Rigid Insulation

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

Select rigid insulation that:

is a class II vapor retarder

is between 0.5 and 2.0 lb/ft3 in density and has a flame spread/smoke development index equal to or less than 25/450 when tested in accordance with ASTM E84 or UL 723

Remove any existing insulation or vapor barrier materials and protrusions from installation area

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

Seal each cavity airtight around the perimeter of the rigid insulation

If foam is no more than 3 1/4" thick and the space is not permanently habitable no thermal barrier is required

If foam is thicker than 3 1/4", doesn't meet the flame and smoke index, or is of less than 0.5 lb/ft3 density, or the space is permanently habitable, separate foam from the subspace with a suitable thermal barrier covering or coating as indicated in manufacturer's specifications and applicable building code

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

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