Furnace Replacement — Firestone
Furnace Replacement in Firestone, CO
Firestone is the most single-era town in the Carbon Valley: 45.7% of its homes were built in a single decade, the 2000s — and their original furnaces are now 17 to 26 years old. Oak Meadows, St. Vrain Ranch, Neighbors Point and the rest of the 2000s subdivisions are hitting first-replacement season together. This guide covers what furnace replacement actually costs in Firestone in 2026, what a first replacement involves, and when a repair still makes sense.
Guide by Zach Barbre · Denver HVAC expert
Updated October 2026 · Written from first-hand field experience in the north Denver metro · Prices verified against 2026 Denver-metro quotes
Get a straight answer on your furnace
Talk to a licensed local installer in Firestone. Free second opinions on replacement quotes — no pressure, no obligation.
Typical response time: under 15 minutes, 7am–7pm daily.
Is it the furnace, or something simpler?
Before you price a replacement, rule out the cheap fixes. In our experience these cause most "furnace trouble" calls in Firestone:
- Dead thermostat batteries or a tripped breaker — check these first, seriously.
- Clogged filter choking airflow — a two-story Firestone home asks one furnace to heat both floors; a starved filter shows up fast as short cycles and uneven rooms.
- Failed ignitor or flame sensor — a $400–$645 repair, not a $10,000 replacement.
Call now, don't wait: smell of gas, a carbon monoxide alarm going off, or water pooling under the furnace. Those are same-day problems.
Repair or replace? The honest fork
Repair it
Furnace is under 12 years old, the repair is under ~$800, and your heating bills haven't crept up. A good tech gets you 3–5 more years.
Replace it
15+ years old, second major repair in two years, cracked heat exchanger, or rooms that never get warm. At that point you're paying for heat you don't get.
Rule of thumb we stand behind: if the repair costs more than about a third of a new system and the equipment is past 12 years, replacement usually wins on math alone.
What furnace replacement costs in Firestone (2026)
The numbers: Firestone has about 20,000 residents — up from 16,381 in the 2020 Census — and the median home was built in 2009. Nearly 9 in 10 homes went up in 2000 or later: 45.7% in the 2000s, 31.5% in the 2010s, and 12.2% since 2020, with a small older core in Old Town. Most are two-story single-family homes with full basements. What that mix means for price: the house rarely complicates the job — ducts and venting are modern — so the variable is the equipment and the timing, because an entire town's worth of same-age furnaces fails on roughly the same schedule.
What moves you up or down inside that range:
- Efficiency rating — 80% AFUE vs 96%+ AFUE is the biggest price jump; 2000s homes vent modernly, so the high-efficiency route is usually straightforward here.
- Sizing — Builders sized original furnaces by square-foot rules of thumb, often a size large. A Manual J on the first replacement frequently lands smaller and heats more evenly.
- First-replacement details — Condensate routing, venting updates, and return-air checks the original builder-grade install never got; small line items that separate a careful quote from a box swap.
- Permits — Permit and inspection are included in reputable quotes.
In Firestone, the same furnace went into thousands of houses within a few years of each other, so failures arrive by subdivision, not by household. If your 2006 furnace is done, your neighbors' 2006 furnaces are done too — worth knowing in January, when every installer in the Carbon Valley is booked out. The homeowners who come out best plan the replacement in the shoulder seasons, or act at the first major repair bill on an original unit, instead of during a no-heat emergency in a cold snap. It's the same story one town south in Frederick, where the median home is a 2008 build. Ask any quote to state the size it calculated — not copied — in writing.
What happens when you call
- We answer and listen. You tell us the symptoms, the equipment's age, and your address. We confirm a licensed installer serves Firestone.
- A licensed local tech arrives. They diagnose, give you repair and replacement options in writing, and answer questions on the spot.
- You contract directly with the installer. The estimate, the work, and the warranty are between you and the licensed company doing the work — not with this guide.
- The installer warranties the work. Equipment warranty from the manufacturer, labor warranty from the installer, both in writing.
How this site works: Mile High HVAC Guide is an independent publisher. We don't install HVAC equipment. When you request help, we connect you with a licensed local contractor and may receive a referral fee from them. It never changes what you pay.
Questions Firestone homeowners actually ask
How long does a furnace replacement take?
Most straightforward swaps are one day — crew arrives in the morning, you're heating by evening. If ductwork or venting needs changes, plan for two.
Our Firestone home was built in 2005 — is the furnace original?
Probably, if it has never been replaced. Nearly half of Firestone was built between 2000 and 2009, and builder-installed furnaces typically run 15–20 years, so original units are failing across the 2000s subdivisions in the same few winters. The original was a builder-grade unit chosen for the development, not sized for your specific house — a first replacement is the right moment to verify sizing with a Manual J calculation instead of copying the old nameplate.
Do I need a permit for this in Firestone?
Yes — a furnace replacement in Firestone requires a permit from the Town of Firestone, and the contractor you hire is responsible for pulling it and completing the inspections, which the town handles through SAFEbuilt, its private building inspection partner. A permitted furnace replacement also triggers Colorado's carbon monoxide rule (C.R.S. § 38-45-102): an operational CO alarm within 15 feet of the entrance to each bedroom. You can verify a permit was issued by calling the town's Planning & Development department at 303-833-3291.
What size furnace does my house need?
It depends on square footage, insulation, and windows — not on what was there before. A proper installer runs a Manual J load calculation. 'Same size as the old one' without measuring is a red flag.
Get a straight answer on your furnace
Talk to a licensed local installer in Firestone. Free second opinions on replacement quotes — no pressure, no obligation.
Typical response time: under 15 minutes, 7am–7pm daily.