1. Follow work order for air-sealing sill

• Sill should be air-sealed at seams and corners with adhesive or foam prior to insulating

• See the Air seal Basement or Crawl Walls when air sealing is called for.

2. Install insulation

• Install one of the following insulation types

2a. Fiberglass batts

• Select batt insulation that has a class II vapor retarder facing and that has a flame spread and smoke development index of 25/450 or less

• Cut batt to fit sill with no gaps up against the framing.

• Insulation must maintain full contact to ensure a continuous thermal boundary.

• Do not compress batt insulation

2b. 2-part foam

• Install 2-part foam up to 3 1/4" thick. may also be used for air-sealing and insulation.

• See SDS material safety for restrictions of use.

• The Sill is the one location on a home where foam plastics can be installed without an ignition barrier but shall meet the conditions of 4.0401.1f.

• Foam is not thicker than 3 1/4" thick, listed as either ASTM E84 or UL 723, Flame spread of 25 or less and Smoke Developed Index of 450 or less.

2c. Pin and drape

• Folding foundation insulation to insulate sill.

• Fiberglass blanket can be notched and folded into sill, attach to joists with staples.

• Edges of blanket must be sealed ensuring no insulation is exposed.

2d. Rigid foam

• Use non-corroding materials to seal the seams around the insulation with adhesive.

3. Worst Case Draft Test

• Conduct a worst case draft test to verify Category I, II, and III appliances are venting before leaving the job for the day.

• Testing shall be recorded using the Utah WAP Worst Case Draft Test form.

4. Install Insulation Certificate

• A dated insulation certificate signed by the installer will be posted on a wall in the space where the furnace is located, a utility room or an approved location inside the building.

• The certificate must include:

  1. Installed insulation type

  2. Coverage area

  3. Installed thickness

  4. Installed R-value

  5. Manufacturer product name

  6. Manufacturer supplied material density

  7. Flame Spread rate

  8. Smoke Development index