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Sizing a furnace for a house in Oakland County starts with what the climate actually asks of the equipment, and severe weather here is frequent enough that a contractor has to factor it into every load calculation. 210 severe weather events were recorded in Oakland County, Michigan between 2015 and 2024. At that rate, a system that was sized to a national average or installed without attention to local demand will fall short during the stretches that matter most. A contractor quoting a furnace replacement here works out the real heating load for the structure before specifying equipment, because an undersized install runs hard, wears faster, and still leaves the house cold on the worst days.
Ductwork laid out for an older generation of heating equipment carries real constraints when a contractor fits a new furnace to it: the trunk lines, the branch runs, the return paths were all sized for something else. Half the homes in Oakland County, Michigan were built in 1975 or earlier (2020-2024 ACS 5-year). That gap between the building and the equipment running in it now is where furnace installation work gets decided. A contractor has to assess whether the existing duct system moves air the way a new unit needs before the equipment itself gets priced or ordered.
What Gets Installed With a New Furnace
The furnace itself sits in the basement, utility room, or crawl space and is the unit a homeowner would recognize on sight. Inside it, a heat exchanger warms the air that moves through the house, and a blower motor pushes that air out into the supply side of the duct system. The burner assembly and the ignition control sit within the same cabinet.
The flue pipe runs from the furnace up and out of the house, carrying combustion gases away from the living space. Alongside the furnace, a new thermostat goes on an interior wall and gives the homeowner direct control over when the system fires and what temperature it holds.
The drawing shows a representative layout, and a licensed contractor determines which components and configurations apply to your specific house.
Get matched in Oakland CountyOakland County, by the numbers
210 severe weather events were recorded in Oakland County, Michigan 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 Oakland County, Michigan were built in 1975 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOakland County, Michigan holds 561,348 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 72.7% of the occupied homes in Oakland County, Michigan (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesFurnace Installation Rules & Standards for Oakland County, Michigan6 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 and Legal Requirements in Oakland County, Michigan
Michigan issues the mechanical contractor’s licence by classification: HVAC equipment, ductwork, refrigeration, hydronic heating and cooling, and limited or unlimited heating and refrigeration service are each a separate classification a contractor has to hold.
Michigan requires a mechanical contractor’s licence: nobody may install, alter or service the regulated mechanical work unless they, or an employee, hold a licence from the department that has not been revoked or suspended.
Severe Weather Events in Oakland County
Oakland County winters put real load on heating equipment, and summer swings do the same to cooling. How hard a furnace or air handler works over its life is a local question, and local weather conditions are part of the answer.
210 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.