A hot-water boiler heats water to 140–180°F and circulates it through a closed loop of pipes to baseboard radiators, cast-iron radiators, or radiant floor tubing. The water returns to the boiler, is reheated, and the cycle repeats.
Key components include the boiler itself, a circulator pump (or multiple pumps for zoned systems), an expansion tank to absorb pressure changes as water heats and cools, a pressure relief valve, and zone valves or thermostats for each heating zone.
Hydronic systems are valued for even, comfortable heat — no blowing air, no dust circulation, no dry air. Radiant floor systems are especially comfortable because heat rises from the floor up through the living space.
Modern condensing boilers (Weil-McLain, Navien, Burnham) achieve 90–98% AFUE by extracting heat from flue gases that older boilers exhaust. Upgrading from a 70% AFUE unit to a 95% unit can meaningfully reduce heating costs.
Information provided is general guidance for homeowners. Every home is different — contact DMES LLC for advice specific to your situation.