Which type of greenhouse heating system does not directly heat the air?

Infrared heating is a unique greenhouse heating system that does not directly heat the air. Instead, it operates by emitting infrared radiation, which heats objects and surfaces within the greenhouse, such as plants, soil, and structures. This form of heat transfer warms these objects, which then radiate the heat back into the air over time. This process helps maintain a more stable and comfortable environment for plant growth.

In contrast, other heating methods like convection heating, forced-air heating, and radiant floor heating can have more direct influences on the air temperature. For example, convection heating relies on the movement of heated air throughout the space, while forced-air heating uses fans to circulate warm air. Radiant floor heating can warm the air above it, but it primarily focuses on heating the floor, which then radiates warmth upward. Thus, infrared heating stands out due to its method of influencing temperature through indirect heat transfer.