Get asked about insulation all the time. Rockwool or fiberglass. Here’s my take after installing both for years.
Fiberglass – The Standard
Pink stuff. Been around forever. Cheap. Works fine. Itchy to install. Wear long sleeves and a mask.
R-value is decent. R-13 for standard walls, R-30+ for attics. Does the job.
Doesn’t burn but melts at high temps. Not a fire barrier really.
Rockwool – The Upgrade
Stone wool. Denser than fiberglass. Doesn’t itch as bad. Costs more but not outrageously.
Better soundproofing. This is the main reason I use it in interior walls. Bedroom next to laundry room? Rockwool.
Fire resistant to like 2000 degrees. Actually used as fire stopping.
Water Behavior
Fiberglass absorbs water and stays wet. Promotes mold. Bad in damp locations.
Rockwool repels water. Dries out if it gets wet. Better for basements and bathrooms.
What I Install
Fiberglass in attics where cost matters and moisture isn’t an issue. Big space, lots of material, budget matters.
Rockwool in walls for soundproofing. Between floors. Around HVAC for fire safety. Anywhere moisture might happen.
Bottom Line
Fiberglass is fine for most uses. Rockwool is better but costs more. Choose based on location and budget.
