Distribution effectiveness evaluates how uniformly conditioned air reaches all areas within a space, measuring temperature and velocity variation across occupied zones. Poor distribution causes comfort complaints, temperature stratification, and reduced ventilation effectiveness. Distribution effectiveness combines factors including ductwork design, register selection, and space geometry.
Assessment Methods
Distribution effectiveness is quantified by measuring temperature variation, with effective systems maintaining variation under 2°C (3.6°F) between zones. Velocity profiles near supply registers should decrease from 0.5 m/s to under 0.1 m/s within 1-2 meters. ASHRAE 113 provides standard methods using thermal imaging and anemometer surveys across the occupied zone. Poor distribution often correlates with 15-25% higher energy consumption due to larger temperature setpoint differentials.
Optimization Techniques
Improving distribution effectiveness involves proper ductwork sizing using static regain methods, balanced return-air pathways, and optimal register placement. Low-velocity displacement ventilation and stratified mixing strategies enhance distribution uniformity. Computational fluid dynamics (CFD) modeling helps predict distribution patterns in complex spaces. Well-designed distribution reduces energy consumption by 10-20% while improving occupant comfort and reducing demand for local heating and cooling adjustments.