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SERR'URE: the specificities of this new Walloon low-energy urban greenhouse

On 20 December 2022, the SERR'URE was inaugurated in Gembloux, on the ULiège campus. SERR'URE is a low energy urban greenhouse. It is one of the four pilot projects developed within the framework of GROOF ("Greenhouses to Reduce CO2 on RooFs"), a European project which aims to facilitate the emergence of rooftop greenhouses in our territories and in which the Smart City Institute (SCI) has been a partner since 2017. Indeed, the challenges to which the development of rooftop greenhouses responds are in direct line with those of sustainable and smart territories that SCI is studying.

But what are the specificities of this Walloon rooftop greenhouse? Why is SERR'URE so innovative and what is the advantage of this type of greenhouse for our cities ? In this article, our team invites you to dive into the heart of the project, with our colleagues Florent Scattareggia and Nicolas Ancion, stakeholders of the GROOF project who have followed the evolution of the greenhouse since its inception.

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Roof greenhouses for cities: what are the advantages?

As we explained in a previous article, "a sustainable and smart city is also a city/territory that thinks about a sustainable and smart production and commercialisation of the food we are consuming." It is in this logic that urban agriculture is now gradually making its place, and rooftop greenhouses have been emerging in the urban landscape for a few years. The advantages and possibilities offered by rooftop greenhouses for a city are indeed multiple. 

Firstly, they allow, by their location, to optimise space (which urban areas can often lack) since most urban roofs remain generally unused. 

In terms of well-being and social cohesion, this type of installation allows citizens to reconnect with nature and, possibly, with each other through collective activities. 

Furthermore, the development of certain synergies (between the building and the greenhouse on its roof) can contribute to a better management of the necessary resources. Indeed, if it is well integrated into the existing building, the greenhouse allows considerable energy savings (in terms of heating in particular) since it can recover the stale air from the building's heating system. Indeed, this air, which is usually directly evacuated from the building, is reused to heat the greenhouse. Enriched with CO2, this air is used - and at the same time purified - by the plants present in the greenhouse, by photosynthetic process, for their growth and metabolism. It is therefore a winning solution at several levels.

Greenhouses such as Symbiose in Nantes (one of the 20 greenhouse projects supported by GROOF) even go further, since they also serve to heat the building's water, taking advantage of the sun's effect to heat the water tank inside. Finally, rainwater can also be collected and used by the greenhouse.

iconeInfo  The GROOF project aims to study these possible synergies between buildings and greenhouses, as well as the technical, administrative and financial barriers that may arise in this context. 
 Read more :

> Starting a rooftop greenhouse project : the good questions to ask 
Bankruptcy of Urban Farmers – What are the lessons to be learned ? (GROOF case study) 

The specificities of SERR'URE

In theory, then, rooftop greenhouses are attractive; but what about the SERR'URE itself? 

4 years to emerge from the ground  

SERR'URE is a long-term project: "it will have taken us 4 years to see this project really come to fruition, with the launch of the first cultures at the beginning of 2022" explains Florent.  Indeed, because of its innovative and unprecedented nature in Wallonia, 3 years will have been necessary (between 2018 and 2021) to be able to shape the project and unlock many administrative barriers. "We found ourselves in a sort of legal void, which created several blockages and lengthened the deadlines when the authorities had to grant us authorisations" adds Florent. "Not to mention Covid, who passed by. However, once the project was validated, the construction of SERR'URE was very quick: in 6 months, it was there, ready to receive our first plants" (end of 2021).

How was SERR'URE designed?

In terms of conception, SERR'URE has several specific features:

A roof with an intact waterproofing

SERR'URE is located on the roof of the TERRA research centre, which houses laboratories reproducing extremely precise growing conditions. It was therefore necessary to ensure that the construction of the greenhouse did not degrade the waterproofing of the roof, to avoid any interference that might have compromised the experiments carried out on the floor below. For these reasons, it was decided not to touch the waterproofing of the roof and to opt for concrete ballast rather than fixings directly anchored in the roof. If necessary, SERR'URE could be removed and recycled without damaging the rest of the building.

An increasingly energy-efficient greenhouse

The greenhouse has also been designed to be very energy efficient. For example, simulations carried out beforehand permitted the selection of its optimal half-chapel shape (see photo), which in this case allows for energy savings of 13% compared to a "classic" chapel greenhouse.  In the coming months, two other solutions will contribute to its energy efficiency: firstly, the connection to the lost heating flows of the TERRA building, and secondly, the installation of very specific photovoltaic panels: "these will be prototypes that will be installed not on the roof of the greenhouse (which would interfere with the growth of the plants) but on the interior walls of the greenhouse. Their white colour will also reverberate the light to support the growth of the plants" explains Nicolas.

