How to Use Recycled Cardboard for Home Insulation

How to Use Recycled Cardboard for Home Insulation

Insulating your home can help reduce your energy bills and make your rooms more comfortable, but traditional insulation like fiberglass batts or spray foam can be expensive. An eco-friendly and cost-effective alternative is to use recycled cardboard for insulation. Here is a complete guide on how to use cardboard for insulating your home.

Gathering and Preparing Cardboard

The first step is gathering a sufficient amount of cardboard and making sure it is properly prepared before installing it as insulation. Here are some tips:

  • Source clean, dry cardboard – Focus on collecting cardboard boxes, product packaging, shipping boxes, etc. Avoid cardboard that is greasy, contaminated, or has a wax coating.

  • Remove tape, staples, and labels – This will allow the cardboard to lie flat. You can easily scrape off tape with a putty knife.

  • Break down boxes – Flatten all boxes so the cardboard pieces lie flat. This will make them easier to install.

  • Cut into consistent sizes – Using a utility knife or scissors, cut the cardboard into pieces that are easy to handle. Strips 12-24 inches wide work well.

  • Store in a dry area – Keep the cardboard dry before installation. Wet cardboard will be ineffective insulation.

  • Collect a significant quantity – Estimate how much insulation you need for the project and gather enough cardboard ahead of time. Err on the side of more.

Choosing a Location

Determine what area of your home you want to insulate with cardboard. Some common locations include:

  • Attic floor
  • Exterior walls
  • Basement walls
  • Crawl spaces

Focus on portions of your home that are under-insulated or lacking insulation altogether. Cardboard works well for unfinished spaces like attics and basements.

Prepping the Installation Area

Before installing the cardboard, prep the space by doing the following:

  • Clear away existing insulation – Remove any old or existing insulation materials from the space first.

  • Clean and dry the surface – Use a broom to sweep away dust, dirt, and debris. Cardboard should only touch clean, dry surfaces.

  • Seal air gaps and penetrations – With caulk or spray foam, fill any cracks, holes, or penetrations that allow air flow. This helps the insulation work effectively.

  • Install a vapor barrier – In exterior walls and ceilings, install a vapor barrier like plastic sheeting to prevent moisture issues.

Installing the Cardboard Insulation

With the space prepped, you’re ready to install the cardboard insulation:

  • Cut pieces to fit – Measure the space and cut cardboard pieces to size using a utility knife. Leave a 1/2 inch gap between pieces.

  • Place pieces tightly together – Without compressing the cardboard, fit pieces tightly together. Eliminate gaps between pieces and around edges.

  • Fill voids completely – Make sure the entire area is filled with cardboard without any empty spaces. Use smaller pieces to fill irregular voids.

  • Alternate direction between layers – When adding multiple layers, orient each layer perpendicular to the last to maximize coverage.

  • Add at least 3-4 layers – For sufficient insulation, install at least 3-4 layers of cardboard or until you reach the desired thickness.

Finishing Touches

To complete the project:

  • Secure cardboard in place – Use twine, mesh, lath strips, or cap nails to hold cardboard securely against walls and ceilings.

  • Seal exterior edges – Along exterior edges, apply caulk or spray foam to seal the insulation and prevent air infiltration.

  • Install covering – Protect cardboard insulation from wildlife, moisture, and sunlight by installing coverings like drywall, rigid foam boards, or wood boards.

  • Get building inspection – Check your local building codes and have the completed installation inspected if required.

Safety Tips

When working with recycled cardboard:

  • Wear gloves, long sleeves, and a dust mask to avoid skin irritation and dust inhalation.

  • Use a sharp utility knife carefully when cutting cardboard to avoid injuries.

  • Work in ventilated areas and sanitize cardboard if mildew or mold is present.

  • Do not compress cardboard tightly as this can reduce insulation effectiveness.

  • Keep insulation at least 3 inches from heat sources like chimneys and appliance vents.

Pros and Cons of Cardboard Insulation

Cardboard insulation has advantages and disadvantages:


  • Renewable and recyclable resource
  • Inexpensive and easily accessible
  • Simple DIY installation
  • Effective insulator against cold and heat


  • Can attract pests and mold if wet
  • Lower R-value than fiberglass or foam insulation
  • Compresses over time and loses insulation capacity
  • Requires protective coverings
  • Not fire resistant

Overall, recycled cardboard insulation is an eco-friendly and cost-effective insulation option in the right circumstances. With some simple precautions, it can help increase your home’s energy efficiency.