Protecting Your HVAC From Snow, Ice and the Polar Vortex

Every few winters, a polar vortex pushes arctic air into Chicago and temperatures stay below zero for days. Even ordinary winters bring heavy snow, freezing rain and long cold stretches. During those events, heating systems run almost constantly, and small problems become no-heat emergencies. HVAC companies are overwhelmed, and response times stretch.

This guide covers how to prepare your heating system before extreme weather, what to watch during storms and cold snaps, and what to do if your heat fails.

Before Winter: Lay the Groundwork

Schedule Fall Service

A professional tune-up before winter is the single best defense. It catches weak ignitors, dirty flame sensors, failing motors, venting problems and safety issues while the weather is mild. Our fall furnace checklist explains what to do and what a technician should check.

Stock Up on Filters and Batteries

Keep spare filters, thermostat batteries and flashlight batteries on hand. A clogged filter during a cold snap can overheat the furnace and shut it down.

Know Your Shutoffs and Numbers

Know where the furnace or boiler service switch, breaker and gas shutoff are. Keep your HVAC company's number and the Peoples Gas emergency line, 866-556-6002, where you can find them quickly.

Test Carbon Monoxide Alarms

During extreme cold, furnaces and boilers run longer, windows stay closed and people sometimes use unsafe heat sources. Make sure CO alarms are working near bedrooms and on every level. See our carbon monoxide safety guide.

Keep Vent Pipes Clear

High-efficiency furnaces and many modern boilers and water heaters vent through PVC pipes that exit the side of the house, sometimes close to the ground. Snow drifts, plowed snow and ice can block them. When the intake or exhaust is blocked, the appliance's safety switch usually shuts it down. If exhaust cannot escape, there can also be a carbon monoxide risk.

• Know where your vent terminations are before the first snow.
• After heavy snow or drifting, check that both pipes are clear.
• Clear snow gently by hand or with a brush. Do not use tools that could crack the pipe.
• Watch for ice buildup at the exhaust, which can form when warm, moist exhaust freezes in extreme cold.
• Do not pile shoveled snow near vent pipes.

If vent terminations are too close to the ground and get buried often, ask a technician about raising them within code and manufacturer requirements.

Protect Heat Pump Outdoor Units

• Clear snow from around the base and sides so air can flow, and keep the top uncovered.
• Make sure gutters and roof edges are not dripping onto the unit, which can encase it in ice.
• Do not chip ice off the coil with tools. If the unit is encased in ice, switch to emergency heat if available and call for service.
• Expect defrost cycles with steam. That is normal. See our guide on heat pump defrost mode.

Watch for Frozen Condensate Lines

High-efficiency furnaces produce condensate water that drains away through a trap and tubing. If the line runs outside, through an unheated garage or near a cold exterior wall, it can freeze during extreme cold. A frozen line backs water into the furnace and triggers a safety shutdown.

Signs include water around the furnace and an error code for a pressure switch or drainage fault. Protecting lines that pass through cold spaces with insulation or heat tape installed by a professional, and routing them to indoor drains, prevents most problems.

Keep the Thermostat Steady in Extreme Cold

Setbacks save energy in normal winter weather, but during extreme cold, large overnight setbacks can backfire. Recovery runs are long when the furnace is already near its limit, and the house may never catch up on the coldest mornings. For heat pumps, large setbacks can trigger expensive backup heat. During a polar vortex, keep the thermostat at a steady, reasonable setting. Our guide on thermostat settings for Chicago winters covers this in more detail.

Prevent Frozen Pipes

• Keep the thermostat high enough day and night. Never turn heat off.
• Open cabinet doors under sinks on exterior walls so warm air reaches pipes.
• Let faucets on exterior walls drip slightly during extreme cold.
• Keep garage doors closed if water lines run through the garage.
• Insulate exposed pipes in basements, crawlspaces and attics.
• Seal drafts near pipes, especially at the rim joist in basements.

In homes with boilers, heating pipes and radiators in cold spaces can also freeze if the boiler fails. If your boiler stops during a cold snap, call for service immediately.

Know the Warning Signs During a Cold Snap

• The house temperature drops below the setting and keeps falling.
• The furnace or boiler cycles on and off frequently.
• The furnace runs but blows cool air.
• New noises, such as banging, squealing or grinding.
• Error codes on the furnace or boiler display.
• Water around a high-efficiency furnace.
• A heat pump encased in ice.

