Do I Need to Remove Fiberglass Insulation Before Adding Blown-in Insulation?

Adding blown-in insulation to your attic space is a popular way to improve energy efficiency and reduce heating and cooling costs. But what if you already have fiberglass insulation? Do you need to remove it before adding the new material, or can it stay in place?

Adding loose-fill insulation can significantly improve your attic's efficiency and thus your energy savings, but careful preparation is key. Before you get started, assess your current insulation and address air sealing and proper ventilation. With a little work, you’ll create a cozy, energy-efficient home for years to come.

Things to Consider

• Condition of Existing Insulation: If the fiberglass insulation is in good shape—dry, fluffy, and evenly distributed—it may not need to be removed; however, attic insulation that's compressed, damp, or moldy should be replaced.
• Pests or Damage: Evidence of rodents, insects, or other pests may indicate contamination. In such cases, removing and cleaning the affected areas is critical for health and safety.
• Air Gaps and Energy Efficiency: Adding a blow-in insulation over pre-existing insulation can help fill gaps, enhance the air barrier, and improve thermal performance, provided the fiberglass layer isn’t obstructing proper coverage.
• Structural Issues: If the attic floor, ceiling joists, or other structural elements are damaged, these need attention before adding additional insulation.
• Ventilation and Moisture Control: Poor attic ventilation can lead to excess moisture buildup, compromising both the existing and new insulation. Get rid of wet insulation and address any water damage, mold growth, and ventilation issues before proceeding.

How to Remove Old Insulation (if You Need to)

If your fiberglass insulation is damaged or contaminated, grab your protective gear and follow these steps to safely remove it.

You'll Need

• Dust mask or respirator rated for fiberglass particles
• Heavy-duty gloves and protective clothing
• Trash bags or contractor-grade disposal bags
• Shop vac with a HEPA filter
• Flashlight for visibility

1. Check for Contaminants

• Inspect for rodent droppings, growth of mold, or damp spots. If contaminated insulation is present, take extra precautions such as sealing waste in heavy-duty bags and using a disinfectant spray where necessary.
• If you aren't sure, it's better to have a professional insulation contractor check for asbestos insulation. It can still be found in old homes and needs special insulation removal methods.