Your furnace is the powerhouse behind your home’s heating system and essential to day-to-day comfort. From cold, rainy spring days to snow and ice storms in the winter, it’s critically important to have a reliable furnace. The last place you want to be on a winter day is stuck inside without a properly working furnace.

Types of Furnaces

When it comes to heating your home, there are two common heating systems: forced air or radiant heat.

1. Forced Air Systems – This is the most popular type of HVAC system; it requires ductwork to blow (or force) the heated air throughout the house.

Forced air systems in a residential home.

2. Radiant Systems – A radiant system relies on boilers to send heated water (steam) through a series of pipes to radiators (or baseboards). Radiant systems are also used to create heated floors throughout the home.

Radiant system in a residential home.

Two lesser-known options are the eco-friendly solar panel heat or geothermal heat sources. These are rarely used because of the combination of high cost and low effectiveness in most areas. Most homeowners are familiar with forced air systems so that is what we will concentrate on.

There are 5 types of furnaces, the biggest difference is their energy source:

  1. Natural Gas – This is the most popular type of furnace. Natural gas offers an effective and cost-efficient heat source for homes across the country. Gas furnaces cost more upfront than electric furnaces, but the cost is offset quickly by lower monthly operating costs. Gas furnaces require regularly cleaning ductwork, annual inspections of the main unit and replacement filters.
  2. Oil – Oil furnaces are not as popular as they once were because of the volatility in oil prices. However, they remain a good choice for areas with harsh winter weather. If you have an oil furnace, you must also have a fuel storage tank on your property, which is an additional cost and space consideration. Oil furnaces are appealing because there is no monthly utility bill, you simply pay to fill your oil tank when necessary.
  3. Electric – If you live in an area with very mild winters, an electric furnace might be your best option. They have very low upfront cost and little maintenance but are expensive to operate. Therefore, they are generally used in areas where the outside temperature doesn’t ever get below freezing throughout the year.
  4. Propane –  A propane furnace runs from propane tanks stored outside the home, like an oil furnace. However – because of the cost involved with a propane furnace, they are typically used only in areas where either natural gas or oil aren’t readily available. Today, about 10% of homes use a propane heat source.
  5. Wood – A wood-burning furnace is the most fundamental source of heat. Wood-burning furnaces are a viable option in areas where firewood is plentiful and affordable. Wood is burned in a firebox and the heat is circulated through ductwork. Because wood burning furnaces must be fueled manually, they can’t be left on when you leave the house. For this reason, a wood furnace is often used in combination with an oil or gas furnace. A wood burning furnace is effective and simple, but very antiquated by today’s HVAC standards.

Types of heating systems for residential homes.

How It Works

Each type of heating system works slightly differently. Depending on which type of furnace you have, it will work slightly differently than the other types.

  • How a Gas Furnace Works – In most American neighborhoods, natural gas is sourced under the ground. A pipe transports gas from your local source and brings it into your home directly to the furnace. After the gas enters your furnace, it is lit by the burner. This burning gas heats up cold air from the outside. The now-warm air is pumped throughout your home through the vents in each room. Once the thermostat senses a comfortable temperature has been reached, it switches off the gas valve to prevent the flow of warm air.
  • How a Propane Furnace Works – A propane heating system works similar to a gas furnace – the fuel is burned, and hot air is pumped through the ductwork. However, propane has a few key differences. First, there is not an intricate network of propane supply lines across the country. Instead, propane must be stored in tanks on the property. This is why propane furnaces are most often used in remote areas where other energy sources are scarce or can’t be delivered. Once the propane fuel is delivered from the tank to the furnace, it is burned, and the heated air is blown throughout the home. Once the air has cooled, it’s returned to the furnace and recycled.
  • How an Electric Furnace Works – An electric furnace produces heat with electric heating elements instead of burning fuel. Circuit breakers control the heating elements, sort of like a giant hairdryer. Electric heating systems are easy to run, simply plug them in and turn them on when you need them. However, they are expensive due to the high cost of electricity in most areas.
  • How an Oil Furnace Works – When activated, the oil furnace begins to draw oil from a reserve tank into the burn chamber. Here, the oil is converted into a mist and sprayed onto the burner where the hot air is pushed through your duct system.
  • How a Wood-Burning Furnace Works – Wood-burning furnaces generate heat by burning wood in a firebox and circulating the heat through existing ductwork. However, the wood must be fueled manually, and the fire must be tended, so it’s not a great option if you’re going to be leaving the house during the day. Because of this, wood burning furnaces are often used in combination with an oil or gas burner as a backup heat source.

Parts of Each Type of Furnace

Every heating system creates heat; therefore, they all have similar parts. No matter what type of furnace you have, you’ll find these parts in common:

  • A blower to move the air
  • A filter to sift out particles
  • A thermostat to regulate temperature
  • Ductwork in the homeThe four parts of a heating system.

Other than those common components, each type of furnace has specific parts that allow it to function properly.

Parts of a Gas/Propane Furnace –

  • Supply plenum
  • Hot surface ignitor
  • Burners
  • Heat exchanger
  • Flue

Parts of a gas heating system.

Parts of an Electric Furnace –

  • Heat Elements
  • Heat Relays
  • Plenum
  • Power Relay
  • Electrical Transformer
  • SequencersParts of an electric heating system.

Parts of an Oil Furnace –

  • Furnace controls
  • Heat exchanger
  • Burner assembly
  • Fuel pump and motor
  • Combustion blowers
  • Cleanout and observation ports

Parts of an oil heating system.

Parts of a Wood-Burning Furnace –

  • Firebox
  • Air Vent Controls
  • Baffle
  • Flue Collar
  • Stove Pipe
  • Flue
  • Doors
  • Ash Pan
  • Damper
  • Catalytic CombustorParts of a wood burning heating system.

