Hydronic Heating Systems Hydronic Radiant Heating & Baseboard Heating

Hydronic Heating Systems Hydronic Radiant Heating & Baseboard Heating

Hydronic Heating Systems

This homeowner wanted to build an ultra energy efficient heated barn, comfortable enough to be used as a recreation room or extra living space on the weekends, and not too costly to maintain. Larry Janesky of Dr. Energy Saver explains how the objective was accomplished.

All hydronic heating systems have one thing in common: hot water. Hydronic heating systems provide warmth by pumping hot water to radiators, to under-floor tubing, or to heat exchangers.

Hydronic heating offers a number of advantages and just one limitation

People who have allergies and respiratory ailments often prefer heating with radiators or hydronic radiant floors because these heating systems don’t blow air around like forced-air heating.

Forced-air systems increase the amount of airborne dust and other irritants that people have to breathe.

Hydronic baseboard heat and hydronic radiant floor heat warm a room from the floor upwards, rather than from the ceiling downwards, which is what forced-air heat typically does. Putting the warmth at floor level is more comfortable and more effective than having the warmest air near the ceiling.

A well-designed hydronic heating system can be very economical in terms of energy use. This is especially true when a high-efficiency condensing boiler or a tankless water heater is used as the main hot water source. For even greater savings, it’s possible to install a solar thermal system that will allow the sun to do some of the water-heating work.

One disadvantage with most hydronic heating is that a separate air-conditioning system will need to be installed if homeowners want to have central air conditioning during warm weather.

With forced-air heating, the same ductwork system that distributes heated air during cold weather can be used to convey cool air to the living space. If you want to have hydronic heating as well as central air conditioning, a hydro-air system (explained below) is a good option.


  • Baseboard. This popular hydronic system is frequently referred to as «hot water baseboard.» The painted steel housing on the baseboard unit hides a hot water pipe surrounded by metal fins that help radiate the heat.
  • Hydronic radiant floor. This heating system uses the entire finished floor as a giant radiator. Hot water is pumped through plastic tubing installed beneath the finished floor surface. A hydronic radiant floor can be installed beneath tile or wood; it can also be embedded in a poured concrete slab. It’s not a wise choice beneath wall-to-wall carpet because the carpet doesn’t conduct heat very well. Hydronic radiant floor heat is difficult and costly to retrofit. The best (most affordable) retrofit situation is when tubing can be stapled to the underside of the subflooring from an unfinished basement.
  • Hydro-air heating. This heating system requires ductwork and at least one air handler. Hot water is pumped to a heat exchanger located in each air handler to warm air before it’s distributed throughout the house. Hydro-air systems are usually more affordable than hydronic radiant floor heating, and they offer the advantage of a ductwork system that can also be used for air conditioning.

Today’s boilers are far more compact and efficient that older models. This wall-hung unit provides hot water for a two-story home that combines radiant floor heat and baseboard radiators. It also supplies domestic hot water needs.

Boilers & other hot water heaters

There are different ways to heat the water used in a hydronic heating system. The most common heater is a boiler fueled by natural gas, propane, or fuel oil. Some hydronic heating systems rely on heat pumps, tankless «on-demand» water heaters, or even tank-type water heaters.

The sun is another possible heat source. In a solar thermal system, the sun heats water or an antifreeze solution in a solar panel. When the liquid in the panel reaches a certain temperature, it’s pumped down to the hot water tank or to a heat exchanger in the tank. A backup heat source is required for periods when solar energy isn’t available.

In any hydronic heating system, there will be a pump that moves the water, piping that conveys hot water to the living space and transports cooled water back to the heat source, and radiators that absorb and radiate heat.

The thermostat is a final common ingredient. It tells the heating system when to pump hot water to the radiators so that comfortable temperatures can be maintained. Choosing the right type of thermostat is important with a hydronic heating system.

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