Spray foam and blown-in cellulose are two of the most common insulation choices in older New England homes. Neither is “better” everywhere. The right one depends on where it’s going.
Closed-cell spray foam
Sprayed as a liquid that expands and hardens, closed-cell foam insulates and air-seals in a single step. It has a high R-value per inch, so it suits tight spaces, and it resists moisture.
Best for: rooflines, rim joists, knee walls and crawl space walls.
Trade-off: it generally costs more than cellulose.
Blown-in cellulose
Made from recycled paper fiber treated for fire and pest resistance, cellulose is blown into attics or dense-packed into closed wall cavities through small access holes, which are patched afterward.
Best for: attic floors and older walls that were built without insulation.
Trade-off: it has a lower R-value per inch, and it needs air sealing first because it slows heat but doesn’t stop air.
Side by side
| Closed-cell spray foam | Blown-in cellulose | |
|---|---|---|
| Air sealing | Seals as it is applied | Needs separate air sealing |
| R-value per inch | Higher | Lower |
| Typical cost | Higher | Lower |
| Moisture | Resists moisture | Should be kept dry |
| Good fit | Rooflines, rim joists, crawl spaces | Attics, older wall cavities |
Why many homes use both
A common approach is to air seal the attic floor and add cellulose on top, then use spray foam at the rim joist and any rooflines or tight spots. Each material goes where it performs best.
How to choose
A thermal audit shows where your home is actually losing heat, so you pay for the work that matters. See our spray foam and blown-in cellulose pages, or book your free thermal audit or call 413-524-2415.