In an HVAC system, ducts are necessary to provide heating, ventilation, and air conditioning solutions from the HVAC equipment to the target rooms. Generally, all ducts pass through garages, basements, attics, and crawlspaces in a building. These areas are known as unconditioned space since they are not considered part of the living area and hence, are usually not heated or cooled.
The practice of having ducts run through unconditioned space is not an energy efficient one. Leakage of air from ducts and the difference in temperature between the surrounding air and duct air are two main reasons for energy loss. This loss may account for as much as 25% of energy needed for cooling and heating. In addition, dust, moisture, and bacteria from unconditioned spaces can enter the ducts and be transported to the living areas (conditioned spaces). This decreases the overall quality of air circulating within the building.
Installing ductwork within the conditioned space can provide large energy savings. This process involves studying the existing system and designing a new system to minimise energy loss. The easiest way to do this is to integrate the ducts into the ceiling. This may not always be possible due to space constraints. In such situations, ducts may be enclosed in partitions or screens, or as part of a tray ceiling, which also adds volume to the room. In other areas, ducts can run through closets and floor framework.
Putting ducts within the conditioned space has an added advantage as it saves the cost and labour involved in insulating the ducts themselves. Sealing the ducts is still necessary, though. This prevents most cases of air leakage. In case air does leak out, it remains within the conditioned space. Overall, placing ducts within the conditioned space improves the functioning of the HVAC system.
The initial cost involved in fitting ducts within the conditioned space is quite high. This is because certain structures may need to be built, to house the ducts. Duct placement involves creating a design plan and incorporating the ducts requires the services of an HVAC contractor.
The high installation costs are balanced by the low operational costs. Leakage of air from ducts is restricted to the conditioned space, which minimizes energy loss. It is estimated that this installation can decrease energy bills by up to 35%.