Is this the Year to Replace Your Furnace?

How long do furnaces last? Manufacturer and industry recommendations are as short as 18 years. All furnaces should be replaced before 25 years.

By Rebecca Martin

October arrives in many parts of the country with thoughts of when is the right time to turn on the furnace? Hopefully, it also brings concerns regarding the furnace itself. While it is tempting to forego maintenance in October, foregoing maintenance now may lead to much more serious problems in winter and can increase the risk of danger to yourself and family members. While the furnace won’t run as long during these periods were the temperatures fluctuate, the first time you turn on the furnace may be the most dangerous. The furnace may have had several months since it was last used and things can go wrong over the summer.

How long do furnaces last? It depends to some degree based on the type, but generally between 18 and 25 years. If your furnace isn’t high efficiency, it almost certainly has to be replaced because it would have been made a very long time ago.

One of the first things you should consider as a homeowner is that while we tend to focus on the more superficial features of our homes, such as function and design, we really need to be prepared to pay as much attention to the machinery which runs our homes and budget for any repairs or replacement above all else. It is highly recommended for all homeowners to set aside 1-3% of their home’s value per year to address major repairs or replacements such as roof repairs, sewage and plumbing, appliances and HVAC. Ideally a home repair budget should have its own account and funneling funds into that account through an automatic transfer can insure that the money is there when needed. Often these repairs are in the thousands of dollars. If maintenance is deferred and something fails, it can be far more expensive to deal with an emergency when one has little time to inquire into all available solutions.

How Long do Furnaces Last May Depend on Type

There are several types of furnaces that are found in homes. Except for electric furnaces, all of them are capable of producing carbon monoxide. Carbon monoxide is a produced any time there is a fuel-burning device. So whether your furnace is gas, oil, propane or even wood; it is capable of producing carbon monoxide.

How Long do Oil Burning Furnaces Last

Oil burning furnaces can have a life expectancy of around 25 years, if and only if proper preventative and regular maintenance has been performed. The performance of oil furnaces decreases in efficiency dramatically at 15 and 20 years and outdoor tanks may only last 15-20 years before needing replacement. Neglecting the potential failure of the outside tank can lead to environmental contamination which can be a very costly problem and impact the home’s value.,than%20one%20that%20was%20neglected.

An annual maintenance check on an oil furnace will include a filter replacement, an inspection and cleaning of all the moving parts in your system, and a test for efficiency. The burner assembly should be cleaned and inspected for wear and tear. Flue pipes should be checked for rust, corrosion, and any blockages. The connections of all components; igniters, vents, filters, pumps and more should be checked. A thorough maintenance check should also include adjusting the burner for maximum efficiency.,sure%20it%27s%20free%20of%20obstructions.

How Long do Gas Burning Furnaces Last

Gas Furnaces have a wide variety of variables for life expectancy depending on the make and model, in general they last 15-20 years if maintained properly. The furnace’s life expectancy may vary due to size, how often and how long it is in operation, what temperature your thermostat is normally set at and the design of ductwork. While an annual inspection is adequate for a furnace under fifteen years old, it is recommended that furnaces over fifteen years have a bi-annual checkup to insure the most safe and efficient operation.  It is especially important for furnaces nearing the end of their anticipated life expectancy to have more frequent maintenance.

It is worthwhile mentioning that though electric furnaces are more expensive to operate, they may save you money in the long run by extending the life expectancy of your heating system with a life expectancy of 20-30 years.  Aside from avoiding costly replacement at 15 years, there also is no danger of carbon monoxide poisoning.

DIY Maintenance of Your Furnace

While annual inspections of your gas furnace are considered a necessity by all manufacturers, there are tasks you should perform regularly to keep the furnace at maximum efficiency. Filters should be changed regularly. The recommended frequency depends on your homes occupants. 90 days is the suggested lifespan of a filter in normal situations, a home with pets should have filters changed every 60 days, and if there is someone in the home with allergies, the filter should be changed every 30-45 days.

You can also inspect the gas line from the main valve on, listening for the hissing sound of leaks or the smell of gas.

You should also be familiar with the venting system and what the vents are in your home. They should be kept clear and protected from animals and debris.

Rust is a Warning of Carbon Monoxide Poisoning

The area around your outside furnace vent should be clear of any signs of soot or discoloration as well. Discoloration can indicate that there is a gas problem, and your furnace is burning too hot or isn’t getting enough oxygen for the amount of fuel that is being burned. Corrosion on any vent pipe is always a serious problem. A professional should be consulted immediately because the risk of carbon monoxide or fire is present. The air coming from the furnace exhaust pipe should be warm and never hot. PVC pipes should never show signs of extreme heat. If there is discoloration around interior air vents it could be due to mold and that should also be addressed by a professional for health reasons and to address moisture in the system. Even though one of the products of complete combustion is water vapor, a properly operating system should vent the water vapor entirely to the outdoors and when it is staying in the flue, that is a sign of things going wrong. For more on negative pressure, click here.