Common Furnace Problems

No matter what type of heating system you have, the same basic problems plague furnaces during the cold months. Everyday maintenance will go a long way in preventing expensive repairs, but here are some of the most common furnace problems and where they occur.

1. Cracked Heat Exchanger – This can be a very expensive repair that is easily preventable with regular maintenance.

2. A Dirty Filter – A dirty filter makes your unit work harder and wear out faster.

3. Slipped or Frayed Blower Belt – If your unit is making a high pitch squeal, this is likely the culprit.

4. Ignition or Pilot Control Problems – When the unit isn’t heating properly, it’s often due to a problem at the pilot light or ignition.

5. Thermostat – Sometimes the issue is with the thermostat on the wall, not with the furnace. Changing the thermostat batteries should be the first step to diagnosing a furnace issue.

6. Yellow Pilot Light – This is a sign of excessive carbon monoxide. Leave the home and call a professional immediately.

7. Worn Out Ball Bearings – A scraping sound indicates that your ball bearings are wearing out and it’s time to call a professional.

Worn out ball bearings need to be replaced.

8. Frequent Cycling – This could be caused by several issues including a clogged filter, improper airflow, or a bad thermostat.

9. Limit Switch – If your furnace is continually blowing nonstop, it might be a problem with the limit switch.

10. General Mechanical Problems – Loud sounds, low airflow, or insufficient heat can be due to a few general mechanical problems in any furnace.

When to Repair or Replace

When your heating system isn’t working as it should, it can be difficult to know when you should have your system repaired or replaced. While each situation is different, these guidelines will help you learn about the best time to service or replace your furnace.

  • Age – According to the U.S. Department of Energy, a furnace should last between 15-30 years. If your furnace was installed more than 15 years ago, it’s likely time to consider a replacement.
  • Emitting Carbon Monoxide – This is a serious safety hazard. If your furnace is emitting carbon monoxide, it is due for an immediate replacement, regardless of how old (or young) the system may be.
  • Cost of repair – If you’re faced with a repair estimate that is over half of the cost of replacement, and your unit is older than 15 years, you are better off putting your money into a new system rather than repairing your old one.

Cost of repair versus replacing.

  • Increased electric bill – If you notice an increase in your electrical bill, it’s likely because your furnace is getting older and working harder than necessary. This trend will likely continue until the furnace is replaced.
  • Less effective – If your furnace is less powerful than it was last winter, and seems to be getting weaker, it might be time for a replacement.
  • Frequent repairs – No one wants to be stuck with a furnace that needs to be repaired over and over again. If you’re facing yet another repair bill – it might be time to replace the unit.
  • Strange noises – Most heating systems should be relatively quiet, except for the quiet hum of the fan or motor. If your system is noticeably louder than usual, it could be the sound of a wearing-out process.
  • Selling Your Home Soon – A new furnace can be a big selling point for home buyers. If you are considering selling your home, replacing the furnace now might be an investment that will pay off later.

How Much Does a New Furnace Cost?

The average cost of a new furnace is $1,500 to $6,500. That is a $5,000 spectrum, so what makes the big difference on a $1,500 furnace versus the $6,000 furnace? There are several factors that play into the final cost.

  • Capacity/power of the system
  • Efficiency – SEER Rating
  • The HVAC equipment you’re not replacing
  • Modifications to your existing system
  • Line set protection
  • Installation costs
  • Tax credits and rebates

How To Choose The Best Furnace?

  • Energy Source – The biggest differentiator is the energy source of your furnace. To find the most cost-effective energy source, you must look up what is available in your area. For most homes in America, this will be natural gas. In remote places, it may be oil, wood, or propane. Only in extremely warm climates will electricity be the most cost-effective option.
  • Efficiency – The more you pay upfront, the lower your utility bills will be each month. A high-efficiency furnace is between $3,000 and $5,000 but will cost you less to run each month than a $1,500 -$2,000 furnace.
  • Size – The bigger the home, the more power in your furnace you need to heat it. Bigger furnaces will cost more than smaller ones. You can find the exact size of furnace you need by calling an HVAC contractor to have your home sized for a new furnace.
  • Installation – The cost of installation is separate from the cost of the furnace itself. Installing a furnace is not a DIY job, no matter how handy you are. Dealing with these volatile fuel sources is not something you can do yourself. Be sure to use a qualified HVAC contractor for your home installation.
  • Brand – You will pay more for a name brand, but they also come with a better warranty than lesser-known company brands.
  • Ongoing Costs – Before buying a furnace, consider the ongoing costs of maintenance, filters, cleaning, etc.

FAQs About Furnaces

Your carbon monoxide detectors should be at least 5-20 feet away from sources of CO such as a furnace, water heater or fireplace.

Typically, a furnace lifespan is between 15-30 years. We see most furnaces replaced around the 20 years mark.

This depends on the type of filter you buy. If you choose a filter that is less than $10, it will likely last you less than one month. Other filters may last up to a year. Thicker filters last longer. For example:

  • 1 to 2-inch filters: replace every 1 to 3 months
  • 3 to 4-inch filters: replace every 6 to 9 months
  • 5 to 6-inch filters: replace every 9 to 12 months

Furnace energy efficiency is measured by the AFUE standard or Annual Fuel Utilization Efficiency. The higher the percentage, the more efficient the furnace. The minimum AFUE required for most furnaces is 80 percent AFUE.

Get Warm and Stay Safe

A comfortable and healthy home environment requires an energy-efficient and safe furnace system. We all want to heat our homes without using large amounts of energy and having huge utility bills. Choosing the right system, maintaining it throughout the year, and replacing it when necessary are all essential to keeping your family safe and warm throughout the winter months.