Dense Packing Cellulose: On Site Training

CaptureThis article introduces the steps and materials involved in dense packing cellulose into an unfinished wall cavity. This project was filmed at a house retrofit in Flint, Michigan. This rebuild will showcase the highest in energy-efficiency standards. This is a collaborative project between Mott University and the Department of Energy.

Tools and Materials You Will Need

  • Cellulose: Use standard cellulose material. There is no need to use stabilized cellulose as no water is used during this process.
  • Wall Fabric: This polyester fabric is ideal for this project. With 2,000 sq ft of wall, only one 10’x375’ bag was required. Click here to see the wall fabric product.
  • Hammer Tacker and/or Pneumatic Stapler: You will use plenty of staples on this project. The staples were place about 1-1/2” apart to provide a tight covering to prevent the bulging of material. If you use a pneumatic stapler (recommended), use a furniture-type of stapler. A trim or roofing stapler will not work.
  • Foam: This project required urethane foam to be used around the windows, doors and smaller cracks.
  • Fiberglass batt: You will find cavities that are far smaller than your hose. Have some fiberglass, on hand, to stuff into those cavities.
  • 3” pvc pipe: Some contractors prefer to use a 2” vinyl hose. For this project, we attached a 3’ section of 3” pvc pipe to the end of our hose. This works well in giving you more control.

Step One (Day One)

The first day on the project was dedicated to preparing the job.

  • Foaming the windows and doors.
  • Filling Small cavities with fiberglass.
  • Installing the Wall Fabric: You will notice that the fabric is attached to the top plate and draped around the room. Stilts make this very easy! Staple the fabric with 1-1/2” intervals and tug firmly on the fabric to stretch it into place. Don’t stretch it very hard. You will find that a snug stretch is all that is necessary. Don’t cut out the electric outlets until the cavities have been filled with the cellulose.

Step Two (Day Two)

A project, this size, only requires a couple of days. The first day is prep work. The second day is filling the cavities with cellulose.

  • Set the dense packing pressure on your machine to 3.5 PSI. That is the required pressure to prevent the cellulose from settling and gives the proper density for the most efficient vapor penetration.
  • Cut a vertical slit halfway up the wall cavity and insert hose. Start by packing the cellulose into the upper part of the cavity. As the cellulose packs into the cavity, you will transition to sliding the hose into the bottom of the cavity. It takes about 30 seconds to fill a 2”x4” wall – 8’ high.
  • Some contractors like to tape the slits shut. This is optional.


If you have any questions or need tech support on dense packing with cellulose, do not hesitate to call (even if you have not purchased anything from us). We are dedicated to helping insulation contractors around the world!