What is a Condensing Furnace, and Why Should I Have One?

Posted: 2022-11-17

If you’re a homeowner who wants to get the best performance out of your heating system, then you should pay close attention to your furnace's efficiency rating. If you want a unit that comes with the best energy efficiency, you should install a condensing furnace in your home.

Four Seasons Air Specialists is your trusted heating company in Lino Lakes MN. We are experts at determining the right furnaces for homes, making sure total comfort and energy efficiency are achieved.

AFUE Defined

The efficiency of a furnace is measured by annual fuel utilization efficiency (AFUE), which is a measure of how efficient the system is when it comes to converting the energy in its fuel to heat over a typical year. (Source: energy.gov)

AFUE doesn’t include the lost heat due to leaky ducts, which can account for as much as 35 percent of the energy output, especially when the ducts are located in partially or unconditioned spaces such as the attic or garage. The quality of insulation also plays an important part in the overall performance of the heating system.

As mentioned earlier, a furnace with at least 90 percent AFUE is considered a high-efficiency unit or a condensing furnace, which means that 90 percent of the fuel becomes heat for the home and 10 percent is used in the heating process. Today, you can get as much as 99 percent of heat from each dollar you spend on fuel by investing in a 99 AFUE condensing furnace.

Understanding Condensing Furnaces

A condensing furnace works similarly to a regular gas-fired unit. The heating cycle starts with the thermostat, which detects when temperatures drop inside your home. It then activates the furnace. Next, the burners inside the furnace ignite, creating heat that’s captured by the heat exchanger. Then, a powerful fan blows air across the heat exchanger. The air absorbs the heat and is then forced into the ducts, and distributed throughout your home. The exhaust gases are vented outdoors, making sure that you do not breathe in unnecessary gas.

A condensing furnace filters and reheats return air from your home in a continuous cycle. Most of this air is simply distributed over and over, but more than that, a small amount of fresh air is usually pulled in through cracks around windows and doors and other areas.


A condensing furnace uses electronic ignition, such as a hot surface igniter. This type of igniter is assembled with a strong silicone nitride material to prevent the formation of cracks. Once the thermostat detects the temperature in your house is below the minimum settings, it will distribute an electrical signal to the hot surface igniter in the furnace. Then the temperature of the igniter will increase to 3000°F or lower depending on the furnace model. This type of furnace will help you save money on your energy bills each month because it no longer uses a standing flame.

Condensing furnaces deliver outstanding, consistent air distribution. Since these systems operate longer at a lower setting than conventional units, your home will have a uniform temperature, resulting in greater comfort.

Another benefit of using a condensing furnace is that it features variable-speed blowers. This technology allows you to customize the flow of heat and air throughout your home based on your exact preferences. These blowers give you the ability to meet changing heating needs within your home without the added cost that would come from running a standard furnace at a higher setting just to get the same result.

The supply lines, combustion chambers, and flues are sealed from the inside of homes thus preventing exhaust gases from leaking or being back-drafted into occupied spaces. Due to these features, condensing furnaces require slight modifications with installation and are usually more expensive than standard-efficiency models. However, their increased efficiency means they typically last longer, compared to furnaces with lower AFUE ratings.

Questions? Ask Four Seasons Air Specialists

While investing in a condensing furnace involves a higher upfront cost, the unit will practically pay for itself as you enjoy lower monthly heating costs throughout its lifetime (with proper maintenance). As your preferred Centerville furnace repair and installation company, we guarantee the proper setup and functioning of your brand-new high-efficiency furnace.