According to the Department of Energy, most homes in the United States are spending the bulk of their energy costs on heating. Coming in at an average of 45% of the energy bill each month, heating your home is an expensive luxury that is worth taking the time to understand a bit better.

The most common appliances for heating a home in the US are furnaces and boilers. Knowing how to maintain your furnace and watch for signs that something is wrong can do more than save you money. Heaters in need of repair by a professional cannot be ignored, as one serious problem is the leaking of carbon monoxide – a gas that is lethal in high doses.

Understanding how your furnace works, how to maintain it, and when to heed warning signs can save your pets or family member’s lives.

How it Works

Heating systems have three main components, and if something in your unit requires repair it probably has to do with one of these items:

furnace repair

  • Heat Source
  • Heat Distribution System
  • Control System

The heat source, such as a furnace or heat pump, provides the warmth needed for the rest of the house. This can be warm water or warm air, depending on the system. The distribution system then moves warm air (or water) throughout the building. The control system is another name for your thermostat and is how you set the desired temperature for a room or home.

Types of Heating Systems

Not all systems are equal, but before contacting a technician be sure to know what type of system is in your home. Furnaces and boilers are also referred to as central heating systems since the heat source is located in one spot, usually towards the middle of the building, and heat moves throughout the house from that central location.

Typical heating systems include:

  • Furnace
  • Boiler
  • Heat Pump
  • Active Solar Heating
  • Electric Heating

Types of Distribution

There are several different ways that heating systems move warmth throughout the house. No matter the appliance, all heaters distribute in one of the following ways:

  • Forced Air
  • Electric or Hot Water Baseboards
  • Direct or Steam Radiant

Furnaces use a forced air system. Through air ducts and vents, like a central air conditioning system, warm air is pushed throughout the building to heat every space. This system is good because your A/C can use the same ductwork.

Unfortunately, forcibly pushing air around also means dirt and dust get pushed throughout the house too. Allergens such as pollen and dust are moved all over your home unless the ductwork is well sealed and filters remain clean.

3 Warning Signs

While there are some things you can take care of without help, sometimes problems require the expertise of a furnace repair technician. To help you sort out the small problems from the real issues, we have put together a quick reference list of the most common problems furnaces face.


1. Thermostat Malfunction

If you find yourself in the middle of a war with the thermostat, constantly adjusting the temperature setting to stay comfortable, a few different causes could be to blame.

First, change the batteries. This easy fix could save you a call to the service pros.

If some rooms are hot while others are cold, the problem is not likely with the thermostat, but with the ductwork. Leaks in the ducts allow warm air to leach out before reaching their destination, leaving some rooms significantly colder than others.

Another note to consider is windows. Traditional pane windows do not insulate heat nearly as well as solid walls, so you could be getting extra heat in rooms that face the sun or losing heat in areas with large windows.


2. Strange Noises

The noises your furnace makes when shutting off or turning on are nothing to cause concern. The kicking on of a blower or rushing sound of air is normal.

Now, if you hear banging, popping or significant rattling sounds, there may be a bigger problem. Older heating units start to make loud noises as they approach the end of their life as a functioning furnace.

If the blower seems to continually turn on and off (which does make noise as mentioned before), you should contact a technician and look into furnace repair.


3. Pilot Light

The pilot light should remain blue at all times. When the light is yellow instead of blue, there is a severe risk of carbon monoxide (CO) production. This toxic gas can poison everyone in your home and should always be addressed by a professional. If you are concerned about carbon monoxide before the light changes color, a variety of small CO indicators are available at a low cost.

Carbon Monoxide (CO)

Incomplete combustion or blockage to air flow can lead a furnace to produce CO.

Due to its dangerous nature, here are some additional indicators that CO may be coming from your furnace. Since the gas is odorless and tasteless, you may never realize there is a problem without reading the signs.


