4.1104.1 Stuffing Wall Cavities with Fiberglass Batts

Manufactured Housing Wall Insulation
Desired Outcome: 
Consistent thermal boundary Thermal boundary The separation between the interior and exterior environments of a building that slows heat flow and air barrier Air barrier The separation between the interior and exterior environments of a building that slows air flow to the point that no smoke movement is visible at 50 pascals of pressure difference across the boundary between the conditioned space and unconditioned space
Access wall cavities

If skirting overlaps siding, skirting will be detached to allow access to the wall cavity

Fasteners will be removed from the bottom of the siding, working upward until the siding can be pulled away from the framing approximately 6" without damaging the siding

Temporary fasteners will be installed near the bottom of the siding panels at the seams to prevent separation

If a subsheathing is present under the siding, access through the subsheathing will be required

Gain access to the wall cavity without damaging or separating the siding

Exterior wall cavity inspection

Wall cavities will be inspected for moisture damage, pest locations, and integrity of the wiring, and holes to the interior

Siding will be repaired as necessary

Location of belt rails, obstructions, and existing insulation will be identified

All interior surfaces of exterior walls will be inspected for loose paneling joints, occupant wall hangings, location of switches and outlets, and other wall obstructions

Objects will be removed from the interior surfaces of the walls being insulated

Interior paneling will be repaired as necessary

Prepare wall cavity for insulation

Prevent water leaks from occurring

Fiberglass batt installation tool (stuffer)

A sheet of polycarbonate, such as Lexan, will be cut to the following specifications to create a stuffer tool:

  • Approximately 1' x 8' x ¼" with a 5 degree bend 7' ½" from the bottom
  • All corners of the Lexan (polycarbonate) will be rounded and all edges will be sanded

Other clear sheet plastics will not be used due to a tendency to shatter under stress

Create a tool to install a fiberglass batt into the cavity

Ensure worker safety

Fiberglass batt installation

Thickness of the batt will fill the void without deforming siding or damaging structure

Fiberglass batts will fill the cavity (e.g., batt may be cut approximately 1" longer to ensure proper fill and allow for lap at the top)

Flexible membrane will have an appropriate perm rating Perm rating The measurement of a material's ability to allow the transfer of water vapor through the material for the region

Flexible membrane will be cut 2" wider than the cavity and approximately 1' longer than the batt

Stuffer tool, membrane, and fiberglass batt will be aligned for installation

Stuffer tool will be used to install the fiberglass batt and membrane at the same time

Excess fiberglass batt and membrane vapor retarder Vapor retarder A material that slows the passage of water vapor and contains a perm rating above 1 extending below the cavity will be rolled and tucked into the cavity

A poly-encased fiberglass batt may be used in place of the fiberglass batt and membrane assembly

The membrane will be installed in contact with the side of the wall that is compatible with the local climate zone

Maintain integrity of the batt

Aid in the installation process

Sub-sheathing patch and repair

Subsheathing will be patched or repaired as necessary

Ensure the integrity of the drainage plane


If skirting was removed, skirting will be reinstalled to shed water to the outside of the skirting

Siding will be reattached with new fasteners

Siding will be reattached without bulges or wrinkles

Ensure the integrity of the drainage plane

Return siding to existing conditions without damage

Onsite documentation
A dated receipt signed by the installer will be provided that includes:
  • Coverage area
  • Thickness
  • R-value

Document job completion to contract specifications

Confirm amount of insulation installed

Comply with 16 CFR 460.17