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.

Rolls of old fiberglass insulation.
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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.
Empty attic with a skylight and pink insulation.
If you hear or smell something unexpected, be sure to check the attic for signs of a pest, or worse, a full-blown infestation. Credit: MediaProduction / Getty Images

2. Remove the Insulation

  • Carefully roll or lift fiberglass batt insulation, starting at one corner. For loose fill insulation, use the shop vac to suction the layer of insulation material into bags.
  • Avoid stirring up dust by handling the material gently.
  • If you're unsure or have health concerns, consider using an attic insulation removal service.

3. Dispose of Properly

Check local regulations for disposal of fiberglass insulation. Many areas consider it a hazardous material and require it to be taken to a specific landfill or recycling facility.

4. Inspect the Attic

Once the old insulation is gone, inspect every inch of the attic space or ceiling crawl space for air leaks, water damage, or moisture issues that need to be addressed before adding new insulation.

Man caulks around window in an attic.
Before you re-insulate your attic space, pay close attention to ventilation and air leaks. Credit: Fokusiert / Getty Images

The Importance of Air Sealing Your Attic

Before adding new insulation—whether you're removing old materials or not—take the time to seal air leaks in your attic. Roof leaks and gaps around light fixtures, plumbing vents, and ductwork can allow warm air to escape, reducing the effectiveness of your insulation. Sealing these leaks ensures your home stays comfortable and energy-efficient while preventing issues like ice dams and drafts.

Is there such a thing as too much insulation?

While more insulation generally improves energy efficiency, it’s possible to overdo it. Adding excessive layers can compress the vapor barrier or block the ridge vents which can trap water vapor and affect indoor air quality. An insulated space needs some air flow. Excessive materials can reduce effectiveness, or block ventilation pathways, leading to moisture buildup. Follow your local building codes and the Department of Energy’s guidelines for recommended insulation levels (measured in R-value) based on your climate zone. This ensures you’re adding just the right amount for maximum performance without unintended consequences.