We prioritize thermal insulation over sound absorption, so we traveled to Lowe’s and bought Rockwool Comfortbatt.
This improves the sound absorption but decreases the amount of airgap and therefore Rockwool has stated Safe N Sound has a lower R-Value of 3.9. Thickness is the difference between the two products, as the Safe N Sound is 3″ thick, but has the same amount of material and is therefore denser. Rockwool also makes a similar but different product, branded Rockwool Safe N Sound, which is available at Home Depot. This insulation is not sold at Home Depot, only Lowe’s. We purchased the 3.5 inch thick product, hence a total R-Value of 15. Rockwool Comfortbatt has an R-Value of 4.3 per inch of thickness. That’s good enough for us! Per the Rockwool website, “Living close to an airport, the noise you hear inside your house is reduced by 40 percent if your roof is insulated with ROCKWOOL stone wool.”
At that rating “loud speech is not audible” across rooms. Rockwool has a sound transmission class (STC) of 45 in a standard residential. From the spinning machine the wool enters a chamber where small quantities of resin binder and mineral oil are added to lock the strands together and make them water repellent.
The melt is directed onto a series of rotating wheels where it is spun into wool. The rocks are graded and crushed to a suitable size, mixed with coke and slags, then melted in a furnace at a temperature of 1500 ☌. The insulation is made of stone wool, described as: “a natural material formed from volcanic diabase rock.
After a couple sessions with it we ditched that gear and there was no unreasonable skin irritation. Technically it can make you itchy if it touches skin, so when we started we put on gloves, long sleeves, and a dust mask. Rockwool was very easy to work with – it’s lightweight and cuts with a handsaw. Our insulation choice, Rockwool Comfortbatt, does double duty – thermal resistance for temperature as well as sound absorption. We elected forego MLV and have no regrets, as the van is plenty quiet for us. The heavier it is, the more sound it blocks – yet, the heavier it is, the worse it is for our van’s miles per gallon. The main purposes, and downside, of this product is its weight. Optional: For extreme sound protection, a layer of Mass Loaded Vinyl (MLV) can be added on top of the sound deadening butyl material sound to block sounds.