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Paint it Green: energy efficient retrofit in Limette, Belgium

Highlighted Case July 2017
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The renovation project "Paint it Green" was undertaken by the owner company CoRI - Coating Research Institute after identifying two important concepts: the need for more space as well as the modernization of the company image. Focusing on these issues, the objective established was to create a building designed in an intelligent and thoughtful way combined with the aspects of being high-tech and durable.


In the collective mind, a "sustainable" building is perceived as a building constructed from natural materials with traditional techniques (timber frame, coated lime or clay, ...). Conversely, when talking about a high-tech building, the company imagined rather large windows, clean lines and advanced technology, or even a "smart" building. Throughout the project, the aim to change these prejudices and design a building which was both environmentally friendly and at the forefront of today's technologies was kept in mind. To achieve this, the principle was to put technology at the service of ecology. Thus, when designing the project, several studies identified the optimal solutions: Dynamic Simulation, PEB (performance énergétique et climat intérieur des bâtiments) study of natural and artificial lighting study, study of solar masks, blower-door, analysis of the life cycle, etc. . Moreover, during the life of the building, users and visitors can be informed and made aware of sustainable development by such examples as; a screen that provides real-time information (consumption, temperature, ...), visible natural materials, dry basin green roof, etc.


In conclusion, the new building has been renovated with smart building applications which integrates advanced technologies in building management and renewable energy production.



Avenue Pierre Holoffe 21, 1342 Limelette, Ottignies-Louvain-la-Neuve, Belgium


Project team

Project management, contractor and owner: CoRI – Coatings Research Institute

Architect design: Helium3

Thermal engineering: Collignon Eng.

Sustainability consultancy: Arcadis

Construction works: Synergie Bois

Interior design: Apruzzese

Electricity works: Lamelec

Certification and monitoring works: MATRIciel

Risk prevention: Pierre Beguin


Time Schedule


Built: 1957

Renovation design: 2013

Renovation works: 2015-2016


Building use and area


The original building consisted of both offices and laboratories. This existing structure has been conserved and now houses the laboratories while the new extension mainly accommodates the offices and meeting rooms. The existing building is brick masonry. The floors and the flat roof are reinforced concrete. Insulation was installed on the exterior walls.

The existing main entrance was decommissioned and relocated to the new part of the building which connects it to the conserved part in the middle of the two buildings.

The built extension was constructed with a wooden frame. The inner load-bearing walls are brick masonry. The non-load-bearing partitions are lightweight, which will facilitate the development of future extensions.


Plot area: 10,854 m2

Green space: 8400 m2

Total Usable Floor Area: 1,444 m2



Renovation costs


Total renovation cost: 1.8 M €

Renewable energy systems cost: 80,000 €

Cost of studies: 250,000 €

Subsidies: 141,700 €


Envelope performance


The existing building was insulated from the outside. This makes it possible to maintain its thermal inertia and to avoid thermal bridges. In addition, this method allows for the risk of interstitial condensation to be easily eliminated.


The exterior envelope of the building extension was constructed with a wood frame structure. This technique makes it possible to place a substantial thickness of insulating material without the walls being too thick. The management of thermal bridges is also facilitated by the use of wood which, although not an insulating material, nevertheless has a coefficient of thermal conductivity λ much lower than that of most other structural materials (brick, concrete, steel , ...). The disadvantage of this technique is the low thermal inertia of these walls, which does not facilitate the control of overheating. The internal walls and screeds are partially made of heavy materials, which do, however, increases the thermal inertia.


The U-Values have been calculated with the official software PEB (performance énergétique et climat intérieur des bâtiments) in detail.


Whole building (0,40 W/m2.K)


Extension (0.29 W/m2.K):

-Wall façade (0.17 W/m2.K ): Timber frame with 22 cm of insulation - blown in cellulose and 5 cm of wood fiber.

- Ground Floor: Floor slab insulated with 12 cm of sprayed PUR and slab finishing polished concrete. The floor above is insulated by 12 cm of projected polyurethane foam (PUR). The insulation is laid on a reinforced concrete floor slab. It is covered by reinforced concrete screed.

