Insulation · Air Sealing · Maine Energy Code
Your Maine home leaks heat. The code, the physics, and the fix are all right here.
Home Insulation Maine is the independent knowledge base for insulating stick-built homes in Maine. We explain how the thermal envelope works, why air sealing comes first, what MUBEC requires, and when Maine law forces an insulation upgrade. When you're ready for the work, we connect you with our recommended installers — BRF Services and Maine Energy Services.
Why this matters in Maine
The longest heating season in New England, running through the leakiest housing stock
Maine homes work harder than almost any other homes in the country. Most of the state sits in IECC Climate Zone 6 — the second-coldest zone in the national classification — and Aroostook County sits in Zone 7. Heating seasons routinely exceed 7,500 heating degree days, and much of our housing stock predates any statewide energy code at all: Maine has some of the oldest homes in the nation, built when fuel was cheap and insulation was an afterthought.
The result is predictable. Oil, propane, kerosene, wood, and electricity pour into Maine houses every winter, and a large share of that heat leaves through under-insulated attics, empty wall cavities, uninsulated foundations, and — most of all — through air leaks driven by the chimney effect. Summer has joined the problem: as more Maine homes add heat pumps and air conditioning, the same leaks and thin insulation that waste heat in January waste cooling in July.
The good news is that this is a solved problem. Building science tells us exactly where the losses are and how to stop them. The Maine Uniform Building and Energy Code now sets some of the strongest insulation and air-tightness requirements Maine has ever had. And Efficiency Maine pays a substantial share of the cost of fixing existing homes.
The knowledge base
Start with the physics, finish with the code
This site is organized the way a good weatherization job is organized: understand how the house works first, then apply the rules, then spend the money wisely.
How the insulation envelope works
Conduction, convection, radiation, R-value, thermal bridging — and the single most important rule in cold-climate building: the air barrier and the insulation must be continuous, and they must touch.
Read the envelope guide →Every section of the box, in depth
Dedicated guides to each part of the envelope: attics & roofs, walls, basements & foundations, sound between rooms, and insulating between heating/cooling zones.
Start at the overview →BPI & ASHRAE, explained
The two organizations behind every number on this site — BPI's assessment standards and ASHRAE's ventilation, comfort, and heat-transfer science — decoded for homeowners.
Read the standards guide →The chimney (stack) effect
Your house behaves like a chimney: warm air exits the top, cold air is pulled in at the bottom, all winter long. It also runs in reverse in summer. Here's what it costs you and how to shut it down.
Read the stack effect guide →Why air sealing comes first
Building Performance Institute standards treat the house as a system. Insulation without air sealing is a wool sweater in the wind. Blower doors, attic bypasses, combustion safety, and the seal-then-insulate sequence.
Read the air sealing guide →MUBEC, explained
What the Maine Uniform Building and Energy Code is, the statutes behind it (10 M.R.S. §9721 et seq.), which model codes it adopts, where it applies, and who enforces it.
Read the MUBEC overview →New construction requirements
Foundations, walls, and attics for new Maine homes: the 2021 IECC prescriptive R-values, the blower door requirement, and the specific code sections that govern each assembly.
Read the new construction guide →Code-triggered insulation upgrades
When Maine law requires an existing home to be upgraded: additions, alterations, repairs, finished basements and attics, and change of occupancy — with citations to IECC Chapter 5 [RE] and the IEBC, section by section.
Read the triggered upgrades guide →Efficiency Maine rebates
How the Home Energy Savings Program pays for insulation and air sealing, how the income tiers work, why the work must be done by a Registered Vendor, and how financing fills the gap.
Read the rebates guide →Get it done
Ready for the work? We recommend two Maine installers — BRF Services and Maine Energy Services — for blower-door-verified air sealing, dense-pack walls, R-60 attics, and insulated basements, with rebates handled.
See our recommended installers →The short version
Five things every Maine homeowner should know
- Air leakage, not thin insulation, is usually the biggest loss. Warm air carries heat out of the house bodily. That's why BPI-based weatherization always seals the attic plane and basement before adding an inch of insulation. Why air sealing comes first → What a leak costs per year →
- The stack effect never takes a day off. The taller the house and the colder the day, the harder your home pumps heated air out through the attic. How the chimney effect works →
- MUBEC applies to your renovation, not just new houses. The Maine Uniform Building and Energy Code applies statewide to buildings constructed or renovated in Maine, and its Chapter 5 existing-building provisions decide when your project must be insulated to current code. When upgrades are required →
- New construction standards jumped on April 7, 2025. Maine moved from the 2015 codes to the 2021 editions: R-60 attics, continuous-insulation wall options, insulated basements, and a mandatory 3.0 ACH50 blower door test. The new numbers →
- Someone else will pay for a big share of the fix. Efficiency Maine's weatherization rebates cover a percentage of insulation and air sealing costs — the largest share for income-eligible households — when the work is done by a Registered Vendor. How the rebates work →
Not sure where your house stands?
A one-hour assessment with a blower door tells you more than a decade of guessing. Our recommended installers will show you where the leaks are, what the code expects, what the rebates cover, and what it will cost — in writing, with no obligation.
Schedule a Free Assessment