How to insulate the roof of a wooden house outside

Wood has good thermal insulation and waterproofing, so it is so comfortable to live in wooden houses. However, not all elements of the house are made of solid wood. For example, the roof is made of prefabricated materials that make up ceilings and beams. Therefore, gaps and cracks form between individual elements. That is why an important question arises: how to insulate a wooden house. When to start warming the roof