- Flat roof (0.14 W/m2.K):  waterproof wood insulated with 16 cm of rock wool. The roof is called a compact roof. This is a flat roof, the insulation of which is placed inside the wooden support with no air gap between the different layers. An airtight vapor barrier should be placed under the bracket. This is not a cold roof because there is no space between the insulation and the sealing membrane.

- Windows: Double glazing (Ug = 1.0 W/m2.K) and aluminum chassis (Uw = 1.13 W/m2.K). The glazing has a solar factor g = 0.53, except for those oriented to the south which have a solar factor g = 0.28 so as to reduce solar inputs and thus reduce overheating during the hot season. The frames are placed in the thickness of the framework so as to create a continuity between the insulation of the facade and the thermal break in the chassis.


Existing building (0.5 W / m2.K):

-Wall façade (0.22 W/m2.K): Isolated from the outside with 10 cm of PIR or projected PUR. The side façades are flat while the front and rear façades have protruding columns. These columns are hidden by new cladding hung on a wooden frame. Polyisocyanurate foam thermal insulation (PIR) is bonded directly to existing parts (masonry and concrete columns).

- Ground floor: Insulated at the bottom with 10 cm of projected PUR. Part of the building above is a crawl space. The floor above this crawl space was insulated from underneath.

On the contrary, the floors and walls were not insulated. This work would be very costly because the secondary premises of the basement did not need to be renovated. In addition, the thickness of the floor that the heat must pass through to the outside air greatly limits thermal loss. Additional note:  the thermal resistance of a layer of material depends not only on its thermal conductivity coefficient λ but also on its thickness, which in the case of the soil is high.

- Basement floor and buried façade: Slab on non-insulated floor.

- Flat roof (0.21 W/m2.K): insulated exterior using 16 cm of rock wool. The existing roof has been conserved and insulated from above (warm roof). The existing waterproofing has been maintained in place and acts as a vapor barrier. To avoid thermal bridges at the facade-roof junction, the acroteres were packed with insulation.

- Windows: aluminum frame and double glazing not replaced existing (Ug = 1.1 W/m2.K). In order to limit the thermal bridge at the facade-window junction, the insulation creates a baffle on the existing chassis. The frames are flush with the brick facing, which makes it very simple to install the batt insulation. The constructive node is not, however, compliant because of the thermal break of the chassis not being in contact with the insulation.


Other details:

Air Tightness Value: 2,31

Building Compactness Coefficient: 0,43

Indicator: DIN EN 13829 - q50 » (en m3/h.m3) (I4) m3/H.m2 n50 (Vol/H) Q4


Energy consumption


Primary energy need : 35,00 kWhep/m2.a

Primary energy need for standard building : 163,00 kWhep/m2.year

Calculation method : RT 2012

Final Energy : 62,00 kWhef/m2.year

Initial consumption : 467,00 kWhep/m2.year


All building consumption is electric (heating, hot water, lighting, ventilation, ...). The final energy consumption is 62 kWh/m²year,  considering 0.29 kg of CO2 per kWh of electricity.

Breakdown for energy consumption:

- Heating: 52,319 MJ/year according PEB

- Cooling: 0 MJ/year (dynamic simulation: no need for cooling)

- Ventilation: 7.006 MJ/year according PEB - ECS: neglected

- Lighting: 23,666 MJ/year (according PEB)

- Electricity another: 110,278 kWh/year (estimated from average consumption before work)

- photovoltaic production: 43,000 kWh/year


GHG in use : 18,00 KgCO2/m2/year


Energy systems


Heating and DHW system: Reversible heat pump with high efficiency air source for outdoor installation and high temperature water


Space heating is provided by an aerothermal heat pump (AWR-HT COP 3.32). This feeds a heated floor in the extension and a forced air heating in the existing building. Pump aerothermal heat of a heating power of 71 kilowatts is placed on the roof of the existing building. In the extension, the heat pump supplies the heating circuit with the ground. In the existing building, it feeds two batteries with preheated ventilation air. Because the heat pump is reversible, it can also be used to cool the building in summer. However, this function was installed as a security and should not have to be used according to the building design.

