R-30 insulation is better for higher thermal resistance, but whether it’s "better" depends on the application. R-30 is much thicker and suited for areas like attics or floors in cold climates, where more insulation is required. R-13, on the other hand, is thinner and works well for 2x4 walls or milder climates where less insulation is sufficient. Choosing between R-13 and R-30 depends on the area being insulated and the climate. For example, R-30 provides more insulation but may not fit everywhere in your home.

You do not always need to remove old insulation before adding new. If the existing insulation is in good condition—not wet, physically damaged, moldy, or infested with pests—you can add new insulation directly on top of it for a compounding effect. You can also mix different types, such as adding blown-in insulation around existing fiberglass batts.

However, removal is recommended if the old insulation is compromised by water damage or pests. You should also remove it if you plan to install a different type of insulation, like switching from roll or batt insulation to spray foam. If the existing insulation is very old or damaged, you will likely get more benefit from removing it and starting fresh.

We do not recommend fiberglass insulation for soundproofing purposes, especially if you are working on a room that’s part of your living space. Fiberglass insulation is dangerous, and the installation process is hazardous. It is also harmful to the environment. When there are so many newer, healthier non-fiberglass alternatives in the market, the lower cost of fiberglass insulation simply doesn’t justify the harm and danger it poses.

When it comes to fiberglass insulation versus foam board, there are a few notable differences, both aesthetically and functionally. Fiberglass insulation is soft and flexible, meaning it can be squeezed into tight spaces more easily than foam board. Fiberglass insulation also has a higher R-value, making it a better pick for colder climates. However, foam board insulation can resist moisture and pest damage much better than fiberglass.