The best soundproof insulation is generally the one of the common soundproofing materials that is the most dense. Mineral wool is a product made of rock and is very dense. People typically think of pink fiberglass insulation with they thing about insulation for walls or ceilings. Fiberglass insulation does work very well however mineral wool is typically cheaper per pound. A similar density of fiberglass is more expensive. R ratings are similar for the same thickness and do not vary much with changes in density. However, when you compare insulation values available for 2×4 depth framing you’ll find R11 & R13 in fiberglass options but you can get R15 in mineral wool. For 2×6 framing the difference is even greater. R19 is the fiberglass option while R23 is available in mineral wool. What’s also great about mineral wool insulation for soundproofing is the benefits in fire resistance and it’s ability to shed water in the event of a broken pipe or other water issue.
In a scientific test of various types of insulation titled Summary Report For Consortium On Fire Resistance And Sound Insulation Of Floors: Sound Transmission Class And Impact Insulation Class Results, one of the primary findings was:
“Performance is most influenced by the sum of the masses per unit area of the floor and ceiling layers”
Mineral wool insulation is generally substantially more dense than fiberglass insulation making it an ideal sound blocking material. The glass fibers in fiberglass insulation are much longer and allow it to hold together better. This allows for a less dense product that still performs well in it’s insulation properties. Mineral wool fibers are much shorter and require it to be packed more densely to maintain its entanglement to the other fibers. The result is more mass per unit area compared to fiberglass.
Roxul is the best soundproof insulation brand on the market currently. Their Roxul Safe’n’Sound product offers the best value for the money. It’s affordable, has the best frequency rating, and is designed for indoor residential use. While Safe’n’Sound is great, their other products are also excellent in their ability to reduce noise penetration. Safe’n’Sound is meant for interior walls, ceilings, and floors but not exterior walls, attics, or crawlspaces. It’s ideal for soundproofing existing interior walls that don’t already have insulation.
If you’re going to be going to the trouble to remove existing sheetrock or are in the middle of new construction and want to get the job done right the first time, mineral wool is the best route to go. Roxul Rockboard acoustic mineral wool leads the pack amongst mineral wool manufacturers however most mineral wool products are also impressive.
Don’t forget to consider a quality sound-absorbing drywall product and Green Glue Noiseproofing Compound. The combination of this and mineral wool should prove quite impressive at reducing sound transmission.
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