Radiant heat in HVAC is a type of heating system that uses radiant energy to transfer heat from a heat source to a space or object. Radiant heat is a form of energy that travels in a straight line from the heat source to the object, warming it directly without having to heat the air in between. Radiant heat systems are typically powered by electricity, natural gas, or hot water, and can be used to heat floors, walls, and ceilings. Radiant heat systems are often used in combination with other HVAC systems to provide efficient, comfortable heating.