2) Using natural materials in a building will provide a healthy internal environment with a significantly better Indoor Air Quality. You will avoid the off-gassing of VOCs (volatile organic compounds) that can result from the use of uPVC and Vinyl finishes.
Natural building materials can be defined as those coming from renewable resources. Materials that are minimally processed, and are plentiful in the natural world. They include: Timber Straw Wool Stone Earth Lime
There are many benefits to using natural building materials, but the two most important are:
1) You will be using much less energy in the construction of your building. By their very nature, these materials have a significantly lower embodied energy than conventional materials such as concrete and plastics.