An extensive Computational Fluid Dynamics (CFD) study [pdf] performed over 10 months by a team at Iowa State University [source: green building pro] confirmed what many room occupants long suspected - that fabric ducts offer better indoor air comfort compared to traditional metal ducts. Equally impressive, the study found that the fabric ducts provided a 22-27% improvement in energy efficiency compared to equivalent metal ducts.

Fabric Duct Example

Indoor air comfort includes a measure of how fast and how uniformly a HVAC system can reach a desired temperature. Fabric ducts were known to heat rooms faster and more uniformly than metal ducts but some doubt remained as to their efficiency. The CFD study included transient simulations over a extensive range of conditions. The large energy efficiency gain for fabric ducts over metal ducts was a welcome surprise to some in the fabric duct industry.

It appears that this study confirms a bright future for fabric ducts as part of the quest to improve building energy efficiency, reduce operating costs, and address global warming.