How to Winterize a House: Colorado Cold-Weather Checklist

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Front Range winters are unpredictable. A sunny 60-degree afternoon can be followed by a night in the single digits, and the first hard freeze often arrives in October, well before many homeowners have thought about the cold. That swing is exactly what bursts irrigation lines, splits outdoor faucets and builds ice dams on roofs. Taking a few weekends in early fall to winterize a house protects the plumbing, the heating system and the roof, and it lowers the risk of a mid-winter emergency. This checklist covers the outdoor water system, the furnace and filters, gutters and ice dams, attic air sealing and insulation, smoke and carbon monoxide alarms, special steps for vacant or second homes, and preparing for power outages. Cost figures are broad industry estimates, not quotes, and local prices vary.

Part of our Structure & Exterior guide — start there for the full picture →

Winterize House Checklist: The Short Version

If you only have one afternoon, start with the items most likely to prevent expensive damage:

1. Have the sprinkler system blown out and shut off.
2. Disconnect garden hoses and protect outdoor faucets.
3. Replace the furnace filter and schedule a heating tune-up.
4. Clean gutters and make sure downspouts carry water away from the house.
5. Test smoke and carbon monoxide alarms.
6. Locate the main water shutoff and make sure it works.
7. Seal obvious drafts around doors, windows and attic hatches.

The sections below explain each step and the less obvious items that matter in a Colorado climate.

Outdoor Water: Sprinklers, Hose Bibs and Exposed Pipes

Sprinkler System Blowout

Underground irrigation systems are one of the most common freeze casualties along the Front Range. Water left in the lines, valves and especially the backflow preventer can freeze and crack them. Many homeowners schedule a compressed-air blowout in late September or October. The service typically involves shutting off the irrigation supply, draining the backflow device and pushing air through each zone until only mist comes out of the heads.

Blowouts can be done DIY with a large compressor, but too much pressure can damage fittings and heads, and the backflow preventer should be handled carefully. Many homeowners find a professional service call worth the modest cost. As a rough estimate, a residential blowout often costs somewhere around $60 to $150, depending on the number of zones and the company.

Hose Bibs and Outdoor Faucets

• Disconnect hoses. A hose left attached traps water in the faucet, which can split even a frost-free hose bib.
• Shut off and drain older faucets. Some older homes have a separate interior shutoff valve for each outdoor faucet. Close it, then open the outside faucet to drain the line.
• Consider faucet covers. Insulated foam covers are inexpensive and add a layer of protection.
• Check frost-free bibs. They should be installed with a slight downward slope so they drain. A bib that drips inside the wall after use may already be damaged.

Exposed and Vulnerable Pipes

Pipes in crawl spaces, garages, exterior walls and unheated basements are most at risk. Pipe insulation, sealing gaps where cold air enters, and keeping the garage door closed help. On very cold nights, opening cabinet doors under sinks on exterior walls lets warm air reach the pipes. Our guide to frozen pipes explains how to prevent freezing and what to do if a line freezes, and the companion guide on burst pipe repair covers first steps if one breaks.

Every adult in the house should know where the main water shutoff is and how to close it. A stuck or corroded valve is worth having a plumber replace before winter, not during a flood.

Heating System: Furnace Tune-Up and Filters

The furnace or boiler is the single most important system in a Colorado winter. A professional tune-up before the heating season typically includes checking burners and ignition, inspecting the heat exchanger area that is visible, testing safety controls, checking the flue and venting, and measuring airflow. The U.S. Fire Administration advises having heating equipment and chimneys cleaned and inspected each year by a professional.

Our furnace inspection guide explains what a technician checks and the warning signs that call for service sooner, such as short cycling, yellow burner flames, soot around the furnace, unusual smells or a system that struggles to keep up.

Filters

A clogged filter restricts airflow, makes the system work harder and can cause overheating and shutdowns. Check the filter monthly during the heating season and replace it as the manufacturer recommends. One-inch filters often need replacement every one to three months; thicker media filters last longer. Write the size on the furnace cabinet so the right replacement is easy to buy.

