Air distribution describes how conditioned air is delivered to and returned from occupied spaces within a building. Proper air distribution ensures even temperatures, adequate ventilation, correct pressurization, and occupant comfort throughout all areas.
Key elements include: supply air outlets (registers, grilles, diffusers) that introduce conditioned air into rooms, return air grilles that draw air back to the air handler, ductwork that connects everything, and the air handler or furnace that moves and conditions the air. Supply air velocity, throw (how far the air travels before mixing with room air), and spread (width of the air pattern) are designed to achieve proper room air mixing.
Common air distribution problems include: cold/hot spots from poor throw or coverage, noise from high air velocity, pressure imbalances causing door drafts, and inadequate return air capacity. Return air is especially critical — insufficient return air causes negative pressure in rooms with supply registers but no return, leading to infiltration, comfort issues, and sometimes back-drafting of combustion appliances.