How deep a southern Maine attic should be, why the attic and not the roof decides ice dams, which material fits your attic, and what Efficiency Maine pays toward it. A new attic here is now held to R-60.
An attic in Cumberland, York or Sagadahoc County works for the boiler, the furnace or the heat pump for most of the year. NOAA's 1991–2020 normals for the Portland Jetport count 6,795 heating degree days and 144 nights at or below freezing, and every one of those nights pulls warm air up through whatever gaps the ceiling has.
So the job runs in a fixed order: measure what is up there, seal the attic floor, set baffles at the eaves, then blow insulation to a depth we mark on a ruler at the hatch. This page covers the depth the Maine code and ENERGY STAR ask for, the ice dam question, Capes and flat-roofed three-family houses, the materials, and what Efficiency Maine pays. The energy code and rebate guide has every table in one place.
Since April 7, 2025 the Maine Uniform Building and Energy Code has used the 2021 International Energy Conservation Code, and for climate zone 6, where all three counties sit, its attic figure for new work is R-60. ENERGY STAR's retrofit table lands in the same place for a bare attic, R60, and asks R49 of an attic that already holds three or four inches.
Inches depend on the material. ENERGY STAR reads an existing attic by multiplying the measured depth: cellulose comes to roughly 3.7 per inch, fiberglass batts 3.2, rock wool 2.8 and loose fiberglass 2.5. Run backward (our arithmetic, not a bag label), R-60 works out to roughly 24 inches of loose fiberglass or 16 of cellulose, and R-49 to about 20 or 13.
Efficiency Maine puts it bluntly in its list of weatherization myths: ice dams are not a roofing problem. They form when an attic is warmed by mistake, through air leaks, thin insulation or both. Snow over the warm part of the roof turns to water, which trickles toward the unheated overhang and freezes, so each thaw adds to a growing lip of ice at the edge.
Its insulation page adds what the backed-up water does: it can work under the shingles and run down into ceilings and walls. Raking the roof helps but is hard to keep up with, and one missed storm undoes it; heat cable works but costs money every hour it runs. Sealing the attic's leaks and adding insulation, Efficiency Maine says, can keep ice dams from forming at all.
Portland's normal snowfall is 68.7 inches a season by the National Weather Service's count, so the roof is covered for long stretches every winter. Icicles along the eaves after a cold, clear night are worth photographing for the assessment, because they show where the heat is getting out.
Insulation slows heat moving through it; it does very little about air moving past it. Efficiency Maine compares insulation without air sealing to a loose-knit sweater worn with no windbreaker. So before any fiber goes down, the openings between the rooms and the attic get closed:
Two more items come from Efficiency Maine's Weatherization Requirements Checklist: bath, dryer and kitchen fans that dump into the attic get ducted outdoors, and baffles go over the exterior walls at the eaves so the insulation never blocks the vent path. None of that is visible once the attic is full, which is why we photograph it. Air sealing has its own page.
Not every attic here is a flat floor you can walk across. Fine Homebuilding describes the older Cape Cod house this way: second-floor bedrooms tucked under the roof slope, short knee walls about four feet high, and triangular spaces behind them that are hard to insulate, so many Capes leak heat at the eaves, which is how ice dams get started.
There are two ways to handle that space. One treats it as outside: the knee wall and the floor behind it get insulated, with blocking sealed under the knee wall's bottom plate and between the rafters above its top plate so air cannot slip through the joist bays. The other brings the space inside by insulating along the rafters, with baffles kept open from eave to ridge. Which one fits depends on rafter depth, access and what is already there.
Portland also has the triple-decker. Greater Portland Landmarks describes it as three stories with one apartment on each floor, usually a rear porch, and often a flat roof, with Munjoy Hill holding many of them. A flat roof leaves no walk-in attic, so the top-floor ceiling is reached another way, decided after looking. The Census counts 17 percent of Portland's homes in buildings of three or four units.
For an open attic floor, blown insulation is the usual answer, and Efficiency Maine's checklist names it first: an open attic insulated to R-49 or more with blown-in material. Cellulose reaches a given R-value in fewer inches, by ENERGY STAR's factors, and either one is blown over the sealed floor to an even depth, eaves included.
Foam has its places. Where an attic is a closed cavity, such as a sloped ceiling or the space behind a knee wall, the checklist accepts dense-pack fill, closed-cell foam to within an inch and a half of the cavity's full depth, or open-cell foam filling it. Over all the surfaces of an attic it asks for five inches or more of closed-cell foam. Foam put in under the program also needs code-approved fire protection over it, and you are told how long to stay out while it cures. The spray foam page covers that side.
