This advanced text is intended for the building professions: the engineer, architect or technical specialist involved in the design, construction, operation, maintenance, repair, and renovation of buildings. The focus is on predicting and understanding the heat, air, and moisture response of the building enclosure, i.e., walls, windows, roofs, below-grade construction. The text moves from the fundamental physics to more practical applications for all climate regions, including worked example calculations of heat flow, vapor diffusion and air leakage condensation through building enclosures.