These systems use a water to water style heat pump. They can also supply air conditioning.
There are two basic styles of hot water based systems:
1. Geothermal and radiant floors.
Radiant floors and Geothermal go together well, temperatures are very steady and the floors are slightly warm.
The “gold standard” for radiant floors and geothermal is the” poured in slab” type, with an engineered laminate or tile finish. Track type tube on top of the floor will work but is less effective, stapled up from underneath is even less effective at getting heat out. Sometimes, to convert this type of radiant floor to Geothermal, we need to add radiators, or toe kick type hydronic heaters. This is because Geothermal hot water from this style heat pump becomes much more efficient the lower the water temperature is set.
Most radiant floors that are run on a boiler can be converted to Geothermal.
2. Baseboard and Radiators
Baseboard systems can also be converted to Geothermal by changing the baseboard to a similar style baseboard, with more pipe and fins in it. There are many radiant panels and modern style radiators designed to use the low temperature water. These can be added or converted as necessary. Towel warmer style radiators can be combined with radiant floors as well. Many homes with multi zone baseboard hot water are a pretty easy conversion, costing somewhere in the $40,000 range, including drilling, heat pumps, installation etc.