An ambitious experiment towards an affordable energy bill for social tenants in the Flemish region of Belgium


In 2018 the Social Housing Company Mijn Huis (My Home) decided to renovate the 30 apartments in Ettingen (Oostrozebeke), Belgium – West Flanders. The two buildings of this social housing project were constructed in 1982. At that time energetic ambitions were practically inexistent which resulted in thermal bridges with mold as a consequence and leaking roofs causing the buildings to degenerate quickly. Many apartments didn’t find new tenants and therefore stayed unoccupied. An optimal solution was required but not so easy to manage. The first question that had to be asked was whether Mijn Huis would demolish and replace the apartments or renovate them. The second question was how to move the tenants to other houses or apartments without the availability to move them all at once. At that time and even at this moment the social housing company doesn’t have enough available dwellings to give the tenants an adequate alternative accommodation.

View of the buildings at Oostrozebeke

At the same moment, Knauf Energy Solutions was in contact with Mijn Huis as well as multiple other social housing companies in Flanders. As a sister company of an important manufacturer of insulation products (Knauf Insulation), their goal was to be able to verify whether the insulation products were installed correctly, by measuring real performance before and after an energetical renovation. With this, they would be able to provide asset owners with advice on future renovations based on actual measured data.

In 2019 Knauf Energy Solutions met several members of the European Parliament to propose their vision on the European energy market by introducing “Building the World’s Virtual Energy Infrastructure” by realising 400.000 smart retrofit homes that equal the equivalent profit of 1 Gigawatt power station. Mijn Huis also participated in this meeting.

In 2019 Knauf Energy Solutions won the tender as an energetical advisor for the renovation of the 36 apartments in Oostrozebeke. For the design of the architectural and technical part architect Sileghem & Partners, located in Zwevegem, was selected. Further realisation will be fulfilled within the possibilities of the European tendering legislation.

The first ambition of Mijn Huis was to find out what the real energetical improvement would be according to the investments necessary to refurbish the building. In the past, no one had an idea whether the investments made were profitable or not. Even worse is the experience that some investments were just money wasted or that the renovation efforts, later on, appeared to be useless.

Therefore, it was important for Mijn Huis to start with a zero-measurement in the dwellings situated in Oostrozebeke.  Knauf Energy Solutions was at that time the only partner who could guarantee Mijn Huis an indicator of the energy demand for every household. As a result of a pre-monitoring with a specific sensor kit Knauf Energy Solutions could measure the household heat consumption, an Energy Demand Indicator as well as temperature and humidity levels for each apartment.

After a winter of measuring (2019 – 2020) the first monitoring results were released.

Now the pre-monitoring results are known the creation of the renovation plan could start in deliberation with architects, engineers and other energy specialists based on the actual measured data.

After several meetings, Knauf Energy Solutions proposed several practical solutions for several interior and exterior problems of the building. Wall and roof insulation will be optimized, finding a good balance between cost and performance, and going further than minimal requirements. Thermal bridges will be solved using wall covering insulation at the outside of the buildings and together with the technical engineers, a solution with combined heating must reduce the heating costs and CO2 production for the tenants.

The start of the retrofit is expected in the springtime of 2024. The architects and engineers are working on the blueprints and after the building permit is received, Mijn Huis will start the tendering for the works. During these works, there will be an on-site quality control to guarantee energetical performance.

After the renovation, Knauf Energy Solutions will re-install the monitoring devices and will restart measuring. It is only after thorough evaluation of the results that we can conclude whether some of the investments were worth it or not. In this case however, Mijn Huis is very hopeful.
Former experimental retrofits proved that the efforts in this domain resulted in spectacular improvements. A renovation of 20 homes, constructed in the 1970’s shows an average performance improvement of just over 50%. This retrofit will lead to an average annual saving for the tenants of €780 and this for a long period. For people with a yearly income between €12.000 and €15.000, this means an improvement between 6,5% and 5,2% of the yearly budget that can be used for other basic or necessary purchases.

At the moment the social housing company Mijn Huis already demolished 112 dwellings and rebuilt 156. However, experience shows that this approach is no longer achievable. With the exploding building prices new dwellings are becoming unaffordable and the temporary relocation of the tenants increases the workload for the social housing company’s staff. Furthermore, high relocation costs must be paid by the social housing company itself, and above all the temporary vacancy of dwellings and as a consequence the decrease of available dwellings means that candidates on the shortlist, waiting for a new home, must wait an even longer time before a new home is assigned to them.

Everyone involved in the renovation ambitions of the European and National/Regional Governments is aware of the fact that the demands for energy improvements go beyond the financial possibilities of lots of participants in the social housing sector but also beyond the capacity of the housing industry. The acceleration in the time path and the tightening of the energy labels puts the whole energy approach in a very delicate situation.

This explains the importance of the homework accomplished by the concerned partners. Detailed preparation, monitoring afterward, and honest evaluation of energy improvements against the investment costs are crucial to reach the European ambitions or at least to guarantee that social tenants can afford a good living.

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