Steam vs. Hot Water Radiators – Which one to Choose?

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Vintage cast-iron radiatorImage by Peter H from Pixabay

Steam or hot water radiator heating system? Which type is better?

Find out how to choose a radiator that will provide the most comfort, easy installation, reliable operation, meet heating requirements, and deliver a cost-effective solution.

With the heating and cooling costs as the leading expenditures for North American homeowners, it is important to know the type of HVAC system you need or exist in a house you are looking to buy, especially if it is a historic home or older apartment.

Radiators are available in various sizes, styles, and heat outputs, so in order to buy the proper type, you might need professional help.

Aluminum, cast iron, steel, steam, and hot water radiators are popular heating devices designed to transfer heat energy from one medium (steam or hot water) to another (air), increasing the ambient air temperature and heating the space. Each type has its own pros and cons, and below are several to compare when choosing the best radiator for your home.

Here we will compare steam vs. hot water radiators only and show you the differences, common features, how they work, advantages, and disadvantages of both.

What are the steam radiators?

Steam radiators utilize steam as the heating medium, which forms when the boiler heats water above the boiling point. This is an old-fashioned heating method and is no longer the preferred home heating method. And one of the reasons is that the steam radiators operate with higher temperatures and have higher heat loss, making them less efficient than the hydronic system.

The main benefit of steam is that it tends to travel up a set of pipes, making it very easy to distribute the heat, especially in tall buildings and multi-residence dwellings, without using the pumps.

Steam radiators often work with a one-pipe system that delivers steam to the radiators and uses the same pipe to move the condensate back to the boiler. They can also work with the two-pipe system, using one pipe to deliver steam and a second one to transfer the condensate back to the boiler for reuse.

Many years ago, steam heating was fairly present in both residential homes and commercial buildings, mainly using cast iron radiators installed on the floor. Cast iron radiators are bulky, heavy and not cheap, but are great heat conductors that can emit heat for many hours even after the boiler turns off.

Today, cast iron radiators using steam are rare to see, while those using hot water can still be found in remodeled Victorian-type homes and historic buildings due to their unique vintage look.


  • Cast-iron steam radiators are very efficient in heating up the room.
  • Excellent conductors of heat.
  • Hot steam radiators can hold the heat for the longest period of time.
  • Professionally installed and regularly maintained steam radiators are very reliable and high-performing.
  • Due to quality materials (cast iron), steam radiators can last very long with no leaks and damages.
  • Due to their vintage look, steam radiators are very appealing.
  • When compared to forced air systems, steam radiators are quieter.
  • You can turn on or off heating to certain rooms, reducing heating expenses.
  • Due to better air quality, they are healthier to use than air forced systems, making them better for allergy sufferers.

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  • Expensive to buy and install.
  • Heavy.
  • Hard to provide zone heating, making some rooms more or less hot than others.
  • As opposed to air-forced HVAC systems, houses with the radiator system do not have air conditioning, making it costly to retrofit.
  • These systems often produce an annoying hissing sound.
  • Due to high steam temperatures, the flooring underneath the radiators can be damaged or lose its original appearance.
  • Leaky radiators can lead to injuries and property damage.
  • It takes time for the radiators to warm up.
  • Slower to react to the temperature change.
  • Cast-iron steam radiators take up more space than aluminum or steel panels.
  • They operate under higher pressures and temperatures, which are not safe.

Interested in hot water radiators?

Photo: Pixabay

Hot water radiator systems (hydronic) often use a circulation pump to move the hot water from the energy source, such as boilers, to the radiators, using a one or two-pipe system. In two-pipe systems, radiators have two pipes attached at opposite ends.

As the radiator releases heat to the ambient air, hot water becomes cooler, sinks to the bottom, and then goes back to the boiler for reheating and recirculation.

Old-fashioned hydronic radiators were made of cast iron, while modern hot water radiators systems use aluminum and steel and are often installed on the wall for space-saving. They are less noisy than steam radiators, have lower maintenance, and are more energy-efficient.

Water radiators often come with thermostatic radiator valves to control the room temperature by changing the water flow. The valve connects pipes to the radiator, and it can self-regulate depending on the room temperature.


  • Long-lasting heat. Even after turning off the heat source (furnace or boiler), radiators can still emit heat and deliver a cozy feeling for hours.
  • Due to their great conductivity, both aluminum and steel radiators can warm up fast and deliver heat to the surrounding air in no time.
  • As with the steam radiators, there is no air movement that causes dust and allergens circulation throughout the house.
  • Hot water radiators made of aluminum and steel sections (columns) are easily customized in terms of size. The aluminum-type radiators come with fins for efficient heat transfer.


  • Expensive to install.
  • Since radiator systems are made for heating only, adding an air conditioner requires expensive retrofits.
  • As opposed to cast iron steam radiators, aluminum and steel can cool off fairly quickly. Due to weaker construction, aluminum and steel radiators last less than the cast iron type.

