ASHRAE Research on Roof-Mounted Equipment, Phenolic Ducts Completed

Completed Research, March 2019

1692

ASHRAE has teamed with the Insurance Institute for Business and Home Safety (IBHS) to study the effect architectural screens have on wind loads to roof-mounted equipment (RME). The use of these screens is common and even required in some instances, but codes do not allow for reduction of wind loads to RME when used.

An ASHRAE research project looked at how to calculate wind loads on these porous structures and how to calculate the load impact of these screens on wind loads to RME, so that codes may be able to accurately consider their use. This project looked at factors to quantify the shielding effects of screen walls including net free area and aspect ratio of screen openings, location, configuration and elevation ratios of screen walls and RME on roofs.

The final report details the results and key findings. A technical paper has been submitted for future publication in ASHRAE’s Science and Technology for the Built Environment.

1692-URP, Effects of Shielding on the Wind Loads on Roof Mounted Equipment, was sponsored by TC 2.7, Seismic, Wind and Flood Resistant Design. The principal investigator was Dr. Murray Morrison with the IBHS.  

1764

Phenolic ducts are relatively new to the North American market. Typical phenolic ducts consist of a fiber-free rigid thermoset phenolic insulation core faced with embossed or smooth aluminum foil on the interior and exterior of the duct.  

To ensure designers can properly design these duct systems, an ASHRAE research project measured the relative and absolute roughness of phenolic duct systems (connected with a four-bolt flange and cleat joint) for seven distinct rectangular cross sections. The study found the flanges are the dominant effect on relative roughness and that the ducts tested have about 1.5 to 2.8 times more absolute roughness than the average value for galvanized steel ducts in the ASHRAE Handbook.  

Full results from this project can be included in the ASHRAE Duct Fitting Database and the ASHRAE Handbook. A technical paper has been submitted for future publication in ASHRAE’s Science and Technology for the Built Environment.

1764-RP, Determine the Absolute Roughness for Phenolic Duct, was sponsored by TC 5.2, Duct Design. The principal investigator was Dr. Stephen Idem with Tennessee Technological University.   

The final reports for these projects are available for free to ASHRAE members at www.ashrae.org/technical-resources/technology-portal. ASHRAE Transactions papers are available for $5 to ASHRAE members at www.ashrae.org/bookstore.