Efficient buildings


How can we use data to help cities accelerate retrofitting and stimulate renovations to make older residential buildings more energy efficient?

Challenge Identifier: BC4 – 2018 – M
Sponsor City: Mechelen

Mechelen is located in the heart of Flanders, between Brussels and Antwerp. This central position ensures that both cities are reachable in 20 minutes. Mechelen is therefore an ideal operation base.  The territory not only hosts the historical city center but also 5 smaller villages: Heffen, Hombeek, Leest, Muizen and Walem. This accumulates in a total of 86.304 inhabitants. The population is very diverse, 27,5% of the population has non-belgian roots (couleur locale, Prisma vzw, 2013). Mechelen has a very active and positive take on diversity.  The central position not only attracts a growing population but also multiple companies. Mechelen has a strong manufacturing, creative and innovative sector.

The city was awarded the “best Belgian local government” award in 2016. This award outlines the performant public services of Mechelen. The city has different transversal red lines, such as climate neutrality, diversity, child-friendliness,…. However, the city believes in a co-creative city and places emphasis on participation as demonstrated by the annual inhabitants meetings and specific participation projects, such as the renovation of the village center of Hombeek. Other city partners are involved in the smart city through “citylabs”.

Mechelen signed the Covenant of Mayors in 2012, committing itself to an emission reduction of 20% by 2020 and an overall commitment to become carbon neutral. A Baseline Emission Inventory (2011) and a Sustainable Energy Action (2013) plan were submitted. This Inventory showed an overall scope 1 and scope 2 emission of 584 kton CO2e.


Although modern buildings are built to energy efficient specifications, the majority of city centre residential buildings were constructed before 1980 and are therefore energy inefficient and in need of deep renovation. This locks local authorities into high carbon-footprint futures even where reductions are made elsewhere. In particular, condominiums or other co-operatively owned residential buildings are an attractive target for such renovation efforts, as significant financial and carbon savings can be made while also benefiting the greatest number of private owners. Further, these condominiums can be used for a basis of the production of green energy, for instance, by the addition of solar panels.

However, this is complicated by factors such as the complexity of financing a condominium renovation project and the long decision-making process to develop a collective renovation project. These combined make the condominium renovation market unattractive to building professionals. Further, the target audience is often hard to reach, often comprising elderly people and lower income groups.

Finally, the return on investment for owner versus tenant is often imbalanced. This is both the case for condominiums and rental houses in general.

Expected Outcomes

  • Measurement tools for energy efficiency not on an individual level but on a shared property, streetlevel, at the level of the neighbourhood/district…;
  • Awareness tools for owners/tenants;
  • Calculation models for impact analysis;
  • Scenario tools for local authorities, builders, tenants and owners;
  • New business models for joint renovation;
  • New business models for joint investment in green energy.

Expected Impacts

  • Average energy efficiency of residential buildings increases;
  • Energy costs for inhabitants decrease;
  • Living quality indoors improves;
  • Green energy production in older residential buildings is increased;
  • Significant contribution to Covenant of Mayors.The EU Covenant of Mayors for Climate & Energy brings together thousands of local governments voluntarily committed to implementing EU climate and energy objectives.


  • District borders
  • Ownership, age of building (kadaster)
  • Electricity & gas use (Eandis)
  • Solar panels (Eandis)
  • Thermographic map
  • Flemish solarmap