Sheet Metal & Air Conditioning Contractors’ National Association


SMACNA’s HVAC Duct Construction Standards, 4th edition, ready for public review

Oct 10, 2017

HVACThe fourth edition of SMACNA’s flagship “HVAC Duct Construction Standards-Metal & Flexible” is now available for 45-day public review.

Continuing to build on the history of the duct construction standards, this new edition represents the state-of-the-art in sheet metal duct fabrication and installation. Comments must be received by Nov. 9, 2017 at 5 p.m. (EST).

Significant changes from the third edition include:

  • Tables for spiral flat oval duct for positive and negative pressure applications
  • Options for internal supports for flat oval duct
  • Information on spray and aerosolized duct sealants
  • Updated liner requirements to include non-fiberglass liner types
  • Added information for lined round duct
  • Added details for hangers to better illustrate where hangers are required
  • Updated requirements for flex duct hanger spacing and hanger width
  • Additional information for spiral fittings.

To provide input, visit the Papers and Guidelines section on SMACNA’s Technical Resources webpage,