3.1001.2 Chase Capping

Penetrations and Chases
Desired Outcome: 
Chase capped to prevent air leakage and moisture movement between the attic and conditioned space

An inspection will be conducted for mold, water leaks, and water damage before sealing a chase

Repairs will be completed before work begins

Repair moisture-related issues

Standard chase (interior walls covered with drywall or plaster)

Entire opening will be spanned with rigid material Rigid material Drywall, oriented strand board, duct board, cardboard, or any other stiff product that may support the load of insulation while serving as a durable air barrier

Material will be cut to fit and fastened as required

Reduce opening to what can be sealed with sealant

Non-standard chase (interior walls covered with wood or paneling)

Material will be used that can be exposed to the interior of the house and meet the flame and smoke spread indexes as required in IRC IRC International Residential Code

Prevent a fire hazard


Support material Support material Typically, wooden strips that provide support over holes greater than 24" in size for less rigid air barrier materials will be installed for spans wider than 24", except when air barrier Air barrier The separation between the interior and exterior environments of a building that slows air flow to the point that no smoke movement is visible at 50 pascals of pressure difference across the boundary material is rated to span greater distance under load (e.g., wind, insulation)

Ensure seal stays in place and does not sag

Joint seal

Continuous seal will be installed around seams, cracks, joints, edges, penetrations, and connections

Provide airtight, durable seal that does not move, bend, or sag

Adjacent framing

All remaining gaps at the top of the chase will be sealed

Ensure airtight seal from one finished side of the chase to the other