Choosing the right insulation materials

Whether you are looking to build an ecological or standard property, insulation plays a key role in ensuring optimal comfort and saving energy.

Before choosing an insulation material, think about the installation. Depending on the location of the insulation, certain forms are to be preferred (bulk, panel, roll, etc.) and may influence the choice of material. Finally, be careful when installing the insulation: if it is badly installed, all the properties of the material will be altered.


To make the right choice from the long list of insulators available on the market we have taken time to outline some of the most important factors. 

In passive house construction, excellent insulation of the external building envelope is one of the 5 pillars of this building concept. Poor insulation can lead to high heat loss, discomfort in the house, and even signs of mould. It is therefore necessary to pay particular attention to the choice of insulation material:

Embodied energy:  In a green building project, it is important to consider the embodied energy of a material, i.e. the energy required to extract, manufacture and transport the material. Bio-sourced insulation materials are largely known for their low embodied energy.

Low embodied energy insulation would for example be linen fibre & hemp fibre.

Thermal performance level: To identify the thermal performance of an insulation, two main indicators should be taken into account: 

  1. Thermal conductivity (lambda): The ability of the material to transmit heat by conduction. This determines the insulating capacity of a material: the lower the lambda coefficient, the more insulating the material.

  2. Thermal resistance (R): The ability of the material to resist cold and heat. The R-value depends on the thickness of the material and the thermal conductivity.

Insulation with low lambda coefficients are hemp fibre & cork fibre


Humidity control: The humidity control of an insulation material is its ability to absorb and release humidity efficiently without deteriorating. Insulation with good humidity control ensures dry and healthy indoor air for the occupants.


Examples of insulation with good humidity control are wood fibre & cellulose wadding


Non-flammable or fire-protected: 

Some insulation materials are considered non-flammable and can even protect against fire by slowing the spread of flames. This is the case for some mineral insulation materials (made from sand, recycled glass, clay, etc.).

Examples of non-flammable insulation are foam glass & rock wool

Resistance to rodents: Rodents can cause serious damage to a building’s insulation by burrowing into it and this can significantly alter the insulating properties of the material. If possible, make sure you choose an insulation that will also be resistant to insects.


Examples of rodent-resistant insulation are expanded cork and hemp

Health risks: 

Some insulation materials can cause respiratory problems (e.g. rock wool) or emit toxic substances in case of fire (e.g. polyurethane). Insulation has a role to play in maintaining healthy air in the home.

Examples of non-harmful insulation are wood fibre & hemp

Durability: For insulation to last it must be resistant to external aggression eg rodents, insects or humidity but also not settle over time (which is the case with cotton wool or linen, for example).


Examples of insulation with good durability are wood fibre & straw