The dryer vent information on this site is outdated. Most of the information is wrong from thickness of solid metal pipe which now has to be 28 gauge galv or better to the fact that dryer vent sections are now required to be mechanically fastened in three places by screws or rivets to prevent separation during cleaning or fires. Should update it to follow 2012 IRC requirements.
Not sure where you got your information.
The dryer vent information is NOT outdated at “this” InterNachi website page.
From Inspecting the Dryer Exhaust - InterNACHI http://www.nachi.org/inspecting-dryer-exhaust.htm#ixzz2v2HD27ed
“According to the requirements of the 2009 International Residential Code (IRC) M1502, the clothes dryer exhaust duct should be made of metal, with No. 28-gauge thickness”
Maybe you should call 911
Article on internachi site: Dryer Vent Safety
“Exhaust ducts shall not be connected with sheet-metal screws or fastening means which extend into the duct.”
Refers to 2009 IRC. 2012 IRC requires duct to be mechanically fastened at the joints