(Effective Until July 1, 2010.)
WAC 51-51-0806   Section R806 -- Roof ventilation.  


R806.4 Conditioned attic assemblies. This section is not adopted.



[Statutory Authority: RCW 19.27.074, 19.27.020, and chapters 19.27 and 34.05 RCW. 07-01-090, § 51-51-0806, filed 12/19/06, effective 7/1/07.]






(Effective July 1, 2010.)
WAC 51-51-0806   Section R806 -- Roof ventilation.  


R806.4 Unvented attic assemblies. Unvented attic assemblies (spaces between the ceiling joists of the top story and the roof rafters) shall be permitted if all of the following conditions are met:

     1. The unvented attic space is completely contained within the building thermal envelope.

     2. No interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly.

     3. Where wood shingles or shakes are used, a minimum 1/4-inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing.

     4. Any air-impermeable insulation shall be a vapor retarder, or shall have a vapor retarder coating or covering in direct contact with the underside of the insulation.

     5. Either items a, b or c below shall be met, depending on the air permeability of the insulation directly under the structural roof sheathing.

     a. Air-impermeable insulation only. Insulation shall be applied in direct contact to the underside of the structural roof sheathing.

     b. Air-permeable insulation only. In addition to the air-permeable insulation installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing as specified per Washington climate zone for condensation control.

     i. Climate Zone #1 - R-10 minimum rigid board or air-impermeable insulation R-value.

     ii. Climate Zone #2 - R-25 minimum rigid board or air-impermeable insulation R-value.

     c. Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct contact to the underside of the structural roof sheathing as specified per Washington climate zone for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.

     i. Climate Zone #1 - R-10 minimum rigid board or air-impermeable insulation R-value.

     ii. Climate Zone #2 - R-25 minimum rigid board or air-impermeable insulation R-value.



[Statutory Authority: RCW 19.27.031 and 19.27.074. 10-03-098, § 51-51-0806, filed 1/20/10, effective 7/1/10. Statutory Authority: RCW 19.27.074, 19.27.020, and chapters 19.27 and 34.05 RCW. 07-01-090, § 51-51-0806, filed 12/19/06, effective 7/1/07.]