4.1303.3 Insulation of Floor Cavity with Spray Foam Material

Manufactured Housing Floor Cavity Insulation
Desired Outcome: 
Installation of a consistent thermal boundary Thermal boundary The separation between the interior and exterior environments of a building that slows heat flow between conditioned and unconditioned space that reduces heat flow

Insulation will be installed in accordance with recommended R-value

Insulate to prescribed R-value for the climate zone

Work assessment

Ensure complete accessibility of floor cavity

Ensure work area is clean, safe, and ready to accept insulation


All floor areas will be open and accessible for spray foam application

Any openings in the subfloor larger than ¼" will be covered with appropriate materials

Insulation dams or end blockers will be installed where needed

All surfaces where spray foam is applied will be clean, dry, and free of contamination and degradation

Substrate surfaces will be wiped, blown, or vacuumed to be free of excessive dust and dirt

Grease and oil will be removed using appropriate cleaners or solvents

Moisture content of all wood substrate materials will be below 19%; if tested at or above this percent of moisture, insulating the floor will be deferred until moisture level is corrected

Clean floor cavities

Remove all remnants of previous insulation and bottom board

Prepare all substrate surfaces for the application of spray foam


Insulation will be installed to prescribed R-value in accordance with manufacturer specifications

In accordance with manufacturer specifications, spray foam will be applied to desired thickness using the maximum pass thickness onto subfloor between floor joists and all rim/band joists

Rim/band joist will be sealed

When desired, underside of joists will be covered with spray foam to provide a layer of continuous insulation

Each cavity will be insulated to specified R-value

Insulation must be in contact with subfloor

Insulation will not have gaps or voids

Ducts and water lines will be insulated for climate conditions

Insulate and seal floors

Eliminate voids

Minimize conductive and convective heat transfer across the floor system

Ensure durability


Insulation will be installed in accordance with manufacturer specifications

Flame spread index of selected materials will not exceed 25 with an accompanying smoke-developed index not to exceed 450 when tested in accordance with ASTM ASTM ASTM International, www.astm.org E 84 or UL UL Underwriters Laboratories 723

Flame spread index of foam insulation will not exceed 75 and a smoke- developed index of no more than 450 when tested in the maximum thickness intended for use in accordance with ASTM ASTM ASTM International, www.astm.org E 84 or UL UL Underwriters Laboratories 723

Foam insulation will be separated from the interior of the building by an approved thermal barrier at minimum 1/2" gypsum or a material that is tested in accordance with the acceptance criteria of both the Temperature Transmission Fire Test and the Integrity Fire Test of NFPA NFPA National Fire Protection Association, www.nfpa.org 275

Ensure durability

Ensure worker safety

Ensure proper installation

Fire safety will be maintained

Fire protection

Spray foam will be separated from the occupied space of the building with a 15-minute thermal barrier (typically 15/32" sheathing, 1/2" gypsum board, or approved thermal barrier coating) or as approved by ASTM ASTM ASTM International, www.astm.org E84 requirements

Spray foam designed to be used as a fire block does not require a thermal barrier installed prior to application

Provide necessary fire protection for combustible spray foam insulation

Occupant education

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