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Sizing a furnace correctly for this house is not a generic calculation a contractor can phone in from a catalog. Homes in Multnomah County, OR run heat about nine months a year, from October through June. The burner, the heat exchanger, and the ignition system cycle hard through that stretch, and a unit that was undersized at installation reaches the limits of those components sooner than one matched to the actual load. A contractor quoting a replacement here establishes the heat loss of the building first, because getting that number wrong at installation is what drives an early failure.
Existing ductwork is where a furnace installation either moves cleanly or stalls. Half the homes in Multnomah County, Oregon were built in 1972 or earlier (2020-2024 ACS 5-year). That means a large share of the housing stock was ducted for equipment generations removed from what a contractor is putting in today, and the runs, trunk sizes, and return configurations reflect that older system. A contractor quoting a new furnace here measures and assesses what is already in the walls before anything else on the job can be priced accurately.
What Gets Installed With a New Furnace
The furnace itself sits in a utility room, basement, or garage and is the unit that generates heat for the house. Attached to it is the flue or vent pipe, which carries combustion exhaust out through a wall or roof. A new installation means setting and connecting this unit so it has gas supply, a return air path, and a way out for exhaust.
The air handler components built into the furnace work alongside the blower motor, which pushes conditioned air into the supply side of the duct system. A thermostat mounts on an interior wall and serves as the control point for the whole system. The filter housing, positioned where return air enters the furnace cabinet, holds the filter that protects the blower and heat exchanger from debris.
The drawing shows a typical layout, and a licensed contractor determines exactly what the installation requires in your home.
Get matched in Multnomah CountyMultnomah County by the numbers
49 severe weather events were recorded in Multnomah County, Oregon 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 Multnomah County, Oregon were built in 1972 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesMultnomah County, Oregon holds 371,179 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 53.4% of the occupied homes in Multnomah County, Oregon (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesFurnace Installation Rules & Standards for Multnomah County, Oregon6 sourced codes 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 Multnomah County, Oregon
Oregon’s contractor licence does not reach casual, minor or inconsequential work on one structure where the person’s contracts total less than $1,000 — and the exemption is unavailable to anyone who advertises or signs themselves as a contractor, at any price.
Oregon requires a current Construction Contractors Board licence, with the right endorsement, to undertake, offer to undertake or bid construction work.
Severe Weather Events in Multnomah County
Weather puts real load on heating equipment, and how hard a furnace works over its life is shaped by the conditions it runs in. What holds for Oregon broadly shifts at the county level, which is why installation decisions here are best made with local conditions in view.
49 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.