Wall Cavities and Ceilings

This truck is equipped to install either damp-spray or dense-pack cellulose.

The hopper that feeds material to the operator can be filled to the ceiling, providing enough material to last from 15 minutes to an hour, depending on the application.

Netting is stretched tight between framing members to minimize bulging of the cellulose.

Netting is fastened with a pneumatic upholstery stapler.

The closely spaced fasteners are driven at an angle just beyond the outer edges of the faces of framing members. This “inset stapling” helps draw the material taut and prevents the cellulose from pushing beyond the framing.

The tension of the netting against electrical boxes is enough to prevent them from filling with insulation when the cavities are packed; the netting will later be cut by the drywall crew.

A skilled installer can snugly fit the netting around joists, collar ties, and other obstructions. As long as the material is tight and securely stapled, small gaps won’t leak significant amounts of insulation as the cavities are blown full.

In complex areas, like the peak of this Queen Anne tower (below), netted dense-pack can be a cost-effective alternative to spray foam.

Wall cavities are filled first from the bottom to the midpoint of the wall.

Next, cavities are filled from the top back to the middle.

After a cavity is filled, the operator uses a remote control to momentarily turn off the blower, then quickly inserts the hose into the next cavity before switching it on again.

Filled cavities are compacted with an aluminum roller to avoid bulging drywall. A quick pass of the hand is enough to confirm that the insulation lies flush with the framing.

When filling rafter cavities, the usual insertion point is just above the top plate. The natural curvature of the longer hose required tends to direct the flow of insulation to one side of the cavity, so filling it uniformly requires a second pass with the curve facing the other way.

The hose is visible behind the netting in the photo at right.

A strip of netting between a top-plate nailer and the facing joist makes it possible to dense-pack this area of the band joist.

Netting stapled between the joist ends is filled with cellulose to form insulating and air-sealing “pillows”.

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