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A contractor sizing a furnace in Randolph County works from the house, not from the weather calendar. 63 severe weather events were recorded in Randolph County, Illinois between 2015 and 2024. At that rate, severe weather is something a system encounters now and then, not something it fights through every season. What that means for a new install is that the case for careful sizing and proper duct work rests on the building itself, its age, insulation, and layout, not on weathering a punishing climate. A furnace put in loose or undersized here will underperform for reasons the next contractor will find in the equipment, not outside it.
Ductwork sized and routed for an older system carries real constraints on what a new furnace can do once it is in. Half the homes in Randolph County, Illinois were built in 1972 or earlier (2020-2024 ACS 5-year). A contractor installing a furnace here has to assess whether the existing trunk lines and branch runs will move air the way the new unit needs, and whether the electrical service at the panel will carry the load. If the ductwork cannot, the scope of the job changes before the furnace itself is even priced.
What Gets Installed With a New Furnace
The furnace itself sits in the basement, utility room, or crawlspace and is the unit that generates heat. Attached directly to it is the air handler, which pulls household air across the heat exchanger and pushes warmed air out through the supply side of the duct system. Together these two pieces are the core of what a contractor sets in place.
The flue pipe runs from the furnace up and out of the house, carrying combustion gases outside. Alongside it, the contractor installs the gas line connection, the condensate drain on high-efficiency units, and the thermostat wiring that ties the controls to the new equipment. Each of these sits at a specific point in the system and gets connected as part of the same job.
The drawing shows the general layout of a furnace system, and a licensed contractor determines exactly which components apply to your house and how they connect.
Get matched in Randolph CountyRandolph County, by the numbers
63 severe weather events were recorded in Randolph County, Illinois 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 Randolph County, Illinois were built in 1972 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesRandolph County, Illinois holds 13,422 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 76.6% of the occupied homes in Randolph County, Illinois (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesFurnace Installation Rules for Randolph County, Illinois5 sourced rules and standards
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.
Licensing Rules for HVAC Work in Randolph County, Illinois
Illinois leaves HVAC licensing to the municipality: state law lets the corporate authorities of each city or village examine, license and regulate heating, air conditioning and refrigeration contractors, and caps the licence fee they may charge at $50 — so who licenses you depends on the town you work in.
Severe Weather Events in Randolph County
Weather in this part of Illinois puts real demands on heating equipment, and those demands shape what a furnace installation here needs to handle. That makes local weather history a practical reference, not background noise.
63 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.