Act early. A technician is easier to reach for a struggling system than after a complete failure. Our guides on furnace short cycling and furnace blowing cold air cover common cold-snap problems.

Power Outages and Generators

Gas furnaces and most boilers still need electricity for their controls, ignitors, inducers, pumps and blowers. During a power outage, they usually will not run. If you use a portable generator:

• Run it only outdoors, far from windows, doors and vents. Never in a garage, basement or porch.
• Have a qualified electrician install a proper transfer switch or interlock if you want to power the furnace. Never backfeed through an outlet.
• Make sure CO alarms have battery backup.

If Your Heat Goes Out

• Check the thermostat, the furnace switch and the breaker.
• Replace a dirty filter.
• Check outdoor vent pipes for snow or ice.
• Look for an error code and write it down.
• Try one reset. Do not keep resetting a system that locks out.
• Call for emergency HVAC service.

While you wait, gather in the warmest room, close off unused rooms, use only safe heat sources and protect pipes. Never use a gas oven, stovetop, grill or outdoor heater to heat your home. Our detailed guide on what to do when your heat goes out in a polar vortex has a full checklist.

For Landlords

Chicago's heat ordinance requires landlords to provide minimum indoor temperatures from September 15 through June 1, including 68 degrees during the day and 66 degrees overnight in most residential buildings. Extreme cold is when heating systems in older multi-unit buildings are most likely to fail. Fall service, a plan for emergency repairs and clear tenant communication are essential.

After the Cold Snap

Once temperatures return to normal, check the filter, look for water around equipment, check pipes for leaks from freezing and note any problems the system had. If the system struggled, schedule a service visit to find out why before the next cold wave.

Ice Dams and Your HVAC

Ice dams form when heat escaping into the attic melts snow on the roof, and the water refreezes at the cold eaves. Besides damaging roofs and gutters, ice dams can drop heavy ice onto outdoor HVAC units, bend fins and crush fan grilles, and send meltwater down onto heat pumps. Improving attic insulation and air sealing reduces ice dams. Make sure no heating ducts in the attic are leaking warm air, which can make ice dams worse.

Boiler Systems in Extreme Cold

Boilers face their own cold-weather issues. Hot water systems can lose pressure through small leaks, and steam systems can run low on water during long run times. Check the pressure gauge or sight glass regularly during a cold snap. Radiator pipes running through cold spaces, such as unheated porches or along exterior walls, can freeze if the boiler fails. Our guide on boiler on but no heat covers what to check.

Commercial and Mixed-Use Buildings

Many Chicago neighborhoods have storefronts with apartments above. Rooftop units and shared mechanical rooms in these buildings need the same winter attention: clear vents, protected condensate lines, accessible equipment and a plan for after-hours emergencies. Coordinate with tenants about who to call if heat fails overnight or on weekends.

Build a Simple Winter Kit

• Spare furnace filters.
• Thermostat and flashlight batteries.
• A snow brush for clearing vents and outdoor units.
• Pipe insulation and towels.
• Blankets and warm clothing.
• A battery-powered CO alarm.
• Phone numbers for your HVAC company and Peoples Gas.

Checking on Neighbors and Vulnerable Family Members

Extreme cold is dangerous for older adults, infants and people with health conditions, especially if heat fails. During a polar vortex, check on neighbors and relatives who live alone. Make sure they know who to call if their heat stops, and that they have working CO alarms and a safe way to stay warm. The City of Chicago opens warming centers during extreme cold, and calling 311 can connect people with help.

Insurance and Documentation

If extreme cold damages your property, such as frozen and burst pipes, take photos, keep records of repairs and contact your insurer promptly. Keeping records of regular heating system maintenance can be helpful if questions arise about whether damage was preventable.

Quick Polar Vortex Checklist

• Fresh filter in place.
• Outdoor vent pipes and heat pump clear of snow and ice.
• Thermostat at a steady, moderate setting.
• Cabinet doors open under sinks on exterior walls.
• CO alarms tested and working.
• HVAC company and Peoples Gas numbers handy.
• A plan for keeping everyone warm safely if the heat fails.

A few minutes of preparation before the arctic air arrives can prevent a long, cold night and expensive repairs.

Get Ready Before the Next Polar Vortex

Call (312) 638-0812 to schedule winter service, or if your heat is struggling now. We serve neighborhoods including Logan Square, West Ridge and Norwood Park. Learn more about furnace repair, boiler repair and tune-ups.