The Four Control Layers
Introduce bulk water, air, vapor, and thermal control as the core taxonomy. Continuity and verification are central to performance—a layer that stops at a transition isn't a layer.
How this fits in the series
Builds on:
P5 (system interactions)
Leads to:
P7–P10 (specific control layers and assemblies)
Core concepts and execution implications
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Each control layer has a distinct function.
- Can label each layer in common assemblies.
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Continuity beats material selection.
- Can prioritize connections at transitions and penetrations.
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Verification differs by control type.
- Can plan testing/inspection appropriate to each layer.
Connections
- Performance framework: G — Controls (G1–G8)
- Cross-series: A6 Materials & Labor (control layer continuity depends on trade coordination)
- Explore in Performance Framework →
What good looks like
For any enclosure element (wall, roof, slab edge, window opening), we want:
- Clear definition of each layer: water control, air control, vapor control, thermal control.
- Continuity of each layer around the whole building (not just in the "field" of the wall).
- Alignment so layers support each other instead of creating traps (thermal + air + vapor risk).
- Buildability: details people can execute consistently.
Explore in PF: Each bullet maps to a G-column node in the framework—trace from Water Control (G4) outward to see how continuity requirements propagate.
Control-layer mapping template
For any assembly or transition, fill in each layer. If you can't name it, that's the risk.
| Water control layer | ___ |
| Air control layer | ___ |
| Vapor control layer | ___ |
| Thermal control layer | ___ |
| Most likely continuity break | ___ |
Use this at every transition: roof-to-wall, window opening, foundation-to-wall, penetrations. The blank spots tell you where to focus inspection and detailing.
Where things go wrong
Four-layer thinking catches problems early. Common discontinuities: water layer missing shingle-lap logic at flashings, air layer "Swiss cheese" (small holes add up), vapor + temperature mismatch (cold surface can't dry), and thermal bypass (insulation not continuous at rim joists, slab edges, window bucks). Examples:
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Window opening with great WRB but leaky air barrier
Bulk water stays out, but air leakage drives moisture into the opening; comfort complaints and hidden condensation show up later.
Layer miss: air control discontinuity
Field check: blower door with smoke at window perimeter; verify air seal is continuous around all four sides -
Slab edge: "warm floor" isn't just comfort
Missing thermal control at the slab edge creates cold surfaces, condensation risk, and occupant discomfort—often read as "drafty."
Layer miss: thermal discontinuity
Field check: thermal scan slab perimeter in heating season; verify insulation is continuous at foundation-to-wall transition
Explore in PF: Each "layer miss" is a broken edge in the G-column chain. Use the framework explorer to see which downstream outcomes each discontinuity triggers.