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Sizing a furnace for a San Juan County home is not a generic calculation. Homes in San Juan County, CO run heat in every month of the year. The burner, heat exchanger, and ignition system cycle through every month, which means a contractor has to establish the true load the house places on the system before settling on equipment. Install a unit that runs harder than it should to keep up, and those components accumulate wear on a schedule the installer set from the start.
Ductwork sized and routed for an older heating system does not automatically carry a new furnace well. A contractor has to check what the existing runs can actually move before the equipment selection means anything. Half the homes in San Juan County, Colorado were built in 1979 or earlier (2020-2024 ACS 5-year). That spread across the housing stock is why so many installations here involve duct evaluation before the new unit is even ordered, and why the electrical service gets looked at alongside it.
What Gets Installed With a New Furnace
The furnace itself sits inside the home, most often in a basement, utility closet, or mechanical room. It holds the heat exchanger, burners, and blower in a single cabinet. That cabinet is the core of what a contractor brings in and connects to the rest of the house.
The flue pipe runs from the furnace cabinet up and out of the home, carrying combustion gases away. The thermostat mounts on an interior wall and tells the system when to fire. A contractor also sets the filter housing at the air intake, which is where return air enters before it reaches the burners.
The drawing shows a typical layout, and a licensed contractor determines exactly which components apply to your home and how each one gets positioned.
Get matched in San Juan CountySan Juan County, by the numbers
95 severe weather events were recorded in San Juan County, Colorado between 2015 and 2024.
NOAA National Centers for Environmental Information, Storm Events Database, bulk CSV export, events 2015-01-01 through 2024-12-31.Half the homes in San Juan County, Colorado were built in 1979 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesSan Juan County, Colorado holds 738 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 52.9% of the occupied homes in San Juan County, Colorado (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesFurnace Installation Rules and Codes for San Juan County, Colorado4 sourced standards and regulations
What the Installation Actually Looks Like
Non-weatherized gas furnaces manufactured on or after November 19, 2015 must reach 80.0 percent AFUE.
Non-weatherized oil-fired furnaces manufactured on or after November 19, 2015 must reach 83.0 percent AFUE.
Mobile home gas furnaces manufactured on or after November 19, 2015 must reach 80.0 percent AFUE.
Non-weatherized gas furnaces manufactured on or after December 18, 2028 must reach 95.0 percent AFUE, up from the 80.0 percent minimum that applies to units manufactured before that date.
Severe Weather History in San Juan County
Heating equipment works against the outdoor conditions it lives in, and those conditions vary by place. How hard a furnace has to work over its lifetime is a local question, and the weather record here is part of the answer.
95 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.