Hem district

Building Characteristics



Construction year


Ground floor area

84 m² per house

Building Owner

Vilogia (Social housing association)

Building Manager


Refurbishment package

Prefabricated façade with integrated heat pump and PV panels or solar thermal collector>

This package includes:

  • a prefabricated timber façade
  • a heat pump for centralised heating
  • photovoltaic panels or solar thermal collectors

Prefabricated timber framed façade elements are used for the external thermal insulation of walls. The prefabrication enables the industrialisation of the manufacturing process, and reduce the duration of on-site works. The system also integrates windows and HVAC devices. In this refurbishment package, the prefabricated façade is combined with a heat pump that provides space heating and domestic hot water, and with a ventilation with heat recovery.

Photovolaic panels or solar thermal collector are also installed on the roof.

Performance Before

301 kWh /m² (primary energy)

Performance After

76 kWh /m² (primary energy)


Energiesprong is a new refurbishment standard originated in the Netherlands to massify high-performance energy refurbishments, starting with the social housing stock. The principle: long term guaranteed net zero energy and high quality and comfort refurbishment (up to 30 years), with a minimum disruption for tenants thanks to the off-site construction of large components, and an overtinvesment being financed by the money saved on energy bills and maintenance.

Highly insulated walls, roofs with integrated solar panels and other large components are made off-site, which allows whole-house retrofits to be done quickly and with minimum disruption to tenants. Real-life performance for energy use and indoor comfort is guaranteed for up to 30 years.

Within the E=0 project, funded by Interreg North-West Europe, Vilogia, a social housing association, tested the EnergieSprong approach for the first time in France on 10 individual houses in Hem (59) to demonstrate the replicability of the project. These houses are typical northern brick houses with two floors and four rooms built in 1952, with an initial energy performance of E. This first French refurbishment comes with a 25-years performance warranty on the energy performance.

The retrofit was non-intrusive (pre-fabricated facades, new roof with solar panels, new installations e.g. floor and heating plant), esthetic and completed within six weeks, and without the resident needing to move out. Moreover, tenants also enjoy new refurbished kitchen and bathroom, and will have access to a monitoring device and coaching to master their energy consumption.

List of stakeholders

Activity : Social housing association
Organization : Social housing association
Rabot Dutilleul Construction
Activity : Buildings design and construction company
Organization : Buildings design and construction company
Activity : Design and installation of energy solutions
Organization : Design and installation of energy solutions
Activity : Engineering Company
Organization : Engineering Company
Smart Module Concept
Activity : Design, fabrication and installation of prefabricated modules
Organization : Design, fabrication and installation of prefabricated modules
Redcat Architecture
Activity : Architects
Organization : Architects
Activity : Engineering Company
Organization : Engineering Company

Local climate, constraints, regulations and incentives


Hem (59 - France), rue Védrines 38-56


  • Climate: Western
  • Heating Degree Days: 2518,4 (2017)
  • Local constraints: Respect the local architectural chart (northern brick house)


Site after refurbishment ©Vilogia

Lessons learnt and guidelines for replication

Lessons learnt

Design vs construction phase

The first year of the project was about learning and sharing project between the Netherlands and France.

The design phase was crucial, occupying 80% of the project. It was therefore a mode of operation that was atypical, requiring adaptation and modification of the way of working. Indeed, due to the short deliverable, everything must be anticipated, sequenced, imagined, programmed in advance. This is essential to manage the technical part and the tenant management part.

Construction time has been at least twice as short as usual thanks to the pre-industrialized process, but in the long term, construction site delays are expected to be further reduced by 6 to 3 weeks.

Collaboration takes on a different meaning

The actors had to be agile, flexible, cooperate andcommunicate one with others to make processes more fluid and contribute to success. Indeed, EnergieSprong is an inovativeproject because it requires co-construction with the whole group. A cross-functionnality of the team is a key to success that allows skills development of each actor involved in the project.

Site after refurbishment ©Vilogia

In addition, the approach starts with the landlord, who is the one who drives the approach and the demand. Establishment of the terms of cooperation between landlords, industries, project managers, engineers, architects should be set in the early stage of the project.

A 25-years performance warranty was obtained and could be revised according to new regulations. Moroever, project monitoring meetings are planned on a yearly basis.


Tenants satisfaction

Vilogia had to define the objectives of the project (zero energy over the year and tenant satisfaction), and make sure that the group was responding well to this demand.

An importance to the support of tenants must be given. They must be involved because the success of the project depends on reasonable usage behaviours. A dedicated contact person is needed for training in new equipment and support in monitoring consumption.

Things must be kept simple.

In addition, since the tenant was involved in the renovation of his dwelling, it was necessary to be responsive to his needs.

After renovation, the tenants reported an excellent indoor comfort with a good external sound insulation and no more air leaks. The dual flow ventilation was also very appreciated since a uniform heating was noticed during winter and a  cooler house in heatwave periods. This indoor confort and sense of well-being facilitate the behaviour change and the eco-gestures integration.

Moreover, tenants enjoy new refurbished bathroom and kitchen. This last one should be pre-industrialized in further refurbishment projects.


Massification of the demand

If the price of these energy renovations is already falling, the economic equilibrium will only be achieved with a mass demand movement. Through a scale effect, the massification of demand around a single set of specifications is a leverage that will allow solution providers to industrialize their production processes and implement a cost reduction. The long-term objective: the pre-industrialisation of 95% of the renovation work!

It would make a lot of sense to continue to support the start-up of the sector through decreasing subsidies towards pilot projects in each French region. It took nearly 1000 in 5 years in the Netherlands to reduce costs by 50%.


No specific recommendations for this case study

Useful Links

Energiesprong website
Detailed description of the case study
Vilogia website