Hydronic distribution systems use ________ as methods of heat transfer.

In hydronic distribution systems, heat is primarily transferred using water as the medium, and convection plays a crucial role in this process. When water is heated in a boiler, it circulates through pipes to radiators or other heat emitters. Here, the heat is transferred from the hot water to the surrounding air mainly through convection, as the air in the vicinity of the water heats up and rises, allowing cooler air to take its place.

While radiation does occur when warm surfaces emit heat, especially in cases of radiators or baseboard heaters, the primary mechanism for heat transfer in these systems depends significantly on convection. Thus, even though radiation is present in the context of some heat emitters, the dominant method of heat transfer in hydronic systems is convection.

Other options may suggest that conduction alone is significant or combine with other methods, but convection is essential in the context of fluid-based heating systems like hydronics, making the correct focus on convection an important aspect of how these systems function.