Labels:bulletin board | hakham | sky | window OCR: Pressure Differences Drive Moisture illustrated on the previous slide vapor driven into walls through pressure diff Terences Vapor pressure difference in air masses drive molecular moisture into the wall For example warm humid air mass has moisture it and theref fore has high vapor oressure air can not hold much moisture has low pressure difference between air masses pressure that drives mo lecular moisture into wall assemb Molecular moisture penetration or permeation is measured in "perms" Permeation through building mat erial expressed perms which represents an actual am ount moisture mo lecularh passing through certain period time certain area under certain vapor pressure differ ence Air driven into building simply by the pressure of air movement this can wind internal mechanical ystems ...
