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Sizing a boiler for this house is the first thing a contractor has to get right, because the margin for error is narrow. Homes in Chittenden County, VT run heat about nine months a year, from September through May. The burner, the heat exchanger, and the ignition system cycle through that load every year, and the wear they accumulate is not evenly spread across all components. A unit that was undersized at installation, or one where the flue and combustion air were set up carelessly, strains on those parts earlier and harder than the equipment was rated for. Contractors quoting a replacement here factor that history into what they specify.
Existing ductwork in a house decides more about a boiler installation than the boiler itself does. Half the homes in Chittenden County, Vermont were built in 1981 or earlier (2020-2024 ACS 5-year). That places a large share of the county's housing stock in a position where the distribution system was laid out for equipment that is no longer in the house. A contractor quoting a new boiler has to trace what is actually there, where it runs, and whether it can carry what the new system requires, before the equipment selection means anything.
What a New Boiler System Puts in Your Home
The boiler itself sits in the basement or utility room and heats water that the system sends through the house. Alongside it, the expansion tank absorbs pressure changes as that water heats and cools, and the circulator pump pushes the hot water through the pipes to wherever heat is needed.
Baseboard radiators or radiant floor pipes receive that water in each room and give off the heat before sending the cooler water back. The thermostat mounts on a wall where the household controls the temperature, and the flue pipe runs from the boiler to an outside vent to carry combustion gases out of the building.
The drawing shows a typical layout, and a licensed contractor determines exactly which components and configurations apply to your home.
Find a contractor in Chittenden CountyChittenden County by the numbers
196 severe weather events were recorded in Chittenden County, Vermont 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 Chittenden County, Vermont were built in 1981 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesChittenden County, Vermont holds 74,888 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 63.9% of the occupied homes in Chittenden County, Vermont (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesBoiler Installation Rules for Chittenden County, Vermont2 codes & standards
Licensing Rules for Chittenden County, Vermont
Vermont splits the trade across two specialty licences and a contractor may hold one without the other: field A1 covers automatic gas or oil heating including geo-thermal and ground source heat pumps, and field C3 covers refrigeration or air conditioning including air-to-air heat pumps.
Vermont reaches HVAC work through its electricians’ licence rather than an HVAC licence, and the requirement stops at the front door of a house: anyone performing electrical work in Vermont must be licensed as an electrician unless the work is in a residential building containing two or fewer dwelling units.
Severe Weather Events in Chittenden County
Vermont winters put real load on boilers, and the weather that passes through a county shapes how hard that equipment has to work over its lifetime. A boiler sized and installed for local conditions holds up differently than one that was not.
196 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.