Tell us about the job
Takes about a minute. No obligation.
Sizing a furnace for this house is not a step a contractor can estimate from square footage alone. Homes in Sullivan County, NH run heat about nine months a year, from September through May. The burner and heat exchanger cycle through nearly every month on the calendar, and an undersized system runs longer each cycle to meet setpoint, grinding through the ignition system and stressing the heat exchanger at both ends of the season. A contractor quoting a replacement here runs a full load calculation before settling on equipment, because an install that looks adequate in a mild week will fall short once January arrives and keep falling short until it fails.
Ductwork laid down for equipment that has since been replaced once, or twice, carries its own history of patches, resizing, and re-routing. Half the homes in Sullivan County, New Hampshire were built in 1974 or earlier (2020-2024 ACS 5-year). That is the condition a contractor opens up to in much of this county, and it is what decides whether a furnace installation is straightforward or whether the duct system has to be reworked before the new unit can be connected. The electrical service runs a close second: panels sized for older loads do not always have the capacity a modern furnace and its auxiliaries draw.
What Gets Installed With a New Furnace
The furnace itself sits in the basement, utility room, or mechanical closet and is the piece doing the heating work. A gas valve, a heat exchanger, and a blower motor all live inside the cabinet. The contractor mounts and connects the cabinet as a unit.
The flue pipe runs from the furnace out through a wall or roof to exhaust combustion gases safely. The thermostat goes on an interior wall and gives the homeowner control over when the system runs. A new furnace also gets a fresh filter housing where the return air enters the cabinet before it passes through.
The drawing shows a typical layout, and a licensed contractor determines exactly what applies to your house.
Find a contractor in Sullivan CountySullivan County, NH, by the numbers
111 severe weather events were recorded in Sullivan County, New Hampshire 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 Sullivan County, New Hampshire were built in 1974 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesSullivan County, New Hampshire holds 21,958 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 75.4% of the occupied homes in Sullivan County, New Hampshire (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesCodes & Standards Governing Furnace Installation in Sullivan County, New Hampshire6 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 Sullivan County, New Hampshire
New Hampshire's mechanical licensing board issues nine credentials — hearth system, four fuel gas endorsements, domestic appliance technician, and master, journeyman and apprentice plumber — and a licensee may not work outside the specialty their licence names. None of the nine is an HVAC licence.
New Hampshire does not license HVAC as a trade, and says so where it matters: the plumbing licence expressly does not reach a person installing heating, cooling, air conditioning or domestic water heating systems, whether solar, oil, gas or electric. The gas piping on a gas-fired system is a separate matter and needs a fuel gas fitter licence.
Severe Weather Events in Sullivan County
Furnaces in Sullivan County work against whatever the local climate delivers, and how hard that is varies year to year. The record of severe weather events here shapes how contractors size and install equipment built to last under real local conditions.
111 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.