This research studied the combustion of wood exposed to low-temperature for an extended duration. A new evaporation approach was developed for low-temperature extended heating of wood. Evaporation was modeled as a boundary condition for initial drying, and internal evaporation term was re-introduced for extended heating model. A porous model was developed through the use of effective transport properties that enabled a reliable representation of heterogeneous medium of wood to be achieved by a homogenous model. Darcy’s law was modified to account for inertia and boundary effects on the flows in a porous structure. The numerical model showed that the free water movement produced constant temperature distribution for initial phase. As heating continued, the transport of combined moisture was strongly coupled with temperature field development. The numerical solution illustrated the importance of the interaction of moisture flows and temperature development for self-heating.