Air blowing out of a return vent usually indicates a pressure imbalance in your HVAC system, likely caused by a heavily clogged air filter, leaky or disconnected return ducts, or a malfunctioning zone damper. This reversing of airflow means the system is pushing air out instead of sucking it in.
Leaky ducts are almost always why your return vents keep blasting chilly air even though you need heat. However, they're not the only cause of cold return vents. Before you call your local duct installer to inspect your ducts for leaks, you should look into these other possible causes first and rule them out.
Here are some signs of backdrafting:
Yes, you should turn the furnace off if it is continuously blowing cold air. Turning it off prevents the system from blowing unheated air, stops it from wasting electricity, and prevents further damage to the unit if there is a malfunction.
5 Warning Signs It's Time for Furnace Replacement
A standard residential furnace lasts 15 to 20 years. However, the exact lifespan varies based on the type of system and how well it is maintained.
The heat exchanger is often considered the most costly part of a furnace to repair or replace. It is a critical component that transfers heat from the combustion process to the air that circulates throughout your home. Over time, heat exchangers can crack due to the constant heating and cooling cycles they undergo.
Heating Schedules. Keep to a steady heating schedule over winter to keep a home consistently cozy. HVAC technician Josh shares, 'On average, in winter weather, most furnaces or boilers will cycle on and off for eight to 12 hours per day. That's assuming daytime temps around 35-45°F (1 to 7°C) and nights in the 20s.
It takes time for your home to warm up and cool down. If you're not sure how long it takes, try turning the heating on about 30 minutes before you need it. You should turn it off 30 minutes before you'll stop needing it.
The Furnace Won't Ignite: This is the most common and most telling sign. If the gas valve doesn't open, the ignition sequence simply can't begin. Intermittent Heating or Sudden Shutdowns: These unpredictable cycles often point to weak solenoid coils or unstable electrical connections.
A backdraft is a deadly explosion that occurs when a fire, starved of oxygen in a confined space, suddenly receives a fresh supply of air. As oxygen rushes in, superheated, unburnt combustible gases violently ignite. Recognizing the warning signs is critical for survival.
In general, you can expect your furnace to cycle (on-off) about 3 to 8 times per hour in cold weather. Several factors determine how often the furnace cycles on in winter. The key factor is the outdoor temperature and the heat loss rate of your home.
Common Signs Your Furnace May Not Be Venting Properly
If you've changed filters, cleared vents, and still notice:
A frozen pipes furnace failure can cause major problems inside your home. Ice builds up fast in unheated spaces, and when frozen water expands, it can burst pipes wide open. That kind of mess is the last thing anyone wants during a winter heating outage.
Cold air blowing from vents when your heat is on often signals a thermostat set incorrectly or a clogged air filter restricting airflow.
For most customers, we recommend turning on your furnace when the weather is consistently below 18° Celsius, which usually happens to be around the end of September, or early October. Some homeowners try to put off turning on their furnace as long as they can to save money, which is okay if you're healthy adults.
How to Stay Warm if Your Furnace Breaks
The most efficient temperature to set your thermostat, particularly for optimizing your heating and cooling system, is typically around 78 degrees Fahrenheit for cooling in summer and 68 degrees Fahrenheit for heating in winter.
What fails first on a furnace? The most common early failures are the furnace ignitor or flame sensor, as they experience regular wear and tear and are critical to starting the heating cycle.
A furnace typically lasts between 15 and 20 years. However, the exact lifespan varies based on the type of unit and how well it is maintained.
Homeowners insurance may cover the cost to repair or replace your furnace or boiler if it's damaged or destroyed by a covered peril. Covered perils as defined by your policy typically include events such as: Lightning. Fire.
The best time to buy a furnace is during the off-season, specifically late spring (April-May) or early autumn (September-October), when HVAC companies are less busy and offer lower prices, rebates, or promotions. Purchasing in these shoulder seasons ensures faster installation times and better negotiating power compared to winter peak season.
Furnaces 20 years old or older become increasingly inefficient over time and can crack and leak, putting you and your family in danger. If your furnace is between 16 and 20 years old and constantly breaking down, then you should strongly consider having it replaced.
Average Cost to Replace a Furnace
However, the cost of furnaces can range widely depending on their size, type, and efficiency, and homeowners can generally expect a new furnace to cost anywhere between $3,800 and $10,000. If efficiency is important to you, high-efficiency models can reach up to $12,000.