Building Envelope, Roofing, and Thermal Moisture Protection
Envelope principles
Understand the four control layers: water, air, vapor, and thermal. Know the difference between a weather-resistive barrier, an air barrier, and a vapor retarder, and where each belongs in wall assemblies. Traps: placing a vapor retarder on both sides of a wall, and confusing permeance ratings with thickness.
Water management
Study drainage plane, flashing sequence (roof to wall, window head and sill), weep systems, and the principle that water must always have a path out. Kick-out flashing at roof-wall intersections is a classic exam trap.
Roofing
Compare low-slope systems (TPO, EPDM, modified bitumen, built-up) and steep-slope systems (asphalt shingle, metal, tile). Know slope thresholds: low slope is generally below 3:12, and shingles require at least 2:12 with underlayment. Understand insulation above versus below deck and the effect on condensation.
Thermal and moisture
Know R-value, U-factor, thermal bridging, and continuous insulation. Understand dew point location and how interior versus exterior insulation changes condensation risk. Vapor drive is from warm to cold, so in cold climates the vapor retarder goes on the warm side.
Worked example
A wall with R-13 cavity insulation and R-5 continuous insulation has a total R of 18, but thermal bridging through studs reduces effective performance. Use the parallel-path or zone method rather than adding nominal values.
Rule of thumb
Shingle roofs need at least 2:12 slope; below that, use a low-slope membrane system.