What method of heat transfer heats the exterior of a building the quickest?

Radiation is the method of heat transfer that heats the exterior of a building the quickest. Unlike conduction and convection, which require a medium (such as a solid for conduction or air for convection) to transfer heat, radiation involves the transfer of heat through electromagnetic waves. This means that heat can be transferred through a vacuum or across distances without needing a physical medium.

In the context of a building, when sunlight (a form of radiant energy) hits the exterior surfaces, it rapidly heats those surfaces through direct radiation. This is especially significant in warmer climates or during the daytime when solar radiation is at its peak. The surfaces then may conduct the heat inward, but the initial rapid heating effect occurs through radiation.

Convection involves the movement of air to facilitate heat transfer, while conduction requires direct contact for heat transfer to occur. Both methods are generally slower in comparison to radiation when considering how quickly the exterior of the building can heat up from an external source like the sun.