Performance of thermal distribution systems in large commercial buildings.

A field study was carried out to establish the performance of five thermal distribution systems in four large commercial buildings. They were standard single-duct or dual-duct constant air volume (CAV) system and variable air volume (VAV) systems, serving buildings with floor area greater the 2000 m2. Reports the duct air leakage. The ELAs ranged from 0.7 to 12.9 cm2/m3 of duct surface area, and from 0.1 to 7.7 cm2/m2 of floor area. The results showed that air leakage in large commercial duct system had significant variation between systems and between system sections even within the same thermal distribution system. The systems were revealed to be much leakier than the standard ASHRAE measure for 'unsealed ducts'. However, thermal losses from supply ducts due to conduction were significant and comparable to those induced by air leakage. States that significant potential for energy savings exists in large commercial buildings by attention to detail in the use of duct sealing and duct insulation.