Hydronic radiant heating systems use large heated surfaces (floor, walls or ceiling) and can deliver enough thermal energy to heat a space with low fluid temperatures, typically less than 110ºF (43ºC) in cold climates of North America. The heated surface temperatures are even lower, typically lower than 80ºF (27ºC), depending on location and heat loads. Radiant systems are safe, gentle, steady and invisible. In a high-performance home or building, or any building with low heating loads, both fluid and surface temperatures are even lower.
When it's hot outside, solar gain impacts buildings through windows and heats the building envelope. Heat is also conducted through building surfaces from the hot outdoor ambient air, and through any air infiltration. For interior cooling, the most comfortable method to deliver thermal comfort is to surround occupants with cooler surfaces and increase the radiant heat loss from bodies. With radiant surface cooling, less cold air is required, which reduces the need for high air volumes and the resulting noise and drafts.
Depending on the climate zone, most buildings that utilize hydronic radiant cooling also cool and dehumidify incoming fresh air, keeping occupants comfortable with low air volumes. The dehumidified air actually reduces the need for the air to be so cold, while preventing any condensation on the cooled surfaces.