Serrure-001 Unknown-10


A high-tech monitoring system 

Not only because of its nature as a "pilot project", but also because it is integrated into the ULiège Faculty of Agronomy and the Wasabi* platform, SERR'URE is of course intended to stimulate innovation through research, particularly in bioponics**. "It was therefore important for our greenhouse to be equipped with a high-performance monitoring system so that we could understand which factors could cause problems or favour our cultures" explains Nicolas. The greenhouse is equipped with several weather stations and a whole series of sensors that measure the level of hydrometry, temperature, wind, pressure, CO2 levels, or even the luminosity inside and outside the greenhouse, and which also automatically influence the opening of blinds or windows, in order to benefit from optimal growing conditions. "All the hydroponic tables also have their own monitoring system, so everything is managed automatically: pH management, water level, etc." say the two project leaders.

Finally, what about the budget for designing this greenhouse? The total investment is €480,000. As it is intended for research, it was important that the greenhouse could guarantee a maximum controllable environment, which explains the higher investment (2400€/m²) than in a commercial setting. 

WASABI is the WAlloon platform for Innovative Systems in Urban Agriculture and Biodiversity. It is also a teaching and research platform for urban agriculture and urban and peri-urban biodiversity.
** Bioponics is a practice derived from hydroponics and consists of growing plants above ground using an organic and biological nutrient solution.


SERR'URE, a field of experimentation at different levels

"Throughout the design of the SERR'URE project, we were really moving forward in uncharted territory," says Florent. "As this type of project is completely new to us, we were faced with a series of challenges and we lacked examples - European and local - from which we could draw inspiration. Even though urban agriculture projects were already well underway in Belgium, it was quite a different story when it came to rooftop greenhouses. However, we were inspired by a project in Brussels: BIGH Farm, one of the very first rooftop greenhouse projects developed in Europe."

Convincing and raising the awareness of the Walloon actors involved

Lack of knowledge of this type of project, legal uncertainty, difficulty in making decisions which leads to long delays in response from the authorities, unsuitable market... There can be many difficulties when undertaking an innovative project such as SERR'URE. "The aim of our approach is also to open the way and to raise awareness among all the stakeholders concerned or involved in all the phases of such a project. Whether it be regulators or administrations, who do not always have the appropriate procedures, stakeholders in the project who must be convinced beforehand of its added value in order to be able to carry out the project, or service providers, who must adapt their offer to innovative demands" explain the two project managers.

"During the 4 years we have spent on this project, we have learned a lot. As with the 4 other pilot projects, the analysis of SERR'URE is very enriching because it allows us to feed a best practice guide. We hope that SERR'URE will play its role as a precursor and model at Walloon level, but also more widely at European level."

What are the perspectives for SERR'URE?

All the research conducted by GROOF will enable the greenhouse, and more generally the Wasabi platform anchored on the Gembloux university site, to continue its mission: to explore the agriculture of tomorrow. In addition to biopony and the cultivation of plants with high ecological potential such as hemp, agrivoltaics will also be highlighted with trials of solar panels adapted to agriculture. 

Plateforme WASABI - Bloc-accueil Serrure - Tables bioponie - Bloc accueil


Already in a test phase for 1 year, SERR'URE will not only continue to fulfil the role of a demonstration greenhouse for the public, but will also allow us to continue to study the energy optimisation avenues that it induces as well as its impact and economic viability.

About GROOF 

GROOF, launched in 2017, is a project supported by INTERREG NorthWest Europe that gathers 14 partners (the University of Liège being represented by the Smart City Institute and the CRAU). Each of them is involved in a specific field: agronomy, economic viability and management (an angle dealt with by the Smart City Institute), construction, social and of course energy. The project includes four pilots (in France, Germany, Luxembourg and the Serr'ure in Gembloux, Belgium) which are being studied and monitored scrupulously in order to propose results by the end of March 2023. GROOF also includes a coaching component. A total of 20 European projects will have been supported, including the Symbiose (Nantes) and Green Nest (Brussels) projects.

Thus, the expertise and data collected throughout the GROOF project have been used to draw up a best practice guide for the development of viable and functional models. The objective is to make the design of rooftop greenhouses accessible to all. It will allow any project leader, administration, architect or any other actor interested in this type of project to receive the necessary information. 


After 6 years of existence, the GROOF project is now coming to an end. The closing ceremony, which will include the disclosure of the results, will take place on 25 April 2023 in Bettembourg (Luxembourg), on the site of the IFSB pilot project.


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