Retrofitting Sidewalls

Retrofitting Sidewalls


Many homes built prior to 1970 have no insulation in the wall cavities. GreenFiber recommends installing Insulation in sidewall cavities, the second major area of energy loss in most homes. The technique most commonly used is the two-hole, double blow method.

Wall Kit Needed to Install GreenFiber Insulation in a Sidewall Retrofit Application

  • 1″ wall nozzle
  • 1″ plastic, wood or foam plugs
  • Wall spackle (Exterior or Interior)

Suggested Tools for Installation

  • Stud finder
  • Putty knife
  • Utility knife
  • Drill
  • Two 1” drill bits
  • Dust masks
  • Hammer
  • Eye protection
  • Duct tape

Sidewall Preparation and Blowing Machine Guidelines

  • Examine both the inside and the outside of a home and inspect under sinks and around plumbing fixtures on outside walls for cracks and holes. Seal all cracks and holes with foam or caulk.
  • To ensure a safe installation, do not install insulation in stud runs where a heat-producing device such as an unprotected chimney, recessed light or fireplace may overheat. Inspect any recessed lights to ensure they are IC Rated for insulation contact.
  • Homes with balloon construction, where the wall cavities are open from the attic to the basement or crawl space, must have the tops and bottoms blocked off before blowing.
  • Place the blowing machine on level ground as close to your work area and electrical outlets as possible.  It is recommended that the homeowner use 100 ft (2 – 50 ft sections of hose for this install).
  • Spread plastic or canvas tarp under the blowing machine. This makes clean-up easier and helps keep foreign objects out of the hopper.
  • The most common reducer and plug size for the insulation blowing machine is 1”. Before drilling, check to ensure that the drill bit size matches the plugs and reducer size. Remove siding to drill holes through the sheathing or drill holes directly through the wood siding.
  • For a single story home, drill a hole between two studs approximately three feet up from the bottom of the wall. Drill a second hole approximately one foot down from the top of the wall in the same stud cavity. On a multi-story home, repeat these steps for each floor. Walls taller than 10 feet should have holes drilled every five feet making sure the top hole is approximately one foot from the top of the wall. Check locations of cold air returns to avoid drilling into them.
  • Probe all cavities using a plumb bob to determine the depth of the cavity and to discover any obstacles that might alter the flow of loose-fill cellulose insulation. In some older homes, the corners of the house may have diagonal bracing. Probe the walls at the corners to determine if your house has this type of framing. Drill additional holes in corners that have this bracing.
  • There are several blowing machines available through retailers with settings that adjust material flow depending on machine type. Be sure to read operating instructions thoroughly.

Sidewall Retrofit Installation Instructions

  • Insert the nozzle into the bottom hole first and turn on the blowing machine. Increasing back pressure causes the blower to strain, alerting the installer that the cavity is filled and ready for the next hole. Check to make sure the cavity is full. If not full, re-insert the nozzle and fill the cavity. Continue this process until each stud run is filled. Always start with the bottom hole first, and then the top hole.
  • Before filling the next hole check the end of the nozzle to make sure the material is not plugged. A wire from a coat hanger or a screw driver can be used to unplug the nozzle. If this method does not work remove the nozzle from the hose and clear the blocked material by closing the gate and blowing excess material into a trash bag. When hose is empty replace nozzle and continue blowing. Do not allow machine to run for an extended period of time without insulation coming out of the hose.
  • Place plugs into holes after cavities have been filled. Recess plugs 1/16 to 1/8 inch past the face of the plaster, drywall or siding. Cover the plugs with an interior or exterior spackle as needed. If the spackle dries and leaves a depression apply another coat of spackle. Allow spackle to dry before sanding and painting.
  • When the job is finished, blow excess material into a trash can to empty the machine of insulation.
  • Always return the blowing machine to the retail location from which it was rented. Be sure to comply with all aspects of the rental agreement.