Which is better for a 2x4 wall?

The Johns Manville R-13. Its batts are sized for 3.5-inch cavities. The Knauf roll is 6.25 inches thick and is meant for 2x6 framing.

Which gives more R-value?

The Knauf EcoRoll at R-19 versus R-13 for the Johns Manville. That is about 46% more thermal resistance per square foot.

Which is better for soundproofing between floors?

Both reduce sound transmission. The Knauf is explicitly marketed for between-floor and interior-wall use, and its denser mineral wool helps with low-frequency noise.

Is the Knauf worth extra money?

Only if you have 2x6 cavities or want the less-itchy mineral wool and recycled content. For 2x4 walls, the R-13 does the job for less.

Does either contain formaldehyde?

No. Knauf is GREENGUARD Gold certified formaldehyde-free, and Johns Manville uses a formaldehyde-free binder.

Can I use the Johns Manville in exterior walls?

Yes. Its kraft facing is made for moisture control in exterior walls, and it works in wood, engineered wood and steel framing.

Knauf EcoRoll R-19 Insulation Roll vs Johns Manville R-13 Kraft-Faced Insulation

Buy the Knauf EcoRoll R-19 for 2x6 walls and between-floor sound control; buy the Johns Manville R-13 for standard 2x4 exterior walls. The Knauf gives more R-value per inch and a formaldehyde-free, less-itchy mineral wool roll. The Johns Manville is the cheaper, widely stocked batt for 3.5-inch cavities. No prices were provided for either product, so compare current store prices on Deal.ai before buying.

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