Other Heating Checks

• Clear the furnace area. Keep storage, paint cans and laundry away from the furnace and water heater.
• Check exterior vents. High-efficiency furnaces vent through PVC pipes on the side of the house. Snow drifts and ice can block them, which may shut the furnace down. Keep them clear after storms.
• Fireplaces and wood stoves. Have the chimney inspected and swept as needed. USFA advises keeping anything that can burn at least 3 feet from heat sources, including fireplaces, wood stoves, radiators and space heaters.
• Space heaters. Turn them off when leaving the room or going to bed, and never use an oven to heat a home.
• Thermostat. A programmable or smart thermostat can lower heating costs, and some models send alerts when indoor temperature drops, which is useful for second homes.

Roof, Gutters and Ice Dams

Colorado’s freeze-thaw cycles make ice dams a recurring problem on many homes. Snow melts on the warm upper roof, runs down and refreezes at the cold eaves, and the trapped water can back up under shingles and into walls and ceilings.

• Clean gutters after most leaves have fallen. Clogged gutters hold water that freezes and adds weight and ice at the roof edge. Our gutter cleaning guide covers safe methods and typical costs.
• Extend downspouts so meltwater discharges several feet from the foundation, and make sure the extensions will not create an ice sheet on a walkway.
• Look at the roof from the ground for missing or lifted shingles, damaged flashing and sagging gutters.
• Trim overhanging branches that could break under heavy snow.
• Plan for snow removal on low-slope sections. A roof rake used from the ground can reduce snow load at the eaves; climbing onto an icy roof is dangerous.

Heat cables can reduce damming in problem spots, but the long-term fix is usually keeping the attic cold. Our guide to ice dams explains why they form and which fixes last.

Attic Insulation and Air Sealing

Air leaks and thin insulation waste heat, and that heat warms the roof deck and feeds ice dams. ENERGY STAR notes that sealing air leaks and adding insulation can make a home more comfortable and energy efficient and provide up to a 10% savings on annual energy bills. It describes simple fixes such as weatherstripping doors and caulking around windows, and bigger jobs such as sealing leaks and adding insulation in the attic.

Common air-sealing targets before winter:

• Attic hatch or pull-down stairs: add weatherstripping and an insulated cover.
• Plumbing and wiring penetrations into the attic.
• Recessed light fixtures below an attic, where appropriate products are rated for contact with insulation.
• Exterior doors: replace worn weatherstripping and door sweeps.
• Windows: caulk exterior gaps and consider plastic window film on drafty older windows.
• Rim joists in basements and crawl spaces, a common source of cold drafts.

Insulation levels are best checked in the attic itself. If you can see the tops of the ceiling joists, there is probably not enough. Our attic insulation guide covers types, R-values and costs. Air sealing should generally come before adding insulation, because insulation alone does not stop air movement. Gas appliances in a tighter house need proper combustion air and venting, which is another reason to have a heating professional involved when making significant air-sealing changes.

Smoke and Carbon Monoxide Alarms

Winter is when homes are closed up and fuel-burning appliances run the most, so it is the right season to check alarms.

• Test every alarm using its test button, and replace batteries as needed.
• Check the date. The U.S. Fire Administration notes smoke alarms need to be replaced 10 years from the manufacture date.
• Smoke alarm placement: USFA recommends alarms in every bedroom, outside each separate sleeping area, and on every level including the basement. See our guide to smoke detector placement for details.
• Carbon monoxide alarms: CPSC advises installing battery-operated CO alarms or alarms with battery backup on every level of the home and outside sleeping areas, and notes that interconnected alarms are best.

Know the warning signs. CPSC lists symptoms of carbon monoxide poisoning including headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion, and advises getting outside to fresh air immediately and then calling 911 if poisoning is suspected.

Indoor Humidity, Condensation and the Water Heater

Colorado air is dry, and winter makes it drier. Some homeowners run humidifiers for comfort, but too much indoor humidity on cold days can condense on windows, inside exterior walls and on the underside of the roof deck. Persistent condensation on window glass, water pooling on sills or frost on attic nails are signs the balance is off.

• Watch the windows. Light fogging at the bottom of the glass on the coldest mornings is common. Streams of water, or mold on frames and sills, suggest humidity is too high or the windows need attention.
• Use exhaust fans. Run bathroom fans during and after showers and the kitchen hood while cooking, and make sure the fans vent outdoors rather than into the attic.
• Set humidifiers conservatively. Follow the manufacturer’s guidance, and lower the setting as outdoor temperatures drop.

