Hygroscopic properties are an essential topic in the construction industry, particularly for projects aimed at optimizing building comfort and sustainability. But what does this property actually mean? How does it work for building materials? What advantages does it offer for buildings?
What is a hygroscopic material?
According to Larousse, a hygroscopic property is the ability of a material to absorb and retain moisture from the ambient air. This characteristic depends on various factors, such as the molecular structure of the material and environmental conditions (temperature, relative humidity, etc.).
For building materials, this property can directly influence indoor air quality, thermal comfort, and even the longevity of structures. Common examples of hygroscopic materials include bio-based materials such as wood and cellulose insulation, as well as certain types of plaster.
How does a hygroscopic material work?
Hygroscopicity works through the interaction between water molecules in the air and the pores or surfaces of the material. A hygroscopic material acts as a natural humidity regulator: it absorbs excess water from the air in humid conditions and releases this moisture when the air becomes drier.
Take wood, for example: its cellular fibers contain compounds capable of retaining water molecules. This process of absorption and desorption helps stabilize relative humidity inside buildings.
What are the advantages of hygroscopic materials in construction?
1. Natural humidity control
Natural humidity regulation is one of the main advantages of hygroscopic materials. These act like "smart sponges," absorbing excess moisture from the ambient air when it is saturated and then releasing it when the air becomes too dry. This mechanism helps maintain stable relative humidity, ideal for human comfort (between 40% and 60%). This helps prevent problems associated with an atmosphere that is too humid, such as mold growth and odors, or too dry, such as respiratory irritation.
In short, hygroscopic material promotes a healthy and comfortable indoor environment.
2. Thermal comfort
Hygroscopic materials contribute to thermal comfort by regulating not only humidity but also the temperature of interior spaces. When a material absorbs moisture from the air, it releases a small amount of heat (exothermic phenomenon), and conversely, during desorption, it absorbs heat (endothermic phenomenon). This dual mechanism acts as a thermal buffer, mitigating temperature variations. For example, a wood-frame building provides a cooler feel in summer and a warmer feel in winter.
This ability to stabilize the indoor microclimate improves occupant comfort while reducing heating and cooling requirements.
3. Increased durability of structures
Hygroscopic materials contribute to the durability of structures by regulating humidity variations. By absorbing excess water in the air and releasing it when the air becomes dry, they limit condensation, swelling, and shrinkage, which can weaken building materials. This reduces the risk of cracks, deformations, and damage caused by water cycles. For example, a material such as wood, when used under controlled conditions, offers increased resistance to climatic fluctuations.
By stabilizing the internal humidity of structures, hygroscopic materials extend their lifespan and minimize maintenance requirements.
4. Positive environmental impact
Among hygroscopic materials, bio-based materials such as hemp and cellulose insulation cellulose insulation, stand out for their low environmental impact. Derived from renewable resources, these materials require little energy to manufacture, thereby reducing their carbon footprint. Their ability to absorb and release moisture from the air naturally improves indoor comfort, limiting the use of energy-intensive systems such as air conditioning or mechanical ventilation.
By opting for hygroscopic bio-based materials such as wood and cellulose insulation, construction projects are part of a sustainable approach, reducing not only energy consumption but also the building's overall carbon footprint throughout its life cycle.
What are the differences compared to conventional materials?
On the other hand, non-hygroscopic materials, such as mineral insulation, do not interact with ambient humidity. For example, in use, hygroscopic materials, such as cellulose insulation, and conventional materials, such as mineral wool, offer very different experiences in terms of comfort and performance. Hygroscopic bio-based insulation actively regulates indoor humidity by absorbing excess water in the air and releasing it when the air becomes drier. This property limits the risk of condensation and mold, creating a healthier indoor environment. Mineral insulation, on the other hand, does not participate in this regulation, which can lead to areas of condensation if humidity is not properly managed.
Hygroscopic properties play a crucial role in the performance of building materials. They offer advantages in terms of comfort, durability, and environmental impact. Choosing to incorporate hygroscopic materials, such as wood or cellulose insulation, into construction projects can be a natural and effective solution for improving the quality of built spaces. For more information, please consult sources such as CSTB or ADEME, which offer in-depth studies on environmentally friendly and high-performance materials.
