The headline numbers
In 2026, approved insulation projects, attic, walls, basement, rim joists, receive 75 to 100% off through Mass Save. Standard-income households typically see 75 a 90% covered; income-eligible households can have the full cost covered.
What 'approved' means
The discount applies to work recommended in your no-cost home energy assessment and performed by a participating contractor. That's the whole path: assessment → written plan with incentives → discounted installation.
Why air sealing comes first
Air sealing is typically covered at 100%, and doing it before insulating makes the insulation perform as designed. Any good contractor will sequence it that way, be wary of one who doesn't.
What about bigger upgrades?
If your plan includes heat pumps, rebates reach up to $8,500 standard and up to $16,000 for income-eligible households, and the 0% HEAT Loan can finance the remainder. Insulation first, though, it makes any heating system's job smaller.