High Performance Wall Assemblies

Jun 7, 2024

High Performance Wall Assemblies

Overview

  • High performance walls are more than just insulation.
  • Requirements:
    • Handle bulk water.
    • Ability to dry if wet.
    • Airtight.
    • Prevent or manage condensation and water vapor.

Materials in New vs. Older Homes

  • *Older Homes:
    • Built with stronger materials (old growth lumber).
    • Partly insulated; dried easily.
  • *New Homes:
    • Built with fast-growing timber, OSB, plywood, paper face gypsum.
    • Highly insulated but more moisture-sensitive.
    • Drying requires heat transfer, slowed by insulation leading to mold and rot.

Common Themes in Wall Assemblies

  • Relatively vapor open to allow drying.
  • Least expensive options use materials from home improvement stores.

Wall Assembly 1: Standard

  • Materials:
    • OSB or Plywood
    • Tyvek home wrap (needs air sealing tape)
    • Gypsum board, 2x6 framed wall with Rockwool Comfort bat
    • Vertical furring strips (rain screen battens)
  • Advantages/Disadvantages:
    • Plywood has higher hydro buffer capacity than OSB.

Wall Assembly 2: Zip System Sheathing

  • Materials:
    • Zip system sheathing
    • Integrated weather barrier
    • Air sealing zip tape
    • Same rain screen battens
  • Advantages:
    • Easier weatherproofing, increased air tightness, reduced labor costs.

Wall Assembly 3: Cavity Insulation and Rigid Insulation

  • Location: Pacific Northwest
  • Materials:
    • Combination of Rockwool products
    • Self-adhered weather barrier (Delta vent sa)
    • 2x6 frame wall with Rockwool Comfort bat, plywood sheathing
    • Rockwool Comfort board 80 to prevent thermal bridging
    • Rain screen system

Wall Assembly 4: Perfect Wall

  • Concept:
    • No interior insulation.
    • 5-inch layer of Rockwool Comfort board 80 for exterior insulation.
  • Advantages:
    • Prevents thermal bridging.
    • Maximum drying, reduces condensation potential.
    • Easy installation of plumbing and electrical conduits.

Key Insights

  • Lifespan of a home depends on its ability to dry.
  • Vapor-permeable materials and rain screens help prevent mold, wood rot, and poor indoor air quality.