A timber-frame wall needs coordinated thermal, air and moisture control layers. Insulation properties alone do not describe studs, joints and sheathing.
Layer functions
Mark structure, insulation, air barrier and rain protection in section. One material may serve several roles, but each role must be established for the specific application.
Thermal non-uniformity
Studs, headers and fixings change heat transfer. Dividing insulation thickness by λ is not a complete frame-wall calculation.
Moisture and drying
Consider initial timber moisture, construction rain and drying after enclosure. Select vapour control for climate and the complete assembly, not a universal membrane rule.
Airtightness and installation
Trace air-barrier continuity at floors, windows and penetrations. A service cavity can reduce punctures; inspect concealed joints before lining.
Durability and mistakes
Do not enclose wet layers without assessment. Changing sheathing or cladding requires renewed moisture, fire and structural review; no fire-resistance class is assigned here.
| Item | Parameter | Check / result |
|---|---|---|
| Frame | Loads and non-uniformity | Calculation |
| Barrier | Joints and penetrations | Inspection |
| Moisture | Condition before enclosure | Check |
What this means for your project
Request a complete assembly with junction details and moisture checks. Do not assess a frame wall solely by insulation thickness.
Sources and scope of review
- PNNL / Building America — Moisture control for residential buildings
- ISO 6946:2017 — Thermal resistance and transmittance
Related reading
- Vapour Permeability and Vapour Control: Avoiding Common Confusion
- Moisture in Assemblies: Diffusion, Convection and Leaks
- Roof Airtight Layer: Common Construction Errors