Exterior cladding must meet a series of requirements to protect habitat from wind and water. In ecological construction, these coverings should also contribute to improving comfort in winter and summer and be harmoniously integrated into the environment surrounding the construction.
Wooden cladding
There is a variety of exterior cladding but the ones we will choose for our ecological construction are wooden claddings. Several criteria must be taken into account when making the final choice. Priority will be given to species produced locally or ate least in Europe and from sustainably managed forests. In his book on ecological construction, Jean-Claude Mengoni points out that wood is divided into task classes which depend on its use and the conditions it might face. He recommends maritime pine, Douglas pine, larch, walnut, chestnut, European oak or locust for cladding.
Net-like wood should be considered for highly exposed façades. This is obtained after intense drying and cross-linking, i.e. firing at very high temperatures in oxygen-free furnaces. The wood then contains only 4% moisture (compared to 12% for unheated wood). It it then more resistant to climatic aggressions and does not require any special maintenance.
Coatings
Coatings consist of three components:
- A filler: the structure of the coating (mostly sand)
- A binder: it ensures the resistance of the filler
- A diluent: it facilitates the adhesion of the filler to the binder
Lime-based coatings
Lime-based coatings are permeable to water vapor and thus allow the walls to breathe. In addition, lime protects the shell from bad weather tanks to its impermeability to runoff water. It is an interesting ecological alternative since its manufacture requires half as much energy as for a cement plaster and seven times less than for a synthetic plaster.
On the other hand, it must be combined with other materials (hemp, linen, perlite…) so that it contributes to the thermal insulation of the home.
There are two types of lime:
- Natural hydraulic lime which is composed of clay
- Air lime which is made of limestone with a slow air setting
Soil-based coatings
They are mainly composed of clay and sand, to which vegetable fibers can be added to strengthen the structure and limit shrinkage.
The soil-based coating is an excellent hygrometric regulator, natural, non-toxic, infinitely reusable and very economical. On the other hand, the soil is waterproof and the plaster will therefore have to be covered with a layer of air lime.
The soil of the land on which your ecological house will be built can be used as a plaster if it contains enough clay (between 15 and 20%).
Plaster-based coatings
The gypsum requires a slightly lower embodied energy than that required for lime and cement. It is permeable to water vapor and capillary.
The plaster and soil used in mixture have very interesting synergies in outdoor applications. Indeed, plaster reduces the shrinkage of the soil.
Viroc
Viroc is a composite panel made of a mixture of wood and cement particles. It can also be used indoors, on the floor and on the ceiling. It has the following advantages:
- Non-toxicity
- Good sound insulation characteristics
- Very easy installation
- Fire and insect resistance
- Good thermal resistance
- Waterproof and permeable to water vapor
