The largest block of Windham County’s housing is also its oldest. Of 49,918 units, 26.0% were built before 1940, more than in the 1960s and 70s (23.9%) or the 1980s and 90s (23.0%); 13.3% dates from the 1940s and 50s and 13.7% from since 2000. The newest town median is Sterling’s, 1986; the oldest, 1958, belongs to Putnam and the town of Windham.
Most of the county heats with oil: fuel oil or kerosene in 57.6% of occupied homes, electricity in 15.4%, utility gas in only 10.2%, bottled gas in 7.6% and wood in 7.2%, and nine of the fifteen towns have no gas company. Detached houses are 67.5% of units, two-unit buildings 7.3% and three- and four-unit buildings 8.3%, and 69.7% of occupied homes are owner-occupied. The return on sealing and insulating comes as oil deliveries skipped and wood not burned.
Windham County is Connecticut’s northeastern corner, the least populous of its eight counties and the heart of the Quiet Corner. Interstate 395 runs north through the mill towns of Plainfield, Killingly, Putnam and Thompson; the town of Windham, with the former city of Willimantic, meets Tolland County on the west; and Route 169, a National Scenic Byway, crosses the rural towns from Canterbury to Woodstock, annexed from Massachusetts in 1749. Fourteen towns belong to the Northeastern Connecticut Planning Region, and Windham to the Southeastern. The seven town pages carry the detail.
The Windham County towns we work in
Ashford, Canterbury, Chaplin, Eastford, Hampton, Pomfret, Scotland and Sterling have no page of their own; their houses are counted in every county figure.
- Brooklyn — home of the Brooklyn Fair and General Israel Putnam’s resting place; 9.7% wood heat and 9.2% propane.
- Killingly — the state’s largest maker of cotton goods in the 1830s; 12.4% built in the 1960s, the most of the seven.
- Plainfield — the county’s southernmost town, with Moosup and Wauregan: 27.1% built in the 1960s and 70s, the most of the seven.
- Putnam — flooded by the Quinebaug in August 1955; 32.5% of units in two- to four-family buildings, the most of the seven.
- Thompson — North Grosvenordale’s mill district to Quaddick Reservoir; 12.9% built in the 1950s, the most of the seven.
- Windham — the town that holds Willimantic, a city from 1893 to 1983; 78.1% built before 1980, the most of the seven.
- Woodstock — Roseland Cottage’s old summer town: 85.9% detached and 10.2% on propane, both the most of the seven.
Four of these names repeat elsewhere. Windham is a town, not the county; Putnam, named for General Israel Putnam, is not Putnam County, New York; and Brooklyn and Woodstock are not the New York borough or Woodstock, New York.
The houses across Windham County
The mill villages hold the oldest, densest housing, from Willimantic’s factories and Killingly’s cotton mills to Plainfield’s mills on the Moosup and Quinebaug rivers and the mill districts of Putnam, North Grosvenordale and Brooklyn’s Quebec Square. Putnam is 40.7% pre-1940, with 18.0% of units in two-unit and 14.5% in three- and four-unit buildings; the town of Windham is 34.9% pre-1940, with 15.2% in three- and four-unit buildings; Plainfield is 29.6% and Killingly 24.6%. Most wood-frame multifamilies of that age are balloon-framed, so a wall bay can run from the cellar sill to the attic without a single block, and the stairwell works as a chimney for the whole building. Live knob-and-tube wiring means an electrician goes first. Only 45.2% of Windham’s homes are owner-occupied, so there the landlord usually decides.
The other old houses stand on the greens and hills: the Brooklyn Green and Bush Hill historic districts, Thompson Hill, Windham Center and Woodstock Hill. They are fewer, 10.8% of Woodstock’s stock and 14.8% of Brooklyn’s predating 1940, but take the most care. A post-and-beam house has braces that break its walls into odd bays, clapboards that last only if the wall can dry, and a big chimney that leaves a gap at every floor. We leave those walls alone and work the attic floor, the chimney gaps, the sill on its stone foundation and the later ell over its crawl space.
The 1940s and 50s built 13.3% of the county but 17.1% of the town of Windham, 16.3% of Killingly and 15.0% of Thompson, 12.9% there in the 1950s alone: capes and small ranches. Behind a cape’s knee walls the floor joists run out to the eave, an open channel from the cold attic into the ceiling below that more batts upstairs never close. A ranch leaks through dozens of small holes in one long ceiling, under insulation packed down for seventy years. Mobile homes, 2.0% of the county’s units and 4.4% of Thompson’s, are a separate conversation.
The 1960s and 70s produced 23.9% of the housing, and the 1970s, at 14.0%, are the biggest single decade: Plainfield is 27.1% from those twenty years, Thompson 27.0%, Windham 26.1% and Killingly 25.1%. Their builders put batts in, so the losses sit at the joints: a raised ranch’s band joist exposed above the soil, a bedroom floor over a cold garage, a garrison’s overhang, and every attic top plate. Electricity heats 15.4% of the county’s homes, 26.7% in Putnam and 21.7% in Windham, and under baseboard heat each lost unit is billed by the kilowatt-hour.
