Furnace Installation & Replacement in Thornton

Areas built from 1970 to 1999, including Cherrywood Park and Quail Valley, have mostly two-story and split-level homes on second or third furnaces. Furnaces from 2000s replacements are now about 20 years old. Many of these homes moved to condensing furnaces during an earlier replacement, so the PVC vent may be reusable after checks. Where the house still has an 80% furnace on a B-vent, the same two-path choice applies as in the older ranches. Split-levels in particular benefit from a two-stage or variable-speed furnace, because their lower and upper levels have very different heat needs that a single-stage furnace tends to overshoot.

Holly Crossing, Briar Ridge, Holly Point and Grange Creek include many homes built since 2000. Original condensing furnaces from the early 2000s are entering the replacement window. Production-built homes were often fitted with one furnace size per floor plan, so a Manual J for your actual house can point to a smaller furnace or a two-stage model. We also replace the condensate trap and drain line and check that sidewall vent terminations clear windows, decks and snow lines.

At about 5,210 feet, furnaces lose roughly 21% of their sea-level rating, so an 80,000 Btu/h input furnace delivers about 63,000 here after high-altitude setup. Since January 1, 2026, a new gas furnace must meet Colorado's 14 ng/J NOx limit or the current ENERGY STAR version (97% AFUE in the North since July 31, 2026). See our NOx guide.

About 4.6% of Thornton's homes are mobile homes. Those need furnaces listed for manufactured housing, not standard residential units, and they must also meet the NOx rule; the 2026 propane and mobile-home exemption covers water heaters, not furnaces.

Furnace replacement is on the city's list of mechanical work that needs a permit. We file it with the Building Division, then book and attend the inspection. Gas comes from Xcel Energy; a rebate tracker reports Xcel ended gas furnace rebates on January 1, 2026. Electricity comes from Xcel or United Power depending on address, which decides which heat pump rebates you can use.

Colorado's $1,000 air-source heat pump credit and Power Ahead Colorado's $1,500 cold-climate rebate apply regardless of utility. Our heat pump cost guide covers typical metro pricing if you want to compare.