Insulation in Nantucket, Massachusetts

Nantucket is in Eversource territory (served by the island electric system under Eversource), so homeowners qualify for Mass Save. Insulation and air sealing are the program's flagship weatherization measures, and as of recent rebate cycles Mass Save covers roughly 75 to 100 percent of approved costs (100 percent for income-eligible households). A no-cost Mass Save Home Energy Assessment is the first step.

The 0 percent Mass Save HEAT Loan, up to $25,000, finances the homeowner share. Mass Save is geared to a primary residence, so seasonal-home owners should confirm occupancy rules. Older island houses commonly flag knob-and-tube or vermiculite in pre-1981 attics.

Insulation on Nantucket usually needs no standalone building permit, but the contractor should carry a Massachusetts Home Improvement Contractor (HIC) registration, with a Construction Supervisor License (CSL) for related structural work. Mass Save jobs must run through a participating, approved contractor. Spray foam has to meet the state fire and ignition-barrier code. Nantucket's Historic District Commission governs the entire island, so any exterior change is reviewed closely — interior insulation generally is not, but confirm before touching the exterior.

Nantucket pricing runs well above mainland Massachusetts because materials and labor often travel by ferry and the island's contractor market is tight and seasonal. As of recent cycles mainland anchors are attic insulation $1,500 to $4,000, dense-pack wall insulation $2,000 to $6,000, and air sealing $300 to $1,500, but island quotes routinely come in higher. Because Nantucket is a Mass Save town, the 75 to 100 percent incentive can still bring net out-of-pocket close to zero for an eligible primary residence once the assessment approves the scope.

Nantucket is its own county, an island town with about 14,065 year-round residents but roughly 12,287 housing units, many of them seasonal — the year-round and seasonal split defines the local market. The median construction age is near 42 years, though that figure masks a core of nationally significant 18th- and 19th-century houses in town alongside late-20th-century homes elsewhere on the island.

For insulation, that means two very different jobs: weatherizing newer year-round homes with attic and air-sealing work, and carefully retrofitting historic houses where exterior changes are tightly controlled and wall cavities may be empty. Salt air and exposed wind raise the value of a tight envelope across the island.