Woodstock and Brooklyn lean newer. Woodstock’s median home dates from 1984, with 38.9% of its stock from the 1980s and 90s and 22.9% since 2000; Brooklyn has 24.6% and 22.0%. Their walls are full, so the work moves to the edges: a vaulted great room whose batts touch the roof sheathing, a bonus room floor above a cold garage, the attic side of every recessed light and bath fan, and a rim joist behind a finished basement wall. Propane heats 10.2% of Woodstock homes, and attic ductwork loses heat before the air reaches a room.
What a house burns matters as much as its framing. Oil heats 68.5% of Thompson’s homes, 64.0% of Plainfield’s and 59.9% of Woodstock’s; wood heats 12.3% in Thompson and 9.7% in Brooklyn; and with no gas company, Thompson has 0.0% gas heat. A tighter house changes how a chimney draws, so on oil or wood we test the draft before and after, and nothing goes inside a wood stove’s clearances. In Putnam, where the August 1955 Quinebaug flood destroyed homes and factories, a cellar that takes water gets its sill and rim sealed, not foam on its walls.
We seal before we insulate
A foot of new insulation on an attic floor does nothing about air rising past it from an open wall bay, a chimney chase or a loose hatch. Insulation slows conducted heat; only sealing stops the air that carries heat out.
In a mill-village two- or three-family the sealing runs from the bottom up: the cellar sill and rim, then each balloon-frame bay blocked at the cellar and again at the attic, the stairwell hatch weatherstripped, and plumbing and chimney chases capped with metal and fire-rated sealant, all before the attic and walls get insulation. In a post-and-beam farmhouse it starts at the sill and ends at the chimney gaps in the attic floor.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Windham County
Most of our projects run between $3,500 and $12,500. Three things move the number here: how many units share the envelope, since a two-family or three-unit mill house is scoped as one building with wall bays and a stairwell running through every unit; access, since a farmhouse’s walls stay closed while a raised ranch’s rim and garage ceiling are quick to reach; and how much closed-cell foam the rims, vaulted ceilings and bonus-room floors need.
Open cell foam runs R-3.9 to R-4.2 per inch. Closed cell runs R-6.9 to R-7.1 per inch and also acts as a vapor retarder, which is why it costs more and why it is right in some assemblies and unnecessary in others. All products are manufactured in the United States and meet applicable building code and safety standards. ENERGY STAR says sealing air leaks and adding insulation can save up to 10% on annual energy bills.
Insulation rebates in Windham County
Eversource delivers electricity in all fifteen towns and is the gas company in Brooklyn, Killingly, Plainfield, Pomfret, Putnam and Windham. Ashford, Canterbury, Chaplin, Eastford, Hampton, Scotland, Sterling, Thompson and Woodstock have no local gas company. A listed gas company does not mean a main on every road: utility gas heats 7.2% of Brooklyn homes.
The programs belong to Energize Connecticut, paid for by a charge on customer energy bills. Home Energy Solutions is open to customers of Eversource, United Illuminating, Connecticut Natural Gas and Southern Connecticut Gas, whatever fuel heats the house, in homes of one to four units that have not had these services in the last six years, and renters first need their landlord’s approval. The visit costs a $40 copay on the standard tier, effective 1 April 2026. It begins with health and safety tests and a blower-door test, adds a duct test where there is forced hot air or central air conditioning, and includes up to seven hours of air sealing at no cost, then $10 an hour. Two- to four-unit properties require two visits, a house built before 1985 may be recommended for two, and there may be a waiting list.
Once insulation is recommended at a visit, the 2026 Energize CT insulation rebate covers attic floors, floored-over attics, walls, basement and garage ceilings and rim joists at up to $2.00 per square foot or 75 percent of the total cost, whichever is less, up to a maximum of $10,000; spray foam is an accepted material. A wall qualifies at R-4 or less and must finish at R-13 or more, so an empty mill-house wall usually does; an attic floor at R-19 or less must reach R-49, or R-38 where the structure cannot take more. Foam on the underside of a roof deck is not on that list, so ask the program before counting on a rebate for it. The project must be approved before installation and installed by an approved contractor from the Energize CT Insulation Installers Network.
For two people, Energize CT’s 2026–2027 limits put $63,703 or less in Income Eligible, with up to 100 percent coverage of insulation costs, and $63,704 to $84,939 in Enhanced Incentives, a range that shifts by zip code, with a no-cost visit and up to $2.50 per square foot. Every address in Chaplin, Killingly, Plainfield, Putnam, Sterling and Windham is in a state-designated environmental justice community, which can raise the Energize CT insulation incentive to $2.50 per square foot, up to $15,000. Parts of Ashford, Brooklyn and Thompson are designated environmental justice communities; the state’s map shows whether a specific address qualifies.
