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PDFWAC 51-11R-40241

Table R402.4.1.1Air barrier and insulation installation.

TABLE R402.4.1.1
General requirements
A continuous air barrier shall be installed in the building envelope.
Air-permeable insulation shall not be used as a sealing material.
Exterior thermal envelope contains a continuous air barrier.
Breaks or joints in the air barrier shall be sealed.
Cavity insulation installation
All cavities in the thermal envelope shall be filled with insulation. The density of the insulation shall be at the manufacturers' product recommendation and said density shall be maintained for all volume of each cavity. Batt type insulation will show no voids or gaps and maintain an even density for the entire cavity. Batt insulation shall be installed in the recommended cavity depth. Where an obstruction in the cavity due to services, blocking, bracing or other obstruction exists, the batt product will be cut to fit the remaining depth of the cavity. Where the batt is cut around obstructions, loose fill insulation shall be placed to fill any surface or concealed voids, and at the manufacturers' specified density. Where faced batt is used, the installation tabs must be stapled to the face of the stud. There shall be no compression to the batt at the edges of the cavity due to inset stapling installation tabs.
Insulation that upon installation readily conforms to available space shall be installed filling the entire cavity and within the manufacturers' density recommendation.
The air barrier in any dropped ceiling/soffit shall be aligned with the insulation and any gaps in the air barrier sealed.
The insulation in any dropped ceiling/soffit shall be aligned with the air barrier.
Access openings, drop down stair or knee wall doors to unconditioned attic spaces shall be sealed.
Batt insulation installed in attic roof assemblies may be compressed at exterior wall lines to allow for required attic ventilation.
The junction of the foundation and sill plate shall be sealed. The junction of the top plate and top of exterior walls shall be sealed. Knee walls shall be sealed.
Cavities within corners and headers of frame walls shall be insulated by completely filling the cavity with a material having a thermal resistance of R-3 per inch minimum. 
Exterior thermal envelope insulation for framed walls shall be installed in substantial contact and continuous alignment with the air barrier.
Windows, skylights and doors
The space between window/door jambs and framing and skylights and framing shall be sealed.
Rim joists
Rim joists shall include the air barrier.
Rim joists shall be insulated.
Floors (including above garage and cantilevered floors)
The air barrier shall be installed at any exposed edge of insulation.
Floor framing cavity insulation shall be installed to maintain permanent contact with the underside of subfloor decking or floor framing cavity insulation shall be permitted to be in contact with the topside of sheathing or continuous insulation installed on the underside of floor framing and extend from the bottom to the top of all perimeter floor framing members.
Crawl space walls
Exposed earth in unvented crawl spaces shall be covered with a Class I, black vapor retarder with overlapping joints taped.
Where provided instead of floor insulation, insulation shall be permanently attached to the crawlspace walls.
Shafts, penetrations
Duct shafts, utility penetrations, and flue shafts opening to exterior or unconditioned space shall be sealed.
Narrow cavities
Batts in narrow cavities shall be cut to fit and installed to the correct density without any voids or gaps or compression, or narrow cavities shall be filled by insulation that on installation readily conforms to the available cavity space.
Garage separation
Air sealing shall be provided between the garage and conditioned spaces.
Recessed lighting
Recessed light fixtures installed in the building thermal envelope shall be sealed to the finished surface.
Recessed light fixtures installed in the building thermal envelope shall be air tight and IC rated.
Plumbing and wiring
Batt insulation shall be cut neatly to fit around wiring and plumbing in exterior walls. There shall be no voids or gaps or compression where cut to fit. Insulation that on installation readily conforms to available space shall extend behind piping and wiring.
Shower/tub on exterior wall
The air barrier installed at exterior walls adjacent to showers and tubs shall separate the wall from the showers and tubs.
Exterior walls adjacent to showers and tubs shall be insulated.
Electrical/phone box on exterior wall
The air barrier shall be installed behind electrical or communication boxes or air sealed boxes shall be installed.
HVAC register boots
HVAC supply and return register boots shall be sealed to the subfloor, wall covering or ceiling penetrated by the boot.
Concealed sprinklers
When required to be sealed, concealed fire sprinklers shall only be sealed in a manner that is recommended by the manufacturer. Caulking or other adhesive sealants shall not be used to fill voids between fire sprinkler cover plates and walls or ceilings.
IC = insulation contact.
a In addition, inspection of log walls shall be in accordance with the provisions of ICC-400.
[Statutory Authority: RCW 19.27A.020, 19.27A.045, 19.27A.160 and chapter 19.27 RCW. WSR 20-01-047, § 51-11R-40241, filed 12/9/19, effective 7/1/20. Statutory Authority: RCW 19.27A.020, 19.27A.045, 19.27A.160, and 19.27.074. WSR 16-02-127, § 51-11R-40241, filed 1/6/16, effective 7/1/16. Statutory Authority: RCW 19.27A.020, 19.27A.045 and chapters 19.27 and 34.05 RCW. WSR 13-04-055, § 51-11R-40241, filed 2/1/13, effective 7/1/13.]
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