  • For homes with chimneys, no upward draft is present
  • Soot streaks form around the furnace
  • Rusting of pipe connections or flue
  • Moisture on the walls and windows, in addition to normal condensation

Understanding Efficiency

The Department of Energy measures efficiency of heating systems in terms of AFUE (Annual Fuel Utilization Efficiency). To help understand where your furnace falls on the scale of efficiencies, here is a quick reference section.


Old System – Low Efficiency

Even though the life expectancy of a furnace is 15 – 30 years, older systems are heavy and inefficient. They often use the natural flow of air through a draft to move the combustion gasses, which drops efficiency significantly.

The pilot light must remain lit at all times and expect the unit to perform no better than 70% AFUE. Older units may operate as low as 56% AFUE.


Mid-Range Efficiency

Middle-efficiency furnaces are smaller and lighter weight than older systems. With improvements like an electronic ignition instead of a pilot light and a fan to control the flow of air, AFUE improves to 80 – 83%.


High Efficiency

The newest heating systems available have a much higher efficiency – reaching 90 – 98.5% AFUE! This is achieved through a sealed combustion system and a secondary heat exchanger.


To do a check on whether your furnace is still a good fit for your home, try ENERGY STAR’s Yardstick program. The Department of Energy and the Environmental Protection Agency use the ENERGY STAR certification program to signify to consumers products that are tested and proven to be more efficient and reduce energy costs.

heating system

Heating System Maintenance: What You Can Do

Before committing to furnace repair, there are some at-home maintenance jobs you can do on a forced air system. Make sure the unit is off anytime you open a panel!

  • 1Remove dirt, soot, and corrosion from the furnace and blower
  • 2Clean filters or replace them each month
  • 3Test for CO (at home sensors are easy to install)
  • 4Visually inspect the combustion chamber for cracks when the unit is off
  • 5Check connections between the furnace and ducts and seal if needed
  • 6Make sure vents are clear

Heating System Maintenance: What the Professional Can Do

While we applaud the DIY experts, major furnace repairs should go to the professionals. Inspection of chimneys, vents, and pipes wear out over time and repairs can be pricey. Always get a quote before doing major repairs to the system components and research your options.

The heat exchanger inspections and repairs are other tasks for the pros only. If there are leaks in the exchanger, only a professional should complete the repair.

Control settings for optimal performance are put in place by the manufacturer, and only a furnace repair tech should make adjustments.

Retrofitting vs. Replacement

Instead of replacing a heating unit, talk to your furnace repair technician about the options for upgrading or retrofitting the existing system. You may be able to have them install a programmable thermostat to keep a more constant temperature in the house. This allows your furnace to work smarter, not harder and can reduce monthly bills by 10%.

Sometimes upgrading the ductwork will improve efficiency too. A professional can provide details on what other options are cost-effective and be sure to ask during the repair process if there are ways to extend the life of your furnace. They should be capable of performing a combustion-efficiency test to help you decide what to do next.

Improving the heating and cooling efficiency of your home may extend beyond the furnace though. Installing better insulation in the attic or making sure windows properly seal against the outside elements can lead to big changes in the environment inside your home.

Time to Replace? What to Consider

furnace repair


When the time is up for your furnace and repairs are happening more than twice a year, start looking at what you need before the unit is beyond repair.


Fuel Source

Depending on where you live, resources differ and so do the most common heating systems. In the northwest part of the continental US, for instance, natural gas is accessible, and therefore gas heating systems are more cost-effective.



Living in warmer climates, where you rarely need to run the furnace for more than a few days at a time, should affect your choice of system. Space heaters may suffice or central systems provide both heat and air conditioning.



Follow the ENERGY STAR rating system and make sure the unit installed matches the needs of your home's square footage. If you live in a region where you won't run the furnace often, having an expensive high-efficiency unit for only a 10% improvement in cost may not be worth it.



Make sure the furnace isn’t too big for the space being heated. If your home does not need a large heating unit, there is no need to spend the money and efficiency doesn’t matter if the size is wrong.