Extreme Cold and Your Home's Heating System

A deep freeze tests every part of your heating system. Equipment that handles a normal winter day can struggle when temperatures plunge and stay low for days. Knowing what's normal, what isn't, and what to do if the heat fails can help you get through a cold snap safely.

Why extreme cold is so hard on heating systems

Every home loses heat to the outdoors, and the colder it gets, the faster that heat escapes. Most heating systems are sized for typical cold weather in your area, not for the rare record low. During extreme cold:

• Systems may run almost nonstop
• Indoor temperatures may fall a few degrees below your setting
• Weak parts that got by all winter may finally fail
• Service companies get very busy, so wait times can grow

Running constantly is not always a sign of trouble. It can simply mean the system is working as hard as it can.

Furnaces in a cold snap

Gas and oil furnaces usually keep up well, but watch for:

• Short cycling, where the burner turns on and off quickly. A dirty filter or a flame sensor problem are common causes.
• Blowing cool air for long stretches, which could mean an ignition or flame problem.
• Blocked intake or exhaust vents. High-efficiency furnaces often vent through plastic pipes on a side wall. Snow drifts and ice can block them and shut the furnace down. Keep them clear.
• Frozen condensate lines on high-efficiency units, which can also cause shutdowns.

Heat pumps in extreme cold

Heat pumps move heat from outdoor air into your home. As temperatures drop, they have less heat to work with. Many newer cold-climate models perform well in low temperatures, but in a severe freeze many systems rely on backup heat, often electric heat strips or a furnace.

Things that are normal:

• Defrost cycles, where the outdoor unit may steam and the fan stops briefly
• Backup or "aux" heat turning on more often
• Higher electric bills during the cold snap

Things to check:

• Ice building up heavily on the outdoor unit that doesn't clear after defrost
• Snow or ice blocking the outdoor unit
• Backup heat that never seems to come on when the house is getting cold

Avoid big thermostat setbacks during extreme cold. Raising the temperature a lot at once can trigger expensive backup heat.

Boilers and radiant systems

Boilers are generally steady in cold weather, but watch for low system pressure, cold radiators, and condensate or venting issues on high-efficiency models. Make sure rooms with radiators or baseboards on exterior walls aren't closed off, since pipes in unheated rooms can freeze.

Simple steps to help your system

1. Replace or check the air filter.
2. Keep all supply and return vents open and clear.
3. Clear snow from outdoor units and vent pipes.
4. Close curtains at night and open them on sunny days.
5. Keep the thermostat at a steady setting.
6. Seal obvious drafts with towels or weatherstripping.

If your heat goes out

Act calmly and quickly:

1. Check the basics. Thermostat setting and batteries, the breaker, the furnace power switch, and the filter.
2. Look for error codes on the furnace or boiler control board, often shown by a blinking light.
3. Check vents for snow or ice blockage.
4. Call for service if the basics don't solve it. If you have a home warranty, call the provider's claim line first, as most plans require you to go through them.
5. Protect your pipes. Open cabinet doors under sinks and let faucets drip.
6. Stay safe. Use space heaters carefully and never use a gas oven, grill or generator indoors for heat. Keep carbon monoxide detectors working.

If you smell gas, leave the home and call your gas utility from outside.

How home warranties handle cold-weather breakdowns

Many home warranty plans cover furnaces, boilers and heat pumps under heating coverage, and some cover ductwork as well. Coverage usually applies to mechanical failures from normal use. Common limits include caps, exclusions for damage from lack of maintenance, and code upgrade limits. Some plans treat no-heat calls as priority service, but response times vary, especially during widespread cold. Check your plan's terms and review the claims process before winter.

How Warranty Wizards can help

We help homeowners compare home warranty plans from independent third-party providers and explain what each plan covers for heating systems before you buy. Get a free quote at get a quote.