Whatever the material, the target goes in the written proposal as an R-value, not as a number of bags.
Efficiency Maine treats the attic as one zone: every attic and cathedral ceiling in the house, with the floors, walls and slopes that face it. Its current table, for attic upgrades finished from October 1, 2026 on, reads:
| Attic zone | Low income | Moderate income | Any income |
|---|---|---|---|
| Insulated, 250 to 499 square feet | $2,000 | $1,500 | $1,000 |
| Insulated, 500 square feet and up | $4,000 | $3,000 | $2,000 |
| Every accessible attic air leak sealed | $300 | $225 | $150 |
The conditions matter as much as the amounts. The attic has to start at an effective R-21 or less, which a well-insulated attic will not; the work has to be done by one of Efficiency Maine's Residential Registered Vendors to its checklist; the space has to be heated all season; and the paperwork reaches Efficiency Maine inside six months of completion. Households claiming the low or moderate tier get verified in advance, through HEAP, SNAP, TANF or MaineCare participation or an adjusted gross income up to $70,000 single or $100,000 joint. A home's lifetime limit is $8,600.
The federal 25C credit is not part of a 2026 price: it stopped covering work once 2025 was over.
Maine has one energy code, but each town runs its own permit desk. Most publish nothing about an attic top-up either way. Wells lists insulation work among jobs that need a permit; New Gloucester treats insulation as maintenance with no permit fee, and Bridgton exempts it inside the existing footprint. Each town page has the code office's number, and we settle the question with that office before the job is booked.
Two finds stop an attic job on the spot. Loose, pebble-like flakes that are gray-brown or silver-gold are vermiculite: EPA says to assume it holds asbestos and leave it undisturbed, and Maine's DEP wants professionals once more than three square feet of asbestos material will be disturbed. Live knob-and-tube wiring is the other: the electrical code forbids burying it in loose or foamed insulation, and Efficiency Maine will not pay on an attic where it is live in the insulated space. Insulation removal explains what happens next.
The state says its code covers renovations as well as new building, and the code's attic figure in climate zone 6 is R-60. Whether your town's code office checks an attic top-up is a question for that office. Efficiency Maine's own floor for a rebate is an open attic blown to R-49 or more.
Measure the depth in a few places, eaves included, and use ENERGY STAR's multipliers: each inch of cellulose is worth about R-3.7, an inch of batt about R-3.2 and an inch of loose fiberglass about R-2.5. If the joists show, you are almost certainly short of R-49.
Insulation alone helps less than people expect. Efficiency Maine's view is that ice dams come from heat reaching the attic through leaks and thin insulation, so the attic floor is sealed first and then insulated. That combination is what it says can stop them forming.
Only if what is there adds up to an effective R-21 or less, by Efficiency Maine's checklist. Many older attics with a few inches of matted batts qualify; one that already has a foot of fiber usually does not. We measure it so you know before anyone quotes.
It should not. Baffles go in at each eave bay over the exterior walls so the air path from the soffit stays open, and Efficiency Maine's checklist asks for them on every rebated attic.
It depends on the town. Wells lists insulation as permit work, New Gloucester and Bridgton say it needs none, and most towns publish no rule either way. Your town's page gives its code office's number.
Attic insulation across greater Portland and southern Maine, from the Casco Bay islands to the York County coast and the Sebago Lake towns. Each city has its own page with the permit rule and code edition that apply there:
Sources: Maine energy code since April 7, 2025 (2021 IECC) · Maine's energy chapter and its amendments · Zone 6 ceiling R-60 in the 2021 IECC table · ENERGY STAR R60 / R49 for zone 6 · ENERGY STAR depth multipliers and the joist check · Portland Jetport normals: heating degree days, freezing nights · Portland normal season snowfall · Ice dams, raking, heat cable, sweater comparison · Ice dams are not a roofing problem · Chimney sealing materials · Attic checklist: R-21 maximum, R-49 blown, baffles, dam, fans, foam · Attic zone and air sealing rebates, eligibility, lifetime limit · Rebate table applies to upgrades completed on or after 10/1/2026 · Capes, knee walls and blocking · Portland triple-deckers · Portland homes by units in structure (B25024) · Vermiculite · Maine DEP asbestos rule. Codes, programs and prices change; confirm the current rule with your city before you rely on it.
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