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Building enclosure control layers · Lesson 3 of 4

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.

13 min · 11 slides · 11 questions

All lessons in this module
Slide 1 of 11

The four-layer pen test

This course's four-layer pen test traces each layer on the drawings without lifting the pen; a place where the pen must lift is a break.

BSC's parapet insight asks the designer to connect the water, air, vapor and thermal layers of the roof to the wall.

Seven steps follow: gather, trace four layers, mark transitions, record.

The four-layer pen testSeven steps in a column: gather the documents; trace the water line; trace the air line; trace the vapor line; trace the thermal line; a decision box asking whether any line breaks, with the answer to flag it for the designer of record; mark every transition and penetration; record the result. Each trace step shows its line style: solid blue, dashed green, dotted teal, amber hatch.The four-layer pen test1Gather the documentsWall, roof and parapet details,products and the code edition2Trace the WATER lineRoof membrane up the parapet,under the coping, to the wall3Trace the AIR lineRoof air layer to wall air layer,with no gap at the deck4Trace the VAPOR lineOne layer, on the side the climatecalls for, not one on each side5Trace the THERMAL lineRoof insulation to wall insulation;mark where structure interruptsDoes any line break?If yes, flag it for the designer of record.Do not fix it yourself.6Mark every transitionand penetration, and whodetails each one7Record the resultPass or fail for each layer, thesources, and open questionsExtends the rain-layer pen test to all four layers.

Seven steps in a column: gather the documents; trace the water, air, vapor and thermal lines, each with its line style; a decision box asking whether any line breaks, answered by flagging it for the designer of record; mark every transition and penetration; record the result.

1
Gather the wall, roof and parapet details, the specified products and the code edition
2
Trace the water line: membrane up the parapet, under the coping, to the wall
3
Trace the air line: roof air layer to wall air layer, with no gap at the deck
4
Trace the vapor line: one layer, on the side the climate calls for
5
Trace the thermal line: roof insulation to wall insulation, marking interruptions
6
Mark every transition and penetration and who details it
7
Record pass or fail for each layer, the sources and the open questions
This course's method, built on BSC's rule that each layer of the roof connects to the same layer of the wall.

Sources

Videos for this lesson

What this video shows: Building Science Corporation on keeping each control layer continuous across openings and intersections, and on one material serving more than one layer. Checked against the video's description.

Video: Cup of Joe - Continuity of Control Layers by BuildingScience-com Corporation, on YouTube. Chosen from the video's published description.

Glossary

Pen test
Tracing a control layer on the drawings without lifting the pen. This course extends it to all four layers; a break in the line is a break in the layer.
Transition
A place where one control layer changes material or direction, such as roof membrane to wall membrane at a parapet. The 2021 IECC asks that joints and seams at transitions between materials be sealed.
Designer of record
The architect or engineer responsible for the enclosure design. Breaks found in a trace are questions for them, not for the fabricator to resolve.
Dew point
The temperature at which air at a given humidity reaches saturation. The AFS Envelope tool computes it with the Magnus formula and flags interfaces at or below it as places indoor air could condense.