Summary: This article on InsulationMachines.net explains why sprayed cellulose insulation may not stay in wall cavities, focusing on differences between paper-based (gray, needs less water and higher pressure) and cardboard-based (brown, needs more water and lower pressure) cellulose. It shares a real jobsite example where switching brands fixed slumping issues, even with the same equipment settings. The guide advises adjusting spray tips and water pressure to match cellulose type, contacting manufacturers about recipe changes, and using poorly performing materials in attics instead of walls.
Article: Not all cellulose insulation is the same. Cellulose is made from recycled paper. When newspapers were common, cellulose was made primarily from news print and magazines. Today, those sources are becoming scarce, so cellulose manufacturers are now relying heavily on cardboard.
Cellulose composed of paper is gray in color. It requires less water to saturate. We suggest smaller tips (eg 20067) and higher water pressure (500psi) to get great penetration while using less water.
Cellulose composed of cardboard is brown in color. This needs more water saturation. So, we suggest smaller tips (eg 2101) and lower water pressure (250psi).
On this job site with BigTime Construction, they had two different cellulose brands which have a large paper content. We made sure that the following were checked before blowing:
- Blower air speed set so that the material was not bouncing off he wall.
- The feed gate was shut down to 6″ so there was not a lot of material.
- We used 20067 tips with water pressure set at 500 psi.
We struggled for the first 20 minutes. Material was sticking, but quickly slumped out of the cavity after a few minutes. We adjusted our distance from the wall and attempted to push material into the wall. That helped, but eventually it slumped out again.
This contractor was prepared. He had 150 bags from one brand and 150 bags from another. We started over with a fresh batch of cellulose from a different manufacturer. All settings remained the same. The material sprayed flawlessly. It filled the cavities with absolutely no slumping or falling out. The material on the floor remained ankle deep, providing a perfect amount of recycle.
Even though the first material did not perform well at all, it still works fine in the attic. This builder did not lose any money, he just changed up what materials worked better in the walls.
If you find yourself having difficulty with a certain brand of cellulose, not sticking in the wall, make sure to talk to the manufacturer. There may have been recent changes in the recipe at the factory. Check with your cellulose manufacturer to find out what they suggest. Also, feel free to call us for recommendations.
