Soprema and the CSTB signed a research framework agreement in 2021 on several themes, including adaptation to climate change in a non-air-conditioned building. Testimony from Étienne Crépon, president of the CSTB.

Climate change questions the design of buildings, and in particular our habits in terms of managing summer comfort. In this context, we carried out, in this new building without air conditioning, an experiment on the perception of thermal comfort of office occupants during the summer of 2023, which was a hot summer! The CSTB has deployed the Pulse method, which makes it possible to evaluate a place based on physiological and sensory tests with a panel of users. We analyzed the explicit and implicit perceptions of ten employees and thus demonstrated the adaptation of this building to high heat.

This framework agreement also covers rainwater management. They constitute a resource that is still too poorly exploited. Water can be recovered and stored on the roof to reduce rainfall peaks in the networks, be reused for uses that do not justify potability, and allow a vegetated substrate to be maintained in good water conditions. Although difficult to quantify at this stage, and this subject is part of our research, water storage also allows an attenuation of the temperature rise of the roof surface via the absorption of energy during the phase change of stored water (latent heat of vaporization). The management and recovery of rainwater on roofs therefore constitutes a relevant field of R&D for our collaboration, and on this theme we have already initiated two projects:

-Doctoral research on rainwater management towards an understanding of the ecosystem services of nature-based solutions, with a particular focus on green roof terraces.

-Alternative management of gray water in collaboration with the Water, Environment and Urban Systems Laboratory (Leesu) and the Aquatiris design office, on phytopurification processes for gray water on green roof terraces. A pilot is also installed on the roof of the Grand Charles, the Strasbourg headquarters of Soprema.

The principle of free-cooling according to the project architect

Free-cooling is based on the use of natural cooling sources such as cold outside air, to regulate the temperature inside a building. Explanations from Alexandre Grenier, the architect in charge of the project.

Operation

Intelligent ventilation systems: free-cooling systems are designed to use outdoor air when it is cooler than indoor air. Instead of running air conditioning units, a ventilation system is programmed to introduce outside air directly into the space to be cooled. We also call it night-cooling, because this system is generally used at night when temperatures are cooler and when premises are unoccupied.

Heat exchangers: Heat exchangers are used to transfer coolness from outdoor air to indoor air. On the front, the heat exchanger is a grille on the exterior side and a panel, either glass or solid, on the interior side, which opens by the action of a cylinder. On the roof, we have skylights and a large vault (Bluevoûte) developed by the company Bluetek.

Automatic control: the free-cooling system is equipped with temperature and humidity sensors that monitor outdoor and indoor conditions. These sensors allow the system to automatically decide the optimal time to use free-cooling (open the lower ventilation grilles, the skylights and the roof at the same time), depending on weather conditions and cooling needs.

Additionally, a fireplace effect is created. Fresh air enters through the facade grilles in the lower part, and the hot air which rises naturally is evacuated through the skylights and the vault. The advantages of free-cooling are mainly linked to energy saving and the reduction of operating costs of air conditioning systems. By using outside air to cool buildings when outdoor temperatures are favorable, businesses and organizations can reduce their reliance on air conditioning systems running at full capacity, resulting in significant energy savings. In summary, free-cooling is a smart strategy to reduce air conditioning energy consumption by exploiting the natural resources available for cooling, which is beneficial both economically and environmentally.

Laboratory work at Soprema

The laboratory tests the entire life cycle of the brand's polyurethane foam insulation products, from the transformation of raw materials to the fate of waste, including the performance of the insulation over fifty years.

-So-called “curving under thermal gradient” tests – the Technicum – make it possible to verify that the flatness of the panels remains consistent when their two faces are at different temperatures. This configuration is found particularly in the case of flat roofs.

- Dry ovens allow samples to be stored at 70°C for one hundred and seventy-five days, in order to achieve accelerated aging of the polyurethane foam insulating panels according to the EN 13165 standard. This accelerated aging makes it possible to guarantee thermal performance at twenty- five years. Wet ovens allow samples to be subjected to different temperature and humidity conditions, in order to determine their dimensional stability according to the EN 1604 standard and the CSTB guides.

-The Méca Dynamique laboratory has several two-column testing machines for carrying out traction and compression, peeling and bending tests according to standards EN 826 and EN 1607. This equipment makes it possible to control the mechanical performance of the products, including the compressive stress at 2% and 10% and the tensile strength perpendicular to the faces.

-The Analytical laboratory allows the viscosity of raw materials to be measured at different temperatures between – 20°C and + 300°C using a viscosimeter.

-The Chemistry laboratory allows you to work on the use of new raw materials. Mechanical agitators offer the possibility of carrying out foaming and thus characterizing polyurethane foam formulations, predicting their hardness, the speed of expansion, the evolution of temperature, pressure and polymerization.

-The Méca Statique laboratory evaluates the response of insulation materials subjected to vertical stresses (for example under a slab) over long periods of time.

-The scanning electron microscope allows detailed observation of the structure of the foams. The equipment is equipped with an X-ray emission analysis module giving access to the nature of the atoms making up the material.

-The Lambdameter laboratory allows you to know the thermal resistance R and the thermal conductivity (lambda).

-The fire laboratory has a fire cabin to determine the ignitability of insulators.

-Water absorption by cellular insulation products is also determined. A dynamic stiffness test bench allows the evaluation of the consistency of acoustic performance, an essential characteristic of products used in ground applications.

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