The water heater works harder in winter because incoming water is colder. Before the season starts, look for rust or water at the base of the tank, check that the area around a gas unit is clear, and make sure the vent pipe is intact and properly connected. Many manufacturers recommend flushing sediment periodically, which can help efficiency in areas with hard water.

Exterior Surfaces, Walkways and Foundation Drainage

Snow and ice create slip hazards and can damage hardscape and the foundation over time.

• Seal or repair cracks in driveways and walkways before winter, since water that enters cracks expands when it freezes and widens them.
• Choose deicers carefully. Some deicing products can damage new concrete, plants and pet paws. Sand or traction grit is an alternative on steps.
• Check grading so melting snow drains away from the house rather than toward basement walls and window wells.
• Close foundation and crawl space vents where the home’s design calls for it, and make sure crawl space access doors seal.
• Stock supplies early: a working snow shovel, ice melt and a roof rake are hard to find after the first big storm.

Vacant Homes and Second Homes

Mountain cabins, rental properties between tenants and homes on the market are especially vulnerable because a small leak can run for days or weeks before anyone notices. Common precautions include:

• Keep the heat on. Many plumbers and insurers commonly suggest keeping the thermostat no lower than about 55°F in an unoccupied house, but check your policy and the home’s specific risks.
• Shut off the main water when the home will be empty for an extended period, and consider draining the lines. Fully winterizing a plumbing system, including blowing out lines and adding antifreeze to traps, is often done by a plumber.
• Turn off or set the water heater to vacation mode if the water is shut off, following the manufacturer’s instructions.
• Install leak and temperature sensors that send alerts to a phone.
• Arrange regular check-ins by a neighbor or property manager.
• Review insurance vacancy clauses, since some policies limit coverage after a home is unoccupied for a set period.

Buyers closing on a home in winter should ask whether the property was winterized, and whether the water has been turned back on and tested before the inspection. A home inspection cannot fully evaluate a plumbing system that is shut off and drained.

Power Outages and Emergency Supplies

Winter storms and high winds can knock out power along the Front Range, sometimes for extended periods. Preparation helps:

• Keep flashlights, spare batteries, blankets, water, nonperishable food and any necessary medications on hand.
• Keep phones and a battery pack charged before storms.
• Know how to open a garage door manually.
• Keep vehicle fuel tanks reasonably full in case travel becomes necessary.

Generators require care. CPSC warns never to use portable generators inside homes or garages, even with doors and windows open, and advises using them outside only, at least 20 feet from the home with the exhaust facing away. Never use a grill, camp stove or charcoal indoors for heat or cooking.

Typical Winterization Costs

These are rough industry estimates for context only:

• Sprinkler blowout: often around $60 to $150.
• Furnace tune-up: commonly around $100 to $250.
• Furnace filters: roughly a few dollars to $40 or more each, depending on type and size.
• Gutter cleaning: often a few hundred dollars for a typical single-family home.
• Wi-Fi leak and temperature sensors: often roughly $20 to $60 per sensor, plus any hub.
• Plumber to fully winterize a vacant home: commonly a few hundred dollars, depending on the size of the system.
• Weatherstripping, caulk and faucet covers: often under $100 in DIY materials.
• Attic air sealing and insulation: commonly ranges from several hundred to a few thousand dollars.
• Smoke and CO alarms: USFA lists ionization and photoelectric smoke alarms from about $6 and dual-sensor models from about $24; CO alarms vary.

Compared with the cost of a burst pipe or ice dam leak, most of these are modest.

References

• Seal and Insulate with ENERGY STAR — ENERGY STAR (U.S. EPA)
• Heating Fire Safety — U.S. Fire Administration
• Smoke Alarms — U.S. Fire Administration
• Carbon Monoxide Information Center — U.S. Consumer Product Safety Commission

Buying a home this winter, or not sure whether your furnace, attic and plumbing are ready for the cold? Talk to us and we can help you find a Front Range inspector to check the systems that matter most before the first deep freeze.