Commercial Wall and Knee Wall Insulation: Installation Instructions

This section provides info on “How to Install Insulation.”  It contains specific information on installation details for walls and knee walls that will assist with proper installation to meet commercial building codes and criteria for fiberglass and mineral wool batt insulation. Includes information on special situations as wells tips for insulating near pipes, along rim or band joists and around doors and windows.

Critical Details for Installing Insulation in Walls

Knee Walls - Installing Batt Insulation

Critical Details
knee wall insulation
  1. Verify insulation material is the correct width and R- value.
  2. Verify that top/bottom plates and a fire-rated rigid backing have been installed.
knee wall insulation
  1. Friction fit insulation between and parallel to the framing members in full contact with rigid backing, top and bottom plates.
  2. Ensure ends of insulation are flush and butted together.
knee walls
  1. When using kraft-faced batts: Fasten kraft face tabs of insulation to framing members. Note: no kraft paper overlapping required.
  2. When using vapor retarder with unfaced batts: Fasten vapor retarder to face of framing members once batts are installed.

Technical Tips for Installing Insulation in Walls

Limited Access and Special Situations

Limited Access and Special Situations are areas on exterior walls that may be easier to insulate before covering up. It is advisable to insulate these cavities first/before other wall cavities are insulated.

Stairs and Landings
installing insulation, limited access examples

Do: Install insulation to fill the cavity between conditioned and unconditioned space without gaps, voids, misalignments or compression.


Tubs and Showers
installing insulation, limited access

Do: For walls that will not have an interior finish and are separating conditioned and unconditioned spaces, wall cavities are insulated and an interior rigid air barrier is installed.


Fireplaces
installing insulation, limited access

Do: For walls that will not have the same interior finish and are separating conditioned and unconditioned spaces, wall cavities are insulated and an interior rigid air barrier is installed.

Narrow and Odd Cavities

Narrow Cavities
narrow, insulation

Do: Install insulation to fill the cavity between conditioned and unconditioned space without gaps, voids, misalignments or compression.


Odd Cavities
narrow, insulation

Do: Install insulation to fill the cavity between conditioned and unconditioned space without gaps, voids, misalignments or compression.


Corners
narrow, insulation

Do: Install insulation to fill the cavity between conditioned and unconditioned space without gaps, voids, misalignments or compression.


Ladder T (Interior/Exterior Wall Intersection)
narrow, insulation removed for demonstration only

Do: Install insulation to fill the cavity between conditioned and unconditioned space without gaps, voids, misalignments or compression.


Vapor Retarder
insulation, narrow

Do: Where a vapor retarder is required, cover the warm-in-winter side of the narrow space with vapor retarder facing.


Windows/Doors
insulation, narrow

Do: Air seal around windows and doors using backer rod, caulk or low expansion foam. Do not use fibrous insulation or air-permeable foam.

Obstructions and Obstacles

Boxes (Electrical, Smoke, CO, etc.)
insulation obstruction

Do: Cut and/or split insulation around wiring and boxes and place a piece of insulation behind the box.


Electrical Panels
obstruction - insulation removed for demonstration only

Do: Cut and/or split insulation around electrical panel wiring.


Wires (Electrical, Cable, Security, Low Voltage, etc.)
obstruction - insulation removed for demonstration only

Do: Cut and/or split insulation around wiring.


Dryer / Exhaust
insulation obstruction

Do: Cut and/or split insulation around exhaust fan boxes, ductwork, wiring and any support bracing.


Pipes and Vents (Water Supply, Plumbing Vents, Gas Lines, etc.)
obstruction - insulation removed for demonstration only

Do: Cut and/or split insulation around pipes.

Rim and Band Joists

House-to-Garage Band Joist
insulation how-to

Do: Ensure there is a complete air barrier between conditioned and unconditioned spaces.


House-to-Outside Band Joist
correct and incorrect images, installing insulation

Do: Ensure there is insulation between conditioned and unconditioned spaces.


Conditioned Crawl/Basement-to-Outside Rim Joist
insulation installation, rim

Do: Ensure there is a complete air barrier and insulation between conditioned and unconditioned spaces.

Standard Cavities (Faced)

Gaps
insulation installation detail

Do: Install insulation to fill the cavity completely between conditioned and unconditioned space without gaps.


Voids
insulation installation examples

Do: Install insulation to fill the cavity between conditioned and unconditioned space without voids.


Misalignment
insulation example

Do: Install insulation to fill the cavity between conditioned and unconditioned space without misalignments.


Compression
standard, insulation

Do: Install insulation to fill the cavity between conditioned and unconditioned space without compression. Split or slit batts around the wires.

Standard Cavities (Unfaced)

Gaps
standard cavities, correct and incorrect insulation examples

Do: Install insulation to fill the cavity completely between conditioned and unconditioned space without gaps.


Voids
standard cavities, correct and incorrect insulation examples

Do: Install insulation to fill the cavity between conditioned and unconditioned space without voids.


Misalignment
standard cavities, correct and incorrect insulation examples

Do: Install insulation to fill the cavity between conditioned and unconditioned space without misalignments.


Compression
standard cavities

Do: Install insulation to fill the cavity between conditioned and unconditioned space without compression.