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Blown-in insulation works, but only for unfinished attics. Also, it isn’t the longest-lasting nor the most effective option. For better options, look into spray foam insulation or natural fiber batts. They typically have a longer lifespan, better heat resistance, and stronger sound-proof abilities. Spray foam insulation costs about $1.25 to $1.50 per square foot, but can go up to more than $4 per square foot. Fiber batt pricing varies depending on the material.

The best type of insulation for your home depends on your specific needs, climate, and the area you are insulating. For new construction, structural insulated panels are a highly energy-efficient option that is easy to install during the building process. In very warm climates, reflective insulation can be a cost-effective choice. For cold climates, fiberglass is an excellent option due to its high R-value and resistance to settling over time. Spray foam works well in humid environments because of its moisture-resistant properties. For standard attics, loose-fill, spray foam, or blown-in insulation are all suitable options.

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.

The life span of insulation is between 20 and 100 years. At that time, existing insulation can fall victim to gravity, resulting in compression, which reduces its insulating protection or R-value. If you can't simply add more insulation over the existing material, removing the old to increase the effectiveness of the new can reduce your energy bills and make the project worth the time and money investment.