The Energize CT insulation rebate is paid only on work by the program’s network installers, so ask any installer who quotes, including us, whether they are in that network, and compare prices after any rebate before you decide. Households at or below 60% of state median income can also apply to the state’s Weatherization Assistance Program.
Financing comes through the Connecticut Green Bank’s Smart-E Loan: no money down, up to $50,000, and 6.99% APR for 5, 7 or 10 years, 7.49% for 12 or 7.99% for 15 where a lender offers it, on owner-occupied homes of one to four units. The Smart-E Loan is arranged through the Green Bank’s participating contractors; ask whether your contractor participates. The Section 25C credit is not allowed for anything placed in service after 31 December 2025, so no federal tax credit applies to insulation installed in 2026, and the federal Home Energy Rebates are not available in Connecticut. Our Connecticut insulation rebate guide has the full rules.
Code and climate in Windham County
63.3% of Windham County’s housing was built before 1980; among the seven towns with pages the share runs from 78.1% in Windham down to 38.2% in Woodstock. The county sits in climate zone 5A, as the whole state does, with a 7°F winter design temperature.
For a new house or addition whose application was filed on or after 1 October 2022, the rules are the 2022 Connecticut State Building Code, built on the 2021 IECC with state amendments. Ceilings need R-60, though R-49 counts where it reaches full, uncompressed depth over the wall top plate at the eaves. Wood-frame walls need R-30 cavity, R-20 cavity with R-5 continuous, R-13 with R-10 continuous, or R-20 continuous; floors R-30; basement and crawl space walls R-15 continuous, R-19 cavity or R-13 cavity plus R-5 continuous; windows U-0.30. A new home’s blower-door limit is 3.0 air changes per hour at 50 pascals on the prescriptive path, 5.0 at worst; an addition’s new envelope is exempt from that test. Connecticut’s next code, based on the 2024 IECC, has been adopted in draft, but its effective date has been delayed.
Common questions about insulation in Windham County
Do you install insulation in Windham County, CT?
Yes. We work in all fifteen towns, from Brooklyn, Killingly, Plainfield, Putnam, Thompson, Windham and Woodstock to Ashford, Canterbury, Chaplin, Eastford, Hampton, Pomfret, Scotland and Sterling. The houses run from mill-village two- and three-families in Willimantic, Danielson, Moosup and Putnam to post-and-beam houses on the old greens, 1950s capes, 1970s raised ranches and the newer houses of Woodstock and Brooklyn. A building of five or more apartments starts with its owner.
How much does insulation cost in Windham County?
Most projects run $3,500 to $12,500. A mill two- or three-family is quoted as one building, by its wall bays, stairwell and top-floor roof. A farmhouse depends on its attic floor, chimney, sill and any ell over a crawl space; a raised ranch on its rim joist and garage ceiling; a newer colonial on its bonus room, vaulted ceilings and attic ducts. Closed-cell foam costs more per inch than open cell or blown insulation, so it goes where its air seal or vapor control earns the cost.
Are there insulation rebates in Windham County?
Yes, through Energize Connecticut, open to Eversource customers in every town. The standard-tier Home Energy Solutions visit carries a $40 copay, and the income-qualified tiers pay nothing. The insulation rebate then pays up to $2.00 per square foot or 75 percent of cost, whichever is less, to $10,000, for work recommended at the visit, approved in advance and done by a contractor in the Energize CT Insulation Installers Network. Addresses in Chaplin, Killingly, Plainfield, Putnam, Sterling and Windham, and some in Ashford, Brooklyn and Thompson, can reach $2.50. No federal credit applies in 2026.
Which utility do I have in Windham County?
Electricity comes from Eversource everywhere in the county. Eversource is also the gas company in Brooklyn, Killingly, Plainfield, Pomfret, Putnam and Windham, though a main may not reach your road; Ashford, Canterbury, Chaplin, Eastford, Hampton, Scotland, Sterling, Thompson and Woodstock have no local gas company. Either an Eversource electric account or an Eversource gas account can open Home Energy Solutions. The names on your bills settle which accounts you have.
Free estimate in Windham County
The free estimate is a walk-through we do ourselves; it is not a Home Energy Solutions visit and does not make a house eligible for a rebate. In a mill-village multifamily we check the cellar sill, wall bays, stairwell and top-floor roof, and ask who owns the building; in a farmhouse, the attic floor, chimney, sill and ell; in a raised ranch, the rim and garage ceiling; and wherever oil, propane or wood burns, the boiler, furnace or stove. You get the scope and price in writing, free and without obligation.
The number is 914-825-6824, answered 8am–8pm seven days a week, and the contact form works too. Our 100-plus in-house crew is based in New Rochelle, NY, and never subcontracts.
Learn more
- Insulating the walls of an existing house
- Insulating an older home
- Air sealing
- Basement and rim joist insulation
- Attic insulation
- Insulation contractors across Tolland County
- Insulation contractors across New London County