Insulation in Bath, Maine

Insulation and air sealing in Bath

Bath runs to about 9.1 square miles and roughly 8,815 people. It sits about 28 miles northeast of downtown Portland. Around 4,796 housing units sit inside those boundaries. The community dates back to 1781. We cover ZIP code 04530.

No completed job in Bath is logged in our records yet, and this page will say so until one is.

The housing stock in Bath

The typical home in Bath dates to around the 1930s or earlier. Houses built before the war generally went up with nothing in the walls at all and whatever went into the attic afterwards. Anything up there was added later, usually in a hurry.

The South End is the older residential area with early 1800s houses, the North End holds the densest mix of 19th-century homes built by prospering shipbuilders, many Greek Revival and Italianate, and Washington Park was built as housing for shipyard workers during World War I.

We work across Bath rather than one corner of it — Downtown, North End, South End and Washington Park included. Construction and vintage change between them, sometimes by thirty years and a whole different framing method, which decides whether a wall can be dense-packed at all.

Bath is a small city on the west bank of the Kennebec River, about 12 miles up from the open ocean, known as the City of Ships; it became a town in 1781 and a city in 1847. Shipbuilding began here in 1743, Bath Iron Works has built hundreds of ships, mostly for the Navy, and many of the older neighborhoods were built during the shipbuilding boom. The older core is a National Register district, and a city historic overlay zone reviews some exterior changes there.

Bath homes in the Census numbers

The Census Bureau estimates 4,796 homes in Bath. 2,756 of them (57%) went up before 1940 — the highest share of pre-1940 housing among the 64 places on this site. More of today's homes date from before 1940 than from any single decade since, and 79% predate 1980. For Sagadahoc County as a whole the pre-1940 share is 27%, so Bath sits above it.

Of 4,335 occupied homes, 6% heat with utility gas and 20% with electricity; another 20% burn propane or other tank gas. Electric heat here is more common than across the county (11%), and ranks 2nd of 64 on this site. The heating fuel does not change the Efficiency Maine rebate, but it does change what each inch of insulation is worth, which is why the boiler, furnace or heat pump is the first thing an assessment looks at.

64% of occupied homes are owner-occupied and 60% of all homes are single-family detached houses. Read together, those numbers point toward wall insulation for walls built empty and a vermiculite check before anything is disturbed.

4,796 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 4,335 occupied.

Sealing comes first in Bath

3,006 of Bath's 4,796 homes (63%) went up before 1950. In houses that old the air leaves before any insulation can slow it: balloon-framed bays open from the sill to the attic, open chases behind knee walls, plaster-and-lath ceilings leaking at every fixture. Those get blocked and sealed first. Two checks come before any quote on a house this old: loose gray-brown flakes in the attic, and cloth-covered wiring on ceramic knobs.

What the energy code requires in Bath

Bath enforces the Maine Uniform Building and Energy Code (2021 IECC with Maine amendments). Bath is bound by the state code, and its September 2026 Permit Requirements and Conditions sheet cites the 2021 residential and building codes; two older city handouts still list the 2015 editions.

Under that edition the required attic value for new work here is R-60, and walls R-30, or R-20 + R-10 continuous, or R-13 + R-15 continuous, or R-20 continuous. For comparison, the Department of Energy recommends R60 for an uninsulated attic in climate zone 6A, where Bath sits, and R49 where there are already a few inches up there.

Table R402.1.3 of the 2021 IECC for climate zone 6, with the wall row as Maine rewrote it (08-003 C.M.R.

Do you need a permit to insulate here?

Nothing Bath publishes settles this. Its permit lists name the work types it cares about, and insulation is not among them in either direction. Bath's Land Use Code (adopted September 2, 2026) requires a building permit before a building is constructed, structurally altered, enlarged, moved or demolished; insulation is not named, and a permit taken out after work has begun costs five times the fee. So we ask the department directly before the first day on site, and whatever comes back, pulling it is our job rather than yours.

Permits and inspections in Bath

The published number is 207-443-8334. The department page is here.

Permitting is on us, not on you.

Rebates a Bath homeowner can actually use

Heating fuel in Bath, by the Census Bureau's count: fuel oil or kerosene in 47% of occupied homes, electricity in 20%, propane or tank gas in 20%, and 6% utility gas (Census ACS 2020–2024). For Bath homeowners the rebate is Efficiency Maine's: $2,000 for each attic, wall or basement zone of 500 square feet or more at any income ($3,000 moderate, $4,000 low income), with $150 to $300 for attic air sealing on top. The work has to be done by an Efficiency Maine Residential Registered Vendor, and the attic has to start at R-21 or below and finish at R-49 or more. Income-qualified households in Sagadahoc County can apply to Kennebec Valley Community Action Program (207-859-1500) for free weatherization through MaineHousing instead. See the rebate guide for the tiers and the checklist, and the Sagadahoc County page for the county.

Nearby

Bath borders Woolwich, Arrowsic, West Bath, Phippsburg, Brunswick and Kennebec River. These are the ones we also cover, each with its own energy code and permit rule:

Elsewhere in Sagadahoc County we also cover:

How Bath compares with its neighbors

Maine sets the residential energy code statewide, so the attic figure is R-60 wherever it is published here; what changes is the permit desk, and 1 of the 7 publishes a permit rule for insulation.

All 10 Sagadahoc County jurisdictions side by side →

Common questions about insulation in Bath

Code and permit facts checked October 24, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: cityofbathmaine.gov (2, 3, 4, 5, 6, 7, 8, 9, 10, 11) · maine.gov (2, 3, 4) · en.wikipedia.org (2, 3, 4, 5, 6, 7, 8, 9) · npgallery.nps.gov · pressherald.com · zip-codes.com · efficiencymaine.com (2, 3, 4) · energystar.gov · data.census.gov. These change; confirm with the building department at 207-443-8334 or Efficiency Maine at 866-376-2463 first.