ACS and the quality of our homes: La Rochelle University studies on building envelopes

The Laboratory of Engineering Sciences for the Environment (LaSIE UMR CNRS 7356) at the University of La Rochelle is a Research unit dedicated to the themes of heat and mass transfer in materials and envelopes. LaSIE thus brings together a wide range of expertise in the field of environmental engineering (mathematics, physics, civil engineering, chemistry and mechanics), interested not only in the durability and performance of materials subject to environmental constraints but also in improving comfort and indoor air quality in living spaces.

The building envelope represents the interface between the external environment subject to meteorological hazards and the internal environment. This hitherto passive envelope is evolving into a more complex object, integrating new functionalities and materials. Building envelopes are thus becoming more complex elements whose characteristics can change throughout the day and/or year. It is necessary to quantify the contributions of these new multifunctional walls and assess their impact on hygrothermal comfort and building performance. The ETHER (Evaluation THermohydriques des Enveloppes par boîte chaude gaRdée) platform fits into this approach, offering an experimental tool to assess the performance of building envelopes in a controlled environment, both for construction and renovation of buildings. This platform is open to the scientific community and shared with the Tipee company (Technology platform for sustainable construction).

For this purpose, the LaSIE laboratory has equipped itself with one of the products in the ACS climatic chamber range, the calorimeter for thermal transmittance tests. This is a calibrated double chamber for characterising the thermal and water performance of the envelope components and can accommodate wall samples measuring 2.2 × 2.2 m and up to 45 cm thick. Temperature (-20°C to 45°C), humidity (5% to 95%) and pressure (0 to 40 Pa) conditions can be imposed on both sides of the samples. Two configurations are provided: protected hot chamber operation (temperature control) and dual chamber operation (temperature, humidity and/or pressure control).

The calibrated dual chamber is a reliable instrument that can be adapted to a wide variety of conditions. Under static conditions, tests can be carried out quickly, repeatably and with high accuracy thanks to appropriate metrology.

The advantage of the ACS chamber lies in its ability to independently control the three important heat transfer variables of temperature, humidity and pressure. Finally, dynamic conditions characteristic of real environments can be reproduced to allow better estimation of in-situ wall performance.

La Rochelle also chose our chamber for its advanced test management and technical implementation solutions that enable a wide range of measurements.

This has allowed the University to dedicate the calorimeter to three types of activities:

• research projects in collaboration with the LaSIE laboratory dealing with hygrothermal transfer issues
• tests as part of services to support the development of innovative products for the envelope
• projects intended for institutional structures for the purpose of control or expert opinion on works.

Controlling the pressure between the two chambers also provides an additional benefit: observing the influence of this parameter on hygrothermal transfers and better assessing the influence of permeability on the envelope performance.

"The ACS calorimeter is a high quality piece of equipment, which allows precise control of the two chambers and obtains repeatable measurements. In addition, it is possible to integrate specific metrology for each test in order to meet the needs of research projects. Finally, the proximity of ACS France's local staff ensures a reasonable response time in the event of a malfunction."