Most residential construction is built with a "t-shirt" level of protection, but on this high-performance home project, we’re using the full "Sweater Approach."

By wrapping the entire roof in continuous insulation (CI), the system reaches R51 and virtually eliminates thermal bridging through the rafters. If you’ve ever wondered whether exterior roof insulation is worth the extra labor for a vapor-open assembly, this breakdown covers it in detail.

Building Envelope Strategy

• The Air Barrier: Zip System sheathing (taped and rolled) for a primary air seal.
• The "Sweater": 3 inches of Rockwool Comfortboard 80 continuous insulation.
• The Rainscreen: 2x4 battens creating a 1.5" ventilation channel.
• The Outer Shell: A second layer of sheathing for the final roofing system.

Key Concepts Covered

• Building Science: Why R51 and continuous insulation improve efficiency and durability.
• Roof Framing Math: Using BuildCalc to determine sleeper bevels and saw tilts (49.62°).
• Structural Fasteners: Why Simpson Strong-Tie SWD screws are ideal over mineral wool.
• Compressibility Test: Testing Rockwool rigidity under 185 lbs of load.

Video Timeline

• 0:00 - Cross section insulation detail
• 1:57 - Soffit venting
• 3:19 - Starting the process
• 4:03 - Insulation knife
• 4:38 - Order of operations
• 6:53 - Cutting valley pieces
• 11:59 - Installing Rockwool
• 13:47 - Compressibility test
• 14:20 - Valley installation
• 16:17 - Sheathing over insulation
• 21:00 - Fastening battens

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Company: Pioneer Builders