Two types of flex transition hose to connect the dryer to the wall outlet. This video discusses the pros and cons of each and demonstrates tricks or tips to best secure the flex hose. Safe Dryer Venting. Protect your home from a dryer fire. Make your laundry room feel bigger.
New for 2012 is this pretty impressive DryerFlex product. See it at www.dryerflex.com
My lengthy reply to the comment from mid 2012.
The connection between the dryer and the wall outlet in the majority of cases, if not 90% of them, requires some sort of expandable and flexible hose, so that a person can make the positive connection to each outlet. In cases where the dryer can be located far enough away from the wall to allow access to make those two positive connections with hard pipe, then I agree, rigid or hard pipe is the best.
A point you hinted around was that screws and tape should be used at each joint or connection. Both the International Building Code and the Uniform Building Code explicitly point out that any sort of penetration (screw) is forbidden. The most popular and dependable mechanism to tighten the flex hose around the rigid pipe is the worm drive hose clamp.
The wire bound foil flex is very easy to work with and has impressive stretch to compressed ratio but since the foil material collapses or folds within the opening, the 4 inch space shrinks to a very abrasive 3 ¼" opening, increasing the airflow friction and therefore a poor choice when considering efficiency.
The aluminum flex or semi rigid flex, which is often specified in the dryer manufacturers' installation manual due to its fire retardant capabilities is much more difficult to work with, exhibits very poor stretch to compression ratio and just meets the testing standards set forth in the International Building Code dealing with its puncture and deforming characteristics. The value in using this flex is that the inside dimension of 4" is never compromised and the smooth interior surfaces provide little friction and therefore a smart efficiency choice.
What I have discovered is a brand new and very impressive hybrid flex that combines the ease of use and flexibility of the wire-bound foil flex with the fire resistance and airflow efficiency of semi-rigid aluminum flex. And this is the only flexible duct on the market that has a zero flame spread and zero smoke development rating and that meets the International Residential & Mechanical Codes M1502 and 504 to be specific which require meeting the UL2158A standard.
Let's revisit the deformation and puncture issues that the code references. When I applied equal pressure to the three types of flex, I noted how well the DryerFlex recovered from the effort to deform it. The aluminum flex easily deformed and did not rebound.
For whatever it is worth, there are hundreds of national and independent duct cleaning firms that have switched 100% to the DryerFlex product. Yeah, hard to believe, but once you hold this new Dryer-Flex in your own hand you'll see why. In my honest opinion it is the safest, most efficient and easiest to work with clothes dryer transition duct on the market. I did my own fire test, and it is installed in my house. Thanks again for the comment.