Carbon Monoxide Detectors are a Must

One of the most important jobs you can perform as a homeowner is to make sure carbon monoxide detectors are installed as recommended, are functioning and replaced as needed. Most carbon monoxide detectors last 5-7 years. In general, they will chirp every 60 seconds to indicate the battery needs to be replaced and every 30 seconds to indicate that it has reached the end of its useful life.

An interesting aside on the topic of carbon monoxide detectors, I recently heard of a concern amongst older users that there are certain brands of carbon monoxide detectors that have instruction manuals with print too small to read for elderly homeowners. When shopping for carbon monoxide detectors for older homeowners, it might be wise to make sure that they understand how they function or might opt to get a brand that has an instruction manual they can consult easily to understand warning sounds and light flashes. Disconnected carbon monoxide detectors are the same as having no detectors. Of course, manuals for all CO detectors should be available to download from the internet and then it can be read on your computer.

Annual Furnace Inspection

One of the most important tips I have learned about choosing HVAC professionals is to make sure whoever is doing the inspection is the same person coming to do any repairs or supervise repairs. If they send out a crew instead, you have no assurance that the subcontractors they use are as knowledgeable as the person who discovered issues and advised what solutions are available. You have every right to question the qualifications of the workers doing the job.

A commercial HVAC technician should be licensed by the state and not be hesitant to show their credentials.

Your annual inspection should include all of the following, according to Angie’s List:

  • Clean Burners
  • Check Heat Exchanger
  • Clean and Oil Motors and Bearings
  • Check Thermostat
  • Check Ignition and Flame
  • Flush Drains and Traps
  • Check Venting
  • Inspect and Clean Blower
  • Adjust and Tighten Panels
  • Check Controls and Safeties
  • Run a Combustion Analyzer to be sure if is running properly.

If the furnace fails inspection and is deemed unsafe, the inspector should shut down the furnace and inform you that the system is unsafe to operate and advise you of what actions should be taken to rectify the problem and the utility company may be contacted to further evaluate the problem.

If the system is deemed inoperable, the inspector will advise you of what corrections are needed.

There is also the issue of accessibility. The furnace must be accessible for inspection and there are very specific regulations to address furnaces in attics, crawlspaces and underfloor.

Furnaces should never be located in spaces where people sleep, in bathrooms or in storage closets. Although there are some exceptions, the concern is adequate venting and an incoming air flow from the outside.

You should also be aware that regulations and requirements for the HVAC industry change almost yearly and what was acceptable last year may not be acceptable this year. I had experience with this recently when an HVAC technician came to examine a malfunctioning water heater and because the code had changed this year it became a very large project that entailed replacing gas lines, rerouting venting and a tankless water heater as the installation could not be brought up to code to accommodate the previous type of installation.

On average, an annual furnace inspection, without repairs or problems, should cost around $100. If you consider that a replacement could cost thousands of dollars, that is a small insurance policy against furnace failure.

The biggest payoff for routine maintenance and annual inspections is the prevention of tragedy. Every winter we see numerous news stories of people sickened or who perished due to malfunctioning furnaces. Multiplying those occurrences are furnace failures which force homeowners to turn to generators and other forms of heating. I recently had an acquaintance disclose she had turned on her gas stove for heat rather than turn on her furnace for the season. Despite numerous warnings on the news media or PSAs from emergency services and firefighters, people still ignore warnings.

It is important that you have knowledge of where your air intakes and venting are located. Heavy snow and winds may block airflow during the winter and it is important that you understand placement and function.

Choosing Your HVAC Company

This is my first year in my current house, choosing an HVAC company in an area I am not familiar with seems daunting. There are guidelines, according to Forbes, on how to choose the right HVAC company. You should check any reviews on online platforms, search the Better Business Bureau website, consult multiple HVAC companies to ask about experience, availability, and rates, ask if they are familiar with your specific brand of furnace and equipment and get a written estimate for any repairs that need to be done.

When selecting an HVAC company, ask them whether their techs have combustion analyzers and whether they use them each time they fire up a furnace or other appliance after servicing them. A combustion analyser is the only way to be sure that the furnace is running a clean burn, without carbon monoxide in the exhaust.

If you haven’t had your annual inspection this year, now is the time to schedule. If you are a renter, it would also be a good time to ask your landlord if an annual inspection has been done. Be aware that often rental properties are serviced by a contractor who may perform only the minimum inspection and maintenance. As a renter, your greatest defense against shoddy HVAC maintenance is to make sure you have carbon monoxide detectors and depending on your rental contract, you may be required to maintain and replace those as necessary.


October is also a great time to make sure that all woodburning devices are serviced as well before lighting that first fire of the season.

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