We promote the use of natural materials where practicable as there are advantages for the environment and health as well as building fabric. For older buildings the use of natural materials is even more important as they work in harmony with the existing building fabric in the way they manage moisture and have a much lower risk of causing damage to the building fabric. Modern man made materials such as foam insulation and concrete render can trap moisture in the buildings fabric as they are impermeable to water vapour and liquid water. In contrast wood fibre and other natural insulation products allow the passage of water vapour and also liquid water as does lime mortar and render.
There are instances where it is not always possible to use natural insulation materials, such as below ground. XPS insulation is often used below ground as it does not absorb water and is a high performing insulator.