Radiant heat is the most comfortable heat. Typically, it is installed as a warm floor. Hot water is heated via a boiler, and circulates through the floor, heating the floor. Then, the floor radiates the heat upward, warming the home. For advanced efficiency, add an indirect-fired water heater to heat the domestic water. Matching a high efficient boiler with an indirect-fired water heater will deliver virtually limitless hot water for bathing, laundry, dishwashing and cooking at a lower operating cost compared to most other alternatives. When installed as a combination unit, you'll have the most efficient and comfortable heat. And hot water at twice the peak flow of a tankless. The photo here shows the boiler and indirect water heater installed in combination. A recent install by Wayne Maples Plumbing & Heating. Win! Win!