of an office space on the ground floor

    Intensive use of a library of tools available in Brussels: TOURNEVIE

    See attached PDF with borrowed tools

    • Many exchanges and reuse flows (Flow-in and flow-out)

    See attached PDF

    The following objectives were applied and achieved:

    • Optimized preservation of the building
    • Building densification
    • Raising in wooden structure
    • Use of natural and/or biosourced insulation materials
    • Use of recycled materials in/off site
    • Implementation of PEFC wooden frames
    • Resource conservation

    See pdf Eco-design

    • Insulation of the wooden structure with blown wood wool
    • Exterior insulation in rigid wood fiber panels
    • Interior insulation in flexible wood fiber panels

    See attached PDF

Additional information (PDF documents)

Reasons for participating in the competition(s)

The Dethy project was awarded the BEcircular trophy in Brussels. It is also developing a concurrent strategy with other areas: biosourced materials, eco-design and use of digital tools (Drone, scan, BIM, IFC); to achieve an optimum result in terms of sustainable and virtuous renovation.

Building candidate in the category

Maîtres d'ouvrage privés - bâtiments résidentiels

Maîtres d'ouvrage privés - bâtiments résidentiels

Trophées Bâtiments Circulaires 2023
 BIM wood eco-renovation renewable energies photovoltaic reuse Circular economy

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Author of the page
Lionel Bousquet

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Trophées Bâtiments Circulaires 2023