How Does a Boiler System Work: Boilers Vs. Furnaces

Ultimate Guide to Boiler Systems

There are many ways to heat a house. Some people are not even aware that some homes are heated via a boiler system, which is entirely different than your traditional furnace. We’re going to talk about boiler vs furnace systems, why one would choose one over the other, and more importantly answer the question, “How does boiler heat work?”

What’s a boiler?

A boiler heater warms your home via heating water and utilizing either hot water or steam. This is called hydronic heat. This is different than a furnace, which heats the air itself with a duct system and a blower. A boiler heating system might use propane, natural gas or a host of other types of fuels to heat the water. (It’s important to keep in mind that a boiler doesn’t indicate the type of fuel but the system in which it heats your house.) Boilers use pipes and furnaces use ducts to distribute the heat from its source. Often, older homes with cast-iron radiators have a boiler system.

What is radiator heat?

Radiators are a typical component of a boiler heat system. Hot fluid loops through pipes inside of a radiator, heating the room that it’s in. Steam radiators are either the typical cast-iron, free-standing systems made popular by companies from the 1800s such as the American Radiator Company, or a baseboard steam system, which are baseboards that blow out steam rather than hot air. These days, many people chose to go with the more modern electric radiators or ceramic radiators, which use safer materials to avoid dangerous levels of evaporation and aren’t always as hot to the touch.

How does a boiler work?

Using some form of fuel (such as natural gas), the boiler component heats the water. Then, the circulator pump or valves will move the heated water or steam through pipes. These pipes will lead into the radiators or baseboards throughout the house. Radiators will give off heat by warming the area with its steam or hot pipes; a radiator can be quite warm to the touch. One essential thing to keep in mind with how a boiler works is that a boiler won’t boil the water. So then, what does a boiler do? It usually gently heats it to around 150 degrees, which is hot enough to create steam.

How does radiator heat work?

Radiators are a type of heat exchange patented all the way back in 1855, which pulls hot fluid or steam through exposed pipes, which heat the air around the pipes through convection.

How does a furnace work?

Furnaces create forced-air systems. A fuel source (like propane or natural gas) will light a burner, which heats incoming air. A blower will push that hot air into a system of ductwork. Warm air fills the rooms, and cold air is sucked back to the furnace.

Boiler vs. Furnace

Those wondering how does a boiler system work differently should understand that these two systems use different means to heat the house: Furnaces move around forced air and boilers move around steam to heat the air. Here is a list of some of the many other major differences:

Factors Boilers Furnaces
Installation Because it requires a system of pipes, boilers tend to be more expensive to install than furnaces. Furnaces themselves tend to be cheaper than boilers, but installing ductwork to push the forced air can be expensive.
Surface Heat Old, cast-iron radiators are often hot to the touch, giving a risk of burns. (Modern radiators are usually less likely to lead to burns.) Usually, no part of a forced-air system will burn you except for the burner itself, which can be hard to access.
Noise Many people who aren’t used to radiators will become alarmed at the sudden tapping, whistling or almost spooky sounds! Furnaces tend to not be as noisy. While they do occasionally click or blow air, if your furnace is making a lot of noise, that may be an indication that some parts need to be replaced.
Energy On the whole, boiler systems to be either about the same or more efficient than forced-air systems, since there is no efficiency loss due to ducts. That being said, older systems can and should be optimized for better energy usage. When comparing radiator heat vs forced air, force air systems tend to be either about the same or less efficient than boiler systems. This is because there’s often efficiency loss in the duct system.
Air Quality Boiler system heating is preferable to those with allergies and dust sensitivity. It’s one of the top reasons to choose boiler heat vs. forced air. Because the same air circulates, dust and allergies can be worse than with boiler systems. It can also be a bit drafty.
Reliability Radiators and boilers are often considered to be quite reliable with very little maintenance. That being said, leaks can do quite a bit of damage when they happen. With regular furnace maintenance, the system will last about 15 years or more.
Common Issues/Fixes Issues can arise when a radiator tilts, blocking water from returning to the rest of the system. Air might get into the system. In extreme weather conditions, the water itself can freeze and burst pipes. Issues usually arise from a broken igniter, a broken blower or gummed-up ductwork.


If you’re wondering what kind of system you have or how to make sure it will keep working for many years, schedule an appointment with us!

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