Building enclosure control layers
The four control layers of a building enclosure (water, air, vapor and thermal) and their order, the 2021 IECC air-leakage limits and BSC vapor retarder classes with their units, a four-layer trace of a parapet, and the defects and verification that follow.
4 lessons · about 49 min · 12 diagrams · 2 videos
Version 1.0.0
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Lesson 1 · 10 min · 11 slides · 8 questions
Building enclosure control layers: principles and terminology
The four control layers of a building enclosure (water, air, vapor and thermal), the order BSC gives them, where they can sit, why continuity is the rule at the roof-to-wall junction, and where AFS sheet metal fits beside them.
You will be able to: Name the four control layers and their order of importance, say where they sit and why each must be continuous from roof to wall, and state who designs, supplies and verifies them.
Not startedStart →Lesson 2 · 15 min · 12 slides · 13 questions
Building enclosure control layers: materials, standards and design constraints
The 2021 IECC air-leakage limits by tier with units and test pressure, how a failed whole-building test is handled, BSC's vapor retarder classes and climate guidance, thermal bridging categories, and how a specification writes continuity and QA.
You will be able to: Read the air-leakage criteria for a material, an assembly and a whole building with their units and test pressure, place the vapor retarder classes, and say what thermal bridging adds, each with its edition and source.
Not startedStart →Lesson 3 · 13 min · 11 slides · 11 questions
Building enclosure control layers: methods and worked application
A seven-step method for tracing water, air, vapor and thermal layers across a roof-to-wall transition, then three worked checks: a whole-building leakage test against the 2021 IECC limit, a vapor retarder class, and an indoor dew point.
You will be able to: Run the four-layer pen test on a parapet detail, mark transitions and penetrations, and work a whole-building air-leakage check, a vapor class check and an indoor dew point with every input and unit written down.
Not startedStart →Lesson 4 · 11 min · 12 slides · 8 questions
Building enclosure control layers: defects, verification and case study
Six defects the four-layer trace catches at a parapet, how a mock-up, field observations, inspection and a whole-building test verify the layers, and a constructed case that fails its test and its own drawings.
You will be able to: Recognize six common control-layer defects at a parapet, say how mock-ups, field QA and whole-building tests verify the layers and who performs them, and walk a constructed case from test result to evidence packet.
Not startedStart →
Practical task
Build a control-layer review packet for one roof-to-wall parapet detail (your own, or a project detail you may use): trace the four layers, check the numbers the detail depends on, and list the questions for the designer of record.
Hand in
- A decision rationale: which detail you reviewed, the code edition and specification sections it is built under, and who is the designer of record, each named
- A marked-up sketch of the parapet section with four lines (water, air, vapor, thermal) in the line styles of this module, every break and every transition marked
- An assumptions sheet with units: envelope area, test pressure, perm ratings and the source of each (drawing, data sheet, code or assumed)
- A checklist of the trace steps with pass or fail for each layer, and one worked check from the module (a leakage limit, a vapor class or an indoor dew point) with the arithmetic shown
- A defect analysis: one break you found, which of the six defects it resembles, which layer it affects, and the question you would send the designer of record
Rubric
| Criterion | Meets the standard when |
|---|---|
| Documents | The edition of the code and the specification sections are named, and values are labelled as code, manufacturer, guide or assumed. |
| Trace | All four lines are traced from roof to wall without lifting the pen, and each break and transition is marked. |
| Numbers | Each number carries its unit and test pressure (cfm/ft2 at 75 Pa, perm) and a source, and the arithmetic can be repeated. |
| Roles | Breaks are written as questions for the designer of record; nothing in the packet tells the fabricator to fix a layer, and nothing calls a metal coping an air or vapor layer. |
| Vapor and thermal | There is one vapor layer on the side the climate calls for, and the thermal line shows where structure or the parapet interrupts it. |
| Safety | The packet does not require anyone to go on a roof; testing and inspection are assigned to qualified agents. |