What insulation should I use for a framed wall.

For typical wall cavities, here are the top options:

Spray Foam Insulation (Closed-cell)Best for: highest R-value (about R-6.5 to R-7 per inch), air sealing.

Cons: expensive, needs professional install, can be tricky to repair later.

Fiberglass Batt Insulation Best for: cheap, easy DIY install, decent R-value (~R-3.2 to R-3.8 per inch).Cons: must fit perfectly to avoid gaps, can irritate skin/airways.

Mineral Wool (Rockwool)Best for: fire resistance, soundproofing, water resistance, easy fit.

Cons: a bit more expensive than fiberglass, slightly lower R-value (~R-4.0 to R-4.3 per inch).

Blown-in CelluloseBest for: filling irregular cavities, eco-friendliness (recycled paper), good air sealing.

Cons: can settle over time if not installed properly.If you're looking for the absolute best balance for a typical wall cavity — Rockwool batts are often a favorite among builders now.If you want maximum R-value and don't mind cost — closed-cell spray foam is the king.