Knee Wall - Batt Insulation

Detail ID 4.0104.2
Topic
Attics
Subtopic
Attic Knee Walls
Desired Outcome

Continuous, contiguous, safe, and compliant thermal boundary that prevents air movement @ 50 Pascals

SF Single Family Site-Built Housing
MH Manufactured Housing
MF Multifamily Housing

Specifications

  • SF
  • MH
  • MF
Specification Objective

Verify that installation area is free of:

active water leaks, fuel leaks (i.e., gas, oil, propane), and pest intrusions

energized knob and tube wiring

uncovered electrical junctions

improperly terminated devices (ventilation fans, dryers, plumbing stacks, condensate lines, combustion appliance flues/chimneys, etc.)

unshielded high-temperature devices (non-IC rated recessed lights, chimneys, flues, vents, etc.) unless they are zero clearance devices

insulation escape openings

Verify that installation area is:

intact, able to support insulation weight, and air sealed (including blockers under kneewalls in alignment with the interior side of the kneewall)

Prepare for safe, effective, and airtight installation of dense-packed insulation

  • SF
  • MH
  • MF
Specification Objective

Select insulation that has a flame spread and smoke development index of 25/450 or less and backing material for attics used for storage with a smoke development index of 450 or less when tested in accordance with ASTM E84 or UL 723

Select fire safe materials

  • SF
  • MH
  • MF
Specification Objective

Remove any existing insulation or vapor barrier materials from installation area

Prevent condensation

  • SF
  • MH
  • MF
Specification Objective

Install batt insulation to prescribed R-value in every joist bay in full contact with the air barrier and all sides of the ceiling cavity without gaps, voids, compressions, or misalignments

If batt contains a facing material, install it in contact with the conditioned space

Continuous and contiguous thermal boundary

  • SF
  • MH
  • MF
Specification Objective

Install airtight backing material in full contact with the existing cavity insulation

Secure backing material using mechanical fasteners that penetrate the sub framing a minimum of 1"

Installation must have a minimum of a 30-year service life

Airtight, durable insulation cavity

  • SF
  • MH
  • MF
Specification Objective

Separate all foam products from living space with a thermal barrier material (e.g., 1/2" gypsum wallboard) as specified by applicable building code

If attic is used only for the service of utilities, foam will be separated from the attic space using a suitable ignition barrier covering or coating according to manufacturer's specifications

If attic is used for storage or occupancy, spray foam will be separated from the attic space using a thermal barrier material (e.g., 1/2" gypsum wallboard) as specified by applicable building code and manufacturer specifications

If code requirements are unclear, consult local code officials for clarification

Minimize ignition and combustion potential

  • SF
  • MH
  • MF
Specification Objective

Post a dated receipt signed by the installer that minimally includes: Installed insulation type, coverage area, installed thickness, and installed R-value

Comply with 16 CFR 460.17 and document contract compliance