Is my furnace dying?

We’ve all heard the terrible tales about the home furnace that breaks down at the worst possible time, whether it's right before a holiday party or just as a cold snap sets in. 

Rather than keeping your home warm and cozy, a furnace on its last legs will not just leave you cold, and stressed out, but also paying more in monthly utility bills. And if your furnace fails during a cold snap, it’s not just a matter of wearing your parka to bed; your home pipes could freeze and burst while you wait for emergency HVAC service, leaving you with serious damage and a host of additional repair bills.

In this article, we’ll go over common warning signs that can help you figure out whether it’s time to replace your furnace. And if your furnace is no longer capable of safely, comfortably, and efficiently heating your home, we can help you weigh your options when it comes to replacing your heat source.

Your furnace is the workhorse of your forced air home heating system. Most furnaces generate heat through combustion—by burning natural gas, oil, or propane. A blower pulls cold air into the furnace’s heat exchanger and moves the warmed air around your home through ductwork, while exhaust gasses are vented outside. Some furnaces generate heat through electricity.

In this case, air is warmed as it passes over electric coils (much like how your blow dryer works), and then sent out through the ducts. One benefit to an electric furnace is that there are no dangerous emissions to worry about.

If your furnace is on the way out, it may not be able to keep your home at a consistent, comfortable temperature. While this is inconvenient when temperatures are mild, it can be dangerous for you and your family if outdoor temperatures fall below freezing. 

It’s also likely that a failing furnace isn’t working efficiently and is struggling to keep up with demand, which can cause additional wear and tear on mechanical components, as well as leave you with a nasty surprise on your utility bill at the end of the month.

If you have a combustion furnace, you should be especially attuned to any signs that your system isn’t functioning optimally. Furnaces that burn fossil fuels produce carbon monoxide as a byproduct. When your heating system is working properly, these are safely exhausted outside your home.

But some problems, like cracks or leaks in the heat exchanger, can allow life-threatening levels of carbon monoxide to build up in your home. Make sure you have a working carbon monoxide detector and be on the lookout for any signs of failure.

Formerly cozy rooms are chilly, and you’re constantly pushing up the thermostat

Likely the first sign that your furnace needs attention is when you notice it’s no longer performing like it once was. Uneven heating, cold spots around the house, or simply the inability of your system to maintain a comfortable temperature can all be signs that your furnace is no longer working efficiently. If you have the indoor shivers – and not just because you’re being conservative with the thermostat settings – take it as a sign to call  an HVAC professional to inspect your system.

Unusually high heating bills

If your area didn’t experience a historic cold snap, but your gas or electric bill is through the roof, it may be a sign that your furnace is consuming more and more energy just to produce the same amount of heat. A newer unit may only need a tune-up, but if your unit is approaching 20 years of age, you’re probably due for a replacement. 

While some repairs and retrofits can shore up older systems, the Department of Energy advises homeowners to carefully weigh these costs against the cost of a new heat source. If your monthly energy bill is a concern, a new, high-efficiency unit may be in order.

While older furnaces ranged between 56% and 70% efficiency, newer units can convert nearly all the energy they consume (up to 98.5%) into heat.

Loud or worrisome operating noises

If your furnace goes bump in the night, or if you notice a growing chorus of squealing, grinding, or popping sounds whenever it’s running, it’s also a sign to call in the professionals.

Like high heating bills, this can signal that your unit is working under stress. A timely tune-up or repair could save a newer furnace from additional mechanical wear and tear, but noises from an older furnace probably mean it’s time to consider replacement options.

Excessive moisture and rusting

Some of the most subtle warning signs that your furnace is dying are also the most important to heed. If you notice excessive condensation on your windows, moisture buildup on your walls or ceilings, and/or rusting around your furnace, flue, or vent pipes, then you need to ensure your carbon monoxide detector is in good working order and have your furnace inspected. Moisture and rusting may indicate that exhaustion gasses are not being safely vented. If you have a gas-powered furnace, a yellow as opposed to steady blue flame can also indicate ventilation issues.

Replacing a major appliance is no homeowner’s idea of a good time, but if your furnace is over 15 years old and you’ve noticed any of the above signs, it’s time to start weighing your options for replacing it– or run the risk of an ill-timed breakdown.

The silver lining here is that new heat sources compatible with your home’s existing ductwork are safer and more efficient than ever. According to the Department of Energy, replacing an aging fossil fuel furnace with a new, high-efficiency heating system could cut your monthly utility bill and your annual emissions in half.

The two main heat source options compatible with a forced air heating system are a new, mid- or high-efficiency furnace or an air source heat pump.

Compare the installation costs, efficiency, maintenance requirements, and expected lifespans between the two.