MH - Blown Insulation in Roof-Over Construction

Detail ID 4.0103.13
Attic Floors - Unconditioned Attics
Desired Outcome

Continuous, safe, and compliant thermal barrier installation that protects integrity of interior surfaces, client health, and roof-over weather protection

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


  • MH
Specification Objective

Verify that installation area is free of:

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

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

Ensure space can be safely insulated

  • MH
Specification Objective

Select loose fill fiberglass insulation that has a flame spread and smoke development index of 25/450 or less when tested in accordance with ASTM E84 or UL 723

Select fire safe insulation

  • MH
Specification Objective

Select sealants that:

are compatible with their intended surfaces

allow for differential expansion and contraction between dissimilar materials

meet the requirements of the applicable fire safety code (e.g., thermal or ignition barriers)

are low volatile organic compound (VOC) sealants for use inside the pressure boundary that meet independent testing and verification protocols

Select safe, durable, and effective sealants

  • MH
Specification Objective

Setup a dust control enclosure for all interior access locations that limits insulation and construction dust exposure to the occupant and occupant belongings

Prevent occupant exposure to construction dust

  • MH
Specification Objective

If roof-over attic is large enough for safe physical access, perform all work from the exterior of the original attic by means of access through the roof-over roof or gables

If roof-over attic space is not large enough for safe physical access, install insulation in original attic from the interior of the dwelling and install insulation in the roof-over attic from the roof or gable of the roof over attic

At a minimum, access each end cavity of the original attic to install insulation

Safely access both attics

  • MH
Specification Objective

Fill each end cavity of the original attic to capacity

Add additional insulation to meet prescribed R-value to either the original attic or on top of the original roof if sufficient space is available or both if necessary to meet the prescribed R-value

If additional insulation is installed on top of the original roof follow the applicable Single Family SWS for attic insulation

Continuous thermal barrier of appropriate R-value

  • MH
Specification Objective

Install closure system over all interior access holes that is airtight, durable, and aesthetically pleasing

Install closure system over all holes in the original roof that is airtight and durable

Install closure system over access holes in the roof-over attic with a durable, weatherproof, and pest resistant closure

Airtight, durable, and aesthetic interior access closure. Weathertight, durable, and pest-resistant exterior access closure

  • MH
Specification Objective

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

Comply with 16 CFR 460.17 and document contract compliance