Air Duct Design, Efficiency & Energy Savings

Air Distribution Institute (ADI), initiated a duct efficiency study conducted at Texas A&M University which began in the spring of 2004. ADI, TXU Electric Delivery, ASHRAE and Lennox Industries co-funded the research project. Recommendations from this study have a positive impact on the energy efficiency and overall quality of new homes for years to come.

This research study:

  • Took a comprehensive look at various duct materials and component designs
  • Quantified and compared efficiencies
  • Made recommendations for energy efficient duct design
  • Predicted the impact on energy and dollar savings
  • Proved the predicted savings through actual installation and monitoring

There is compelling evidence that galvanized steel duct when properly installed, sealed and insulated provides the most energy efficient and healthy air distribution system available. ADI believes that if reliable data were available, home buyers and homebuilders could make informed choices weighing the cost of a duct system upgrade with the benefits in energy savings and indoor air quality. The overall goal of this research project was to publish reliable efficiency data and design recommendations.

Static Pressure Losses in 6”, 8”, and 10” Non-Metallic Flexible Duct

This study measured airflow static pressure losses through non-metallic flexible ducts in compliance with ASHRAE Standard 120-1999, Methods of Testing to Determine Flow Resistance of HVAC Air Ducts and Fittings (ASHRAE 1999).

A Study of Pressure Losses in Residential Air Distribution Systems

(Indoor Environment Department, Lawrence Berkeley National Laboratory, Bass Abushakra, et al.)
An experimental study was conducted to evaluate the pressure drop characteristics of residential duct system components that are either not available or not thoroughly (sometimes incorrectly) described in existing duct design literature. The tests were designed to imitate cases normally found in typical residential and light commercial installations. (Study Link)

A Comparative Analysis of CFD Delta P versus Measured Delta P for Maximum Stretched, 4%, 15% and 30% Compressed 6” Diameter Flexible Ducts

Fully stretched, 4%, 15% and 30% compressed 6” flexible duct configurations were simulated using CFD software under various volumetric air-flows. CFD simulation results showed close proximity to laboratory experiments for fully-stretched and 30% configurations. This paper to be published in ASHRAE Transactions 1-07.

COMPARATIVE STUDY: CFD Delta P VERSUS MEASURED Delta P FOR 30% FLEXIBLE DUCTS

Non-metallic flexible duct products have achieved wide usage in today’s Heating Ventilating and Air-Conditioning (HVAC) applications, due to their advantages of cost and installation, over metallic ducts. Despite the advantages, an important factor in HVAC duct design is to attain minimum pressure loss throughout the distribution line. Compared to the straight ducts, the compression in flexible ducts results in increased pressure loss thus increased energy consumption.