Continuous insulation outside the wall framing — eliminates thermal bridging at studs

Description

Continuous insulation (rigid foam or mineral wool) outside the wall sheathing breaks the thermal bridge created by wood studs. Effective R-value of the assembly: nominal cavity R + CI R-value × ~0.9 (small loss at fastener penetrations). Typical strategies: 1-2 in of XPS or polyiso outside the sheathing; rainscreen + cladding outside that. Limit is determined by climate-zone vapor-control requirements + fastener-shear limits for the cladding. Long fasteners reach through the foam into the framing.

Why this exists

A 2×6 wall with R-23 cavity insulation but no CI performs at about R-15 effective because of stud bridging. Add R-10 CI and you reach R-25 effective. CI is one of the highest-leverage envelope improvements for the cost; it's also the easiest way to comply with energy codes that target whole-assembly R-values.

Categories

Source

Solver enforcement

Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.

Related directives

• Continuous load path from roof to foundation · HUD RSDG §2.4
• Residential structural reliability targets 1-in-100 to 1-in-1000 annual probability of failure · HUD RSDG §2.5
• Residential floor live load: 40 psf minimum (30 psf sleeping rooms) · HUD RSDG §3.4
• Wind load design uses ASCE 7 basic wind speed for the locality · HUD RSDG §3.6
• Ground snow load for Virginia: 25 psf eastern, up to 40 psf western mountains · HUD RSDG §3.7