Wall design hot humid, passive cooling
Most wall installation guidelines seem to assume buildings will be conditioned continuously. But suppose in zones 2A, 3A or even 4A you had home operators contrary enough to avoid use of AC for as much of the year as possible — but who may rely on AC for a few particularly hot and humid weeks of the year. I hear such people still exist.
State of the art wall design for hot humid seems to desire the vapor retarder or barrier external to the insulation and the framing, so that the wall can dry to the interior, aided by the dehumidification potential of the … AC. But what if the conditioning unit is not being operated for much of the 7 months of the year? And consider that some of the best temperatures for passive cooling during the long shoulder seasons may be accompanied by consistently high humidity. Perhaps under those conditions it’s a moot point, since humidity would be high both sides (though sometimes higher inside or out depending on time of day), and drying might not occur regardless of where the vapor barrier is. But is there any reason to believe an external vapor barrier would actually increase wall moisture issues in (mostly) non-conditioned buildings?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part