Physical properties of wood
Charpentes en bois

Table 1 in gives some of the thermal conductivity coefficients frequently used in insulation calculations.

Because of its low conductivity, the insulating nature of the charcoal produced by its combustion, the relative insensitivity of its mechanical characteristics to temperature and the practical absence of thermal expansion, wood is without doubt the material whose behavior in a fire is the healthiest and, above all, the most...