What method of heat transfer is most likely to extend fire involvement on the leeward side of a building?

The most likely method of heat transfer that extends fire involvement on the leeward side of a building is through convection or radiation.

When a fire is burning, it generates heat that can be transferred in multiple ways. Convection involves the movement of hot gases and smoke, rising and spreading horizontally. This can lead to ignition of combustible materials on the leeward side, where the heat is carried by the rising smoke and air currents.

Radiation also plays a significant role, as the intense heat produced by the flames can radiate outward, warming surfaces that are not directly involved in the fire. This radiative heat can ignite materials away from the fire source, especially those that are on the leeward side, following the path of least resistance for fire spread.

Both convective currents and radiant heat can significantly extend fire involvement beyond the immediate area of the fire, making them the primary methods responsible for fire spread in such scenarios.