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Fiberglass is considered a favorite garage insulation choice due to its combination of affordability, ease of installation, and overall effectiveness. Fiberglass provides good thermal resistance, helping regulate garage temperatures and minimize heat transfer. Additionally, fiberglass is moisture-resistant, reducing the risk of mold or mildew formation.

Yes, you can install insulation behind drywall yourself, but only if your walls are not finished. If your studs are exposed, installing fiberglass insulation in roll or batt form is very straightforward and just requires a few tools and some safety equipment. If your walls are already finished and you’re looking to add insulation, it’s better to hire a professional, as you’ll likely need blown-in insulation, which can be dangerous to work with and a challenge to get into the proper areas in your wall voids.

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.

While there are many different kinds of insulation, spray foam, blown-in, foam board, and batt and roll are the four types you’re most likely to see. That doesn’t mean they’re alike, though. Each one varies drastically in terms of cost, materials used, and how they’re installed—not to mention, how well they limit heat transfer.