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Cellulose insulation is made from treated paper fibers, whereas fiberglass insulation is made from tiny glass fibers and sand. Both materials are reasonably effective insulators, and neither act as air barriers.
The R-value for fiberglass batts ranges from 3.1–3.4 per inch of thickness. For loose-fill fiberglass insulation in an attic, the R-value is 2.2–4.3 per inch and for the wall is 3.7—4.3 per inch. Batt’s fiberglass insulation is excellent for walls and can be used for attics. Loose-fill fiberglass is the opposite.
Closed-cell spray foam has an R-value of roughly 6.5 per inch while open-cell spray foam has an R-value of 3.5 per inch. The R-value of fiberglass is significantly lower at around 2.2 per inch. In addition, fiberglass insulation loses R-value over time while spray foam insulation maintains its effectiveness.
