Understanding Hydronic Heating Systems and How They Work

October 18, 2023
Heating Services in Seattle, WA

The majority of homes in the US have forced-air heating systems with a furnace or a heat pump. Forced-air heating is extremely effective, but it also has some drawbacks. Compared to forced-air heating, hydronic heating systems have many advantages as they are quieter, more energy efficient and improve indoor air quality. Learn more about hydronic heating, and decide if it’s the right choice for your home.

What Is a Hydronic Heating System?

Hydronic heating systems use hot water instead of just pumping heat out into the air like forced-air heating systems do. This type of system is often referred to as radiant heating, but the truth is that hydronic systems provide both radiant and convective heat. Convective heating is when a hot gas or liquid flows over or through a colder surface, which results in heat flowing out of the gas or liquid and into the surface so that it becomes hotter. Radiant heating is simply when a hot surface gives off heat to any objects or people in the surrounding area. For instance, the heat given off by a stovetop or oven is a type of radiant heating.

Hydronic heating systems have a boiler, which uses gas or electricity to produce either extremely hot water or steam. The heat produced by the boiler can be dispersed using standalone radiators, baseboard radiators, or through coils installed underneath the floor. The hot water or steam produces convective heating as it heats up the radiators or the floor. The heat then emanates from the floor or radiators into both the air and surrounding objects and surfaces to provide radiant heat. In places where it snows a lot, some people even choose to install hydronic heating tubes or coils underneath their sidewalks and driveways so that they stay warm and melt any snow that falls.

The hot water from the boiler can also be pumped through the AC coil inside the home to create a hybrid hydronic/forced-air heating system. In this type of system, the heat from the hot water is directly released into the cooler air flowing through the AC air handler, and the blower then moves the heated air around the building and blows it out of the supply vents just like a standard forced-air heating system.

All hydronic heating systems work in a closed loop. When the system is running, hot water or steam constantly flows through a series of pipes and into all the radiators or through the underfloor radiant heating tubes. The heat from the water or steam is constantly absorbed by the radiators or floor as it moves through the system so that the water begins to cool down. The cool water then flows back to the boiler so that it can be reheated before flowing back out into the system again. The fact that the system is a closed loop makes it more efficient as the water in the system is always recycled.

How Effective Is Hydronic Heating?

One of the main reasons that people are initially wary about installing a hydronic heating system is that they worry it won’t be as effective as a furnace and forced-air heating system. The truth is the opposite, as hydronic heating systems are more effective and will help to maintain a much more consistent temperature.

The reason is that a hydronic heating system raises the temperature of the walls, floors and even the furniture so that they always stay warmer, and the heat from these surfaces continuously radiates out to also increase the air temperature. In a forced-air system, the air temperature tends to decrease quickly when the furnace shuts off as the air always cools down when it hits cold walls, windows, floors, etc. With hydronic heating, all the surfaces will hold onto the heat effectively so that everything stays warmer even when the system is running. This means that hydronic heating works passively at times as the heated surfaces will continue giving off heat into the air for some time even when the boiler isn’t running.

Advantages of Hydronic Heating Systems

In addition to being extremely effective and helping to keep the temperature in a home more consistent, hydronic heating systems also have numerous other advantages. The biggest and most important advantage is that they are much more energy efficient than forced-air systems. In fact, a hydronic heating system can be around 10 times more energy efficient.

One issue with forced-air heating is that it can tend to produce cold spots in some parts of a room or home. The areas close to the supply vent where the hot air flows out will always be warm enough, but the places further away from the vents and near exterior walls, windows and doors will often stay cooler. This is another advantage of hydronic heating as it will distribute the heat around each room and the whole home more evenly and prevent cold spots from forming.

A hydronic heating system can also save you money by eliminating the need to have a separate water heater. Traditional boilers will only supply hot water to the hydronic heating system, but a combination or combi-boiler can also provide hot water to the home’s plumbing system. Hydronic heating is also almost completely silent, so you won’t have to deal with the constant noise of the furnace and blower like with forced-air heating.

Another major advantage of hydronic heating is that it allows you to create heating zones so that you can adjust the temperature for different rooms or different parts of the home independently. Hydronic systems also take up far less space since they don’t require ductwork. Hydronic systems are also better in terms of indoor air quality as forced-air systems will always spread dust, allergens and airborne pollution throughout the home.

There are a few minor drawbacks or downsides to hydronic heating systems as well. The biggest one is that they tend to be quite a bit more expensive to install. This is especially true if you want to install underfloor heating in an existing building as this would require tearing up and then replacing all your floors. This obviously isn’t an issue if you’re building a new home, but it would otherwise require quite extensive renovations. Despite the higher cost, a hydronic heating system will still typically be more cost-effective in the long term due to the increased energy efficiency.

Another thing to consider is that, while a hydronic system will keep the temperature more consistent and use less energy, a forced-air system will heat the home much faster. This isn’t an issue as long as you keep the system turned on, but it will take a hydronic system much longer to bring the home up to temperature if you turn it on when your home is more than a few degrees colder than your desired temperature.

Brennan Heating & Air Conditioning is the top choice in the Seattle area for boiler and hydronic heating installation, repairs and maintenance, and our certified HVAC technicians also install, service and repair furnaces and forced-air heating systems. We also offer expert cooling, electrical and water heater services, so give us a call today for any of your home service needs.

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