Thermal and Moisture Protection
Insulation
Know the product families - batt, blown-in, rigid foam board, and spray polyurethane - and their R-values per inch. Continuous insulation outside the framing defeats thermal bridging at studs, which batt alone cannot do. Georgia is largely IECC climate zone 3A, mixed-humid, so envelope values come from the locally adopted code edition.
Four different barriers
An air barrier controls air movement and must be continuous and sealed at penetrations, top plates, and rim joists. A vapor retarder limits vapor diffusion and belongs on the warm side of the assembly. A weather-resistive barrier sheds bulk water behind the cladding. Flashing integrates with the WRB at openings and transitions. Questions routinely conflate these four.
Ventilation and details
Attics need about 1/150 of the vented ceiling area, or 1/300 with balanced intake and exhaust and a vapor retarder. Crawl spaces and floors over garages need insulation plus air sealing, and exterior rigid insulation must be protected at grade.
Traps
Putting a strong vapor retarder on the wrong side of the wall; calling housewrap a vapor barrier; omitting air sealing at penetrations; and creating a wall that cannot dry in either direction.
Rule of thumb: every assembly should be able to dry in at least one direction - never sandwich a wall between two impermeable layers.