How radiators work

In general, steam and hot water radiators look almost the same and work similarly. Radiators use heat exchange and natural convection to heat the space. The heat source (powered by gas, oil, or electricity) heats up the heat exchanger and then water inside the boiler. Heated water or steam then moves to the radiator, exchanging the heat with the surrounding air. Due to the high heat conductivity and great performance, today's radiators are made from steel and aluminum.

The cool air is pulled in at the bottom of the radiator, warmed up while passing over the radiator, and then released at the top. For the best outcome, it is important to install them under the windows or nearby the doors and ensure there is free air movement. Cold air at the bottom and warm air above the radiators makes the air circulate without the need for fans.

Tip: Radiators can break and leak. You might find a radiator not working upstairs but being too hot downstairs, or one part of the radiator is hot and the other only warm to the touch. Or there might be some strange noise. For any issues with the radiator system, it is recommended to call a plumber to check the condition of the radiators, fill them up with water, or bleed the air if necessary.

Steam radiators use steam formed when a boiler heats water above the temperature of boiling. The steam travels through the pipes and into radiators, transferring the heat to the ambient air. The steam then cools to the point when it turns into condensate (water), going back down the pipes and into the boiler, where it starts the cycle again. Since the system doesn't require pumps, it is hard to control how steam moves through the system, sometimes leaving homeowners with uneven heat distribution.

Hot water radiators work similarly to steam radiators, but instead of steam, the boiler heats water without creating steam and uses pumps to circulate water through the pipes and radiators. Once it transfers heat to the surrounding air, water cools down and returns back to the boiler, where it is reheated again. Hot water radiators are safer because they do not operate with the high pressure and temperature of the heating medium as steam radiators.

Tip: Before buying a new radiator, see how much heat output in BTU you need.

Do I have steam or hot water radiators?

If you just bought an old house, or an apartment in a historic building, which uses a radiator system for space heating, you might be asking yourself whether you have a steam or hot water radiator.

Sometimes it is hard to distinguish which type you have solely based on the look of the radiator. Or, based on how many pipes it uses, because both steam and hot water radiators can use one or two-pipe systems.

In general, cast iron and column radiators are used for both hot water and steam heating, while aluminum and steel panels, including baseboard radiators, operate mostly with hot water. In addition, one-pipe systems are often found in steam heating systems.

Another way to see the difference is by paying attention to the noise the system makes. The hissing sound is identification that you have a steam radiator while water dripping or trickling sound – hot water radiator system.

As the hot water systems operate in the closed system, they always have an expansion tank, while steam systems don't.

Also, the small bleed valve installed on the top of the radiator used to remove the trapped air means you have a system with hot water. In the case of the steam heating system, there is an air vent on the side.

Choosing a radiator style

There are several types of radiators you can select, and here are the popular ones:

  • Panel radiators
  • Column radiators
  • Cast iron radiators
  • Baseboard heaters

Panel radiators

Panel radiators use corrugated panels for the combined convection and radiate heating, offering great heat output, efficiency, and a higher comfort level. They are suitable for installation in most homes with central heating using hot water. These flat radiators provide a higher surface area for effective heating, taking less space than other types. Thin and lightweight design allows flexible wall mounting with horizontal or vertical orientation.

Column radiators

Column radiators are known as traditional radiators and are often found in Victorian-style homes and older buildings. They are designed with two hollow horizontal steel tubes connected with hollow steel columns welded to both ends. Column radiators are often made three or four columns deep. As each column is separated and because they have more surface area, air can easily pass through and receive heat more effectively. They are characteristic for older dwellings using steam as the heating medium, also in modern environments that utilize hot water.

Cast iron radiators

Cast iron radiators look similar to column radiators and can also use steam and hot water as a heating medium. Due to their solid construction, heavyweight and large size, they are often installed directly on the floor. The main advantages over other radiator types are long life, better resistance to rust and damages, and its ability to retain and emit heat longer.

Vintage cast iron radiators are not only beautiful additional to any home, but they conduct heat exceptionally well. You can really feel the warmth by standing next to it. It gives you cozy and comfortable sensations, and you can use its heat to dry wet clothes fast and easy.

Baseboard heaters

Baseboard heaters (radiators) are ideal for rooms with insufficient vertical space for its installation and where other radiator types (due to the height) cannot be installed. They mostly use a coil of copper pipes that carries hot water and aluminum fins attached to the pipes to improve the heat transfer.

Making the right choice

Whether you are renovating your beautiful historic Victorian home or a modern city apartment, radiators can be a great way to improve your comfort efficiency and update the look of your home. By choosing the right type and heat output (BTU), your radiator heating system will provide clean, reliable, comfortable, and effective heating whenever need it. Always consult a professional for the best result, peace of mind, and satisfaction.

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