The heat pump is reversible, this system can also cool the building if needed. However, the dynamics simulation showed that the active cooling was not necessary, so this is only a security. The extension and the existing building are ventilated via a double-flow mechanical ventilation system with heat recovery (78% yield). The ventilation unit is equipped with a bypass to avoid overheating in summer. The building can be cooled naturally by opening windows on opposite facades. A small electric heater allows for hot water in the shower and kitchen sink but hot water the building is minimal.


Photovoltaic solar panels on-site

The 196 photovoltaic modules (Ç260Wp) placed in the garden at the rear of the building achieve an output of 50.7 kWp for an estimated annual production of almost 43,000 kWh. The electricity produced will be completely self-consumed. Indeed, many measuring devices present in laboratories operate continuously and require a lot of electric power. The return on investment time is estimated at 6 years.


Smart Building with advanced control and monitoring technologies

All building technologies are managed by the GTC. Some information is transmitted in real time on the screen placed in the building lobby. Thus, occupants and visitors can follow live the evolution of consumption.

Smartgrid: With equipment installed in the building, and primarily the GTC, the building is ready for connection to a Smart Grid. To date, these are not yet available in this region.

Users’ opinion on the Smart Building functions : CoRI: "It is very comfortable not having to think about turning on and off lights in different area. Regarding the setting of the temperature and air exchange, people who are in charge of the system. are very friendly. "

Synco building automation: The Synco 700 is a communicative and flexible pre-programmed controller. The Communication on KNX allows Synco controllers to exchange a lot of information together: temperature, time programs, energy demands, defects etc. This also allows to upload all the information to a supervisor or directly onto the web.

Centralized technical management (CTM) allows to retrieve data from different meters in the building. This falls under energy consumption (lighting, heating, ventilation and hot water are measured separately) but also other consumption (rainwater, mains water) and energy production (via photovoltaic). This data is then communicated to the shapes and the building users and visitors via the screen placed in the building lobby. The GTC also allows users to easily set up the technical facilities where they can change the desired temperature in each room if wanted.


Innovative LED Lighting

Luminaire LED ArimoS: LED luminaire with microprismatic cover CPD. A built-in exposed grid ceiling 60x60 cm module. Applications: offices, corridors, lobbies, meeting rooms, retail areas, waiting rooms, ... System LED luminaire luminous flux 4000 lm, connected load 40 W, luminous efficiency of 100 lm luminaire / W. Color neutral white light color temperature of 4000 K, color rendering index Ra> 80. Parameters of the rated lamp life: L80 rated life: 50000 hours

Besides the aesthetic integration into the false ceiling in mineral slabs, the choice of high performance luminaires also allows to significantly reduce electricity consumption for lighting. They also limit the internal loads and therefore not causing summer overheating. These devices were used to equip every office in the extension and also a part of the laboratory to replace the outdated fixtures.


Charging point for electric car: charging point for electric cars

This terminal, located in the front of a parking space, allows users or visitors of the building that have an electric car to recharge while in the building.


Rainwater harvesting

All of the water falling on the building roof is directed to a tank with a volume of 20 m³ which allows to collect 450 m³ over the year. Rainwater is used to supply the toilets and External tanks (for roadsides). There is, therefore, limited use of drinking water in the kitchen sink, the shower, the sanitary sinks and sinks in a few laboratories. The rainwater tank is sized for 30 days of autonomy for the toilet, so it should cover 100% of this consumption. When the tank overflows, the water is routed to a dry area. This is a depression in the ground for the collection, retention and infiltration of rainwater. This is converted into green space and thus integrated into the landscape. It prevents any discharge of rainwater into the public sewer. In addition, its location at the entrance of the site allows for visitor and tenant awareness of the use and limitation of rainwater.


Awards and recognition


Winner of Green Building Solutions Awards 2016 in the Energy & Temperate Climates category (

One of the winners of the Bâtiments Exemplaires Wallonie 2013 contest (


Additional information


Video of the project:

Photo gallery after renovation works:



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