How to prep your HVAC for a Front Range winter: the technician's checklist

A Colorado winter puts three things on your HVAC that most other climates don't: long heating-season hours (October through April, sometimes May at 6,200+ feet), unusually dry indoor air (single-digit outdoor humidity, driving indoor RH below 20 % without humidification), and cold snaps that swing 40 °F in 12 hours and demand peak performance the moment the wind shifts. The good news: twenty minutes of homeowner prep in September and October — followed by an actual technician-run tune-up — prevents most of the emergency service calls that fill up Colorado Bear's January phone.

Here's the checklist we'd walk a new Castle Rock neighbor through the first fall in the house.

The 20-minute homeowner walkthrough (September – October)

1 · Test the carbon-monoxide detector

This is the single most important pre-winter task, and it takes 30 seconds. Press the test button on each CO detector in your home; replace batteries or the entire unit if it doesn't sound. CO detectors have a 5 – 10 year service life — the sensing element degrades over time, and a detector that responds to the test button may still be blind to actual CO. If yours is older than 7 years, replace it regardless of how it responds. Detector plus mount runs $30 – $60 per unit. It's the cheapest safety upgrade in your home.

Colorado is a state where gas heat is dominant and cold snaps drive furnaces hard for weeks at a time — the specific conditions where a cracked heat exchanger or a plugged flue can produce dangerous indoor CO. Working detectors are non-negotiable.

2 · Replace the filter

Fresh MERV 11 or MERV 13 in the return-air grille on October 1. Note the date in Sharpie on the filter frame; check again December 1, and replace if loaded or discolored. Colorado winter air pulls indoor humidity down, which reduces filter loading rate somewhat — but you should still be on a 60 – 90 day change cadence through the heating season.

Filter selection: MERV 13 is the practical residential target unless your system was designed for higher (dedicated media cabinet with a MERV 16 filter). MERV 8 or lower is fine for basic dust filtration but doesn't protect against smaller particulates. See wildfire smoke and MERV for the full filter-choice walkthrough.

3 · Walk the outdoor unit (heat pump or AC)

Clear 24 inches of space in every direction around the outdoor condenser. Sweep out leaves, prune back shrubs, and confirm nothing has fallen against the unit. Snow accumulation is the enemy of heat pumps — the unit needs air across the outdoor coil, and drifted snow blocks that airflow. If you have a heat pump, verify the unit is elevated on a pad above expected snow depth (typically 6 – 12 inches above grade).

Do not cover the outdoor unit with a tarp or fitted cover during winter. Modern heat pumps and ACs are designed to operate outdoors year-round; covering them traps moisture, encourages rodent nesting, and (on heat pumps) prevents the unit from running when it needs to. If leaves falling on the top are your specific concern, a purpose-designed condenser top cover (fitted only to the fan grille) is fine — full-unit tarps are not.

4 · Check the humidifier

If you have a whole-home humidifier (bypass, fan-powered, or steam type):

• Confirm the water shut-off valve is open (many homeowners close it in April; check that it was reopened).
• Replace the humidifier pad or evaporator panel — one-per-season cadence is normal.
• Verify the drain line is not clogged (blow gently into the drain outlet; you should feel no back-pressure).
• Set the humidistat setpoint to 35 – 40 % RH for outdoor temps above 25 °F; step down to 25 – 30 % for colder periods to avoid window condensation.

For the humidification target math, see winter humidification in Castle Rock. Right target avoids the two failure modes: too dry (static electricity, dry sinuses, hardwood floor gaps) or too wet (window condensation, mold risk in wall cavities).

5 · Set the thermostat schedule

For a variable-speed or modulating system: minimal setback. A 4 – 6 °F night setback is fine; a 15 °F setback often costs more in recovery time than it saves. For a single-stage system: larger setbacks (8 – 12 °F) can save meaningfully, but pre-heat before the coldest morning hours. If you have a smart thermostat (Nest, Ecobee, Daikin One+), use its adaptive-recovery feature so the system starts warming the house before the setpoint time, not after.

Fan setting: "auto" is fine for cooling; "circulate" mode with the MERV 13 filter keeps air moving during heating cycles and helps balance temperatures room-to-room.

The professional tune-up (booking window: September – October)

Twenty minutes of homeowner walkthrough is not the same as a technician-run tune-up. The tune-up covers the mechanical items you can't check without tools and training. What's on the Colorado Bear standard fall tune-up:

• Flame sensor cleaning and test. The #1 mid-winter no-heat call is a fouled flame sensor. A tech pulls it, cleans it with fine steel wool, and re-tests. 10-minute task; prevents 80 % of "furnace won't stay lit" service calls.
• Combustion analysis. Measured O2, CO, stack temperature, and combustion efficiency with a calibrated analyzer, verified against the manufacturer's elevation-adjusted spec. Confirms the burner is safe and tuned.
• Heat exchanger inspection. Visual + camera inspection where accessible. Any hairline crack means an immediate replacement decision — a compromised heat exchanger can pass CO into the indoor airstream.
• Pressure switch and gas valve verification. Confirms the safety chain fires correctly on every start.
• Blower amperage and static pressure readings. Establishes a baseline for detecting winter-season wear.
• Thermostat calibration. Confirms the thermostat is reading actual room temperature within 1 – 2 °F.
• Refrigerant status on heat pumps. For dual-fuel and heat-pump-only homes: verify charge before winter heating demand.

Every one of these is a "tell before the failure" step. A properly run tune-up catches ~85 % of the failures that would otherwise become December or January emergency calls. Colorado Bear's fall tune-up runs $150 – $250 for a standalone visit; included in every maintenance-plan tier. See /plans for what's covered.

A tune-up in October is preventive medicine. A no-heat call in January is emergency care. The prices reflect that.

What to schedule and when

• September 1 – 15: Homeowner walkthrough. CO detectors, filter, humidifier prep, thermostat schedule.
• September 15 – October 15: Book the professional tune-up. Sweet spot before the first hard freeze and before every neighbor calls at once.
• October 15 – 31: Final walkthrough — outdoor unit clearance, snowfall prep, humidifier target set.
• December 1: Filter check. Replace if loaded.
• February 1: Second filter check. Note any changes in system behavior; call if anything feels off.

Cold snap emergency prep

The Front Range gets 1 – 3 sub-zero cold snaps per winter, usually 24 – 72 hours long. Two things worth doing before one arrives:

1. Know where the gas shut-off is. For any home with gas furnace, gas water heater, or gas cooking. If a leak develops during a cold snap, you'll want to be able to shut off gas at the meter without a flashlight-fumbling emergency.
2. Have Colorado Bear's after-hours number saved. Program (720) 790-3765 into your phone with a note. Emergency service during a Front Range cold snap gets busy fast; being a saved-contact customer moves you up the queue.

Twenty minutes of prep in September plus one professional tune-up in October is the whole recipe. Book the tune-up now at /contact if you're not already on a maintenance plan, or step up to a plan at /plans if this winter is going to be your first in the house. Then enjoy the season — the equipment is ready for it.