Knowing how to tell when your aging furnace has reached the end of its life can be difficult, but the last thing you want is to find out in the middle of winter when heating your home is a necessity. If your furnace is 10 years old or older, you need to start monitoring it to evaluate whether or not it has passed its best-before date.

Here are some other things to watch for that could be signs you need a new heating system:

Your Heating Bill Increases

If your heating bill unexpectedly rises, it could be a warning sign that your furnace needs maintenance. A sudden spike in your heating bill could foreshadow the need for a new furnace. Analyze your heating bills from previous months to see if there are any discrepancies with your current bill. Be sure to look closely at the amount of energy your furnace is using as opposed to the variance in dollar amounts between bills. If your bill is rising but the rate of energy usage hasn't changed, that suggests your furnace's energy efficiency is no longer what it used to be.

Your Home Is Dry or Dusty

When your heating system is nearing the end of its life, it becomes harder for it to keep the air moisturized and clean. In the winter, the air is as dry as it is cold. Are you or a family member suffering from dry skin or sinuses? It may be because the air in your home is extremely dry. There are a few reasons for this. Your home's humidifier may be set too low or it's on the fritz, or air leaks in your home are allowing warm, humid air to escape.

Older furnaces generally use air in your home for combustion. This process generally dries the air in your home because it creates a vacuum in the home’s envelope, sucking dry air from outdoors inside under doors and through cracks and crevices around windows or in the building’s structure. A modern furnace uses outdoor air for combustion and allows the home to better maintain its humidity level inside.

If you're noticing an increase in the amount of dust settling throughout your home on furniture or clinging to the walls, it may indicate your home's air purifier is not working properly, or it may be time for a new heating system.

Uneven Temperatures Throughout Your Home

If heat is being distributed unevenly throughout your home, that too is a sign something isn't right with your heating and ventilation system. The temperature from room to room should be the same. If it isn't it could mean your aging furnace is struggling to maintain the right balance of temperature, that your ventilation ducts need to be cleaned, that your home's windows and doors need to be re-sealed, or all of the above.

You’re Hearing Strange Noises Downstairs

Older furnaces often make noises. That isn't always a bad sign, however, it's important to be aware of these noises and to take notice when you hear a new or unfamiliar one. Banging, squeaking, rattling and other noises can all be signs your furnace is nearing the end of its service life. Is your furnace's blower operating sporadically? If it's turning on and off frequently, or blowing cool or cold air, it's time to call in a professional to inspect your furnace and blower motor.

There Are Visible Signs of Rust

If you see rust on any parts of your furnace or the floor around it, it may be because of corrosion inside the furnace. This could mean that your furnace is working a lot harder than normal to heat your home. In other words, rust is not a good sign.

Your Furnace Flame Is Yellow

While checking your furnace for rust and corrosion, it's also a good opportunity to check the colour of the flame. If the flame isn't blue and appears yellow, this could mean it's producing deadly carbon monoxide. If this is the case, leave your home immediately and call a professional right away.

Your Furnace Has Been Repaired Several Times

If your furnace needs more than just wear-and-tear maintenance consistently, you may want to consider purchasing a new one -- especially if you're paying for the same repair repeatedly. It may seem like a large investment, but it will save you money in the long run.

Although all of the above can be telltale signs you need a new furnace, it's also possible your system simply needs a tune-up. Regardless, it's wise to have a professional technician inspect your heating, cooling, and ventilation (HVAC) system annually. It's important to remember, that the health and condition of your home's HVAC system directly impacts the value of your home and property, as well as your family's health.