A rigid metal duct tends to be the best type of dryer vent hose. This tube provides a straight, direct line to the outside. Its inner wall is smooth, and it lacks the ribs found in flexible dryer hoses.
Dryer vents should either be solid steel vent pipe or solid aluminum vent pipe. Do not use plastic vent pipe! its a safety and fire hazard. Aluminum foil vent pipes are almost as bad as plastic but still safer being less of a fire hazard...
Ideally you want rigid metal duct. Having less change of crimping and bending means less chance of lint buildup, which means less chance of fire hazard.
The metal duct is much safer than the foil duct. Using the rigid duct is the most efficient, as far as airflow, and running as straight a path as possible will improve efficiency (as well as collect less lint and be easier to clean). The semi-rigid duct is almost as good--much better than what you have on there now.
Vent Type and Length
Any Dryer ducting used must be UL-listed. UL now requires that all Dryers be installed with either rigid or flexible metal ducting. Rigid is preferred. A UL-listed semi-rigid Dryer duct can be used if the vent length is 8 feet or less.
M1502.
The maximum developed length of a clothes dryer exhaust duct shall not exceed 35 feet from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet for each 45-degree (0.8 rad) bend, and 5 feet for each 90-degree (1.6 rad) bend.
The exhaust duct should be rigid metal 4 inches in diameter and no more than 35 feet in length or as specified by the duct manufacturer. This length should be decreased by 2.5 feet for every 45-degree bend the duct makes and 5 feet for every 90-degree bend the duct makes.
Like vinyl ducts, these ducts impede airflow and trap lint. Aluminum foil won't burn, of course, but it will quickly disintegrate in a fire. Dryer manufacturers don't recommend foil ducts and neither do we.
The most durable type of exterior wall vent cover is the type made of metal with a magnetic door or damper that remains closed when the dryer is not in use.
Disadvantages of Flex Duct
Flexible ducts are more prone to air leakage around the seams, which can lead to lower HVAC system performance. Additionally, the pliable nature of flex duct tends to make them prone to tangling or crushing when they pass through tight spaces or fixtures.
The ridges and creases in flexible piping can trap lint and other debris, which can quickly accumulate and become a fire hazard. A hard pipe, on the other hand, is smooth and provides no places for debris to gather.
Rigid ducts are made from galvanized steel or aluminum. They can be either rectangular or cylindrical in shape. Rigid ducts are more durable than flexible ducts and can withstand extreme temperatures.
Semi-rigid is accepted under standard building code because it maintains its 4" diameter and has a smooth interior. It is harder to work with, crushes easily and is difficult to twist. DryerFlex is also code approved with a UL 2158A listing, but it is very workable making it easier to connect the dryer.
Route the dryer vent horizontally to the home's outside wall. Duct work should pitch 1/4-inch per foot to the outside. This keeps moisture out of the pipe. For basement laundry areas where your ductwork will run vertically to the outside wall, you may need to use 90-degree elbows.
A good technique is to restrict the dryer exhaust duct from passing through an attached garage. Ducts in the garage or penetrating the walls or ceilings separating the dwelling from the garage must be constructed of minimum No. 26-gauge sheet steel or other approved material, having no openings into the garage.
According to most building codes, dryer vents don't need insulation. But, it can be a good idea—especially if your laundry is located in or runs through an unheated area of your home, like a basement or crawl space.
Rigid Metal Ducting: Rigid metal ducting, such as aluminum or galvanized steel, is widely considered the gold standard for dryer vent systems. These materials are non-combustible and can withstand high temperatures, reducing the risk of fires.
Venting a dryer through the roof is possible, but there are important considerations to remember. This method can be practical when sidewall venting isn't an option due to your building's layout. However, overall, sidewall venting is considered the safer option.
A rigid metal duct tends to be the best type of dryer vent hose. This tube provides a straight, direct line to the outside. Its inner wall is smooth, and it lacks the ribs found in flexible dryer hoses.
M1502.
5 code, the construction of a dryer duct has to be a minimum of 0.4 mm thick with a smooth interior. This means ribbed vents are no longer being used. Additionally, all duct joints must point in the direction of airflow.
Dryer venting tips and practices
Flexible transition hose between the dryer and the wall outlet should be either the foil type or the aluminum flexible duct (most preferred). Do not use the plastic or vinyl. Concealed ducting must be rigid metal (galvanized or aluminum) duct.
The dryer needs to be installed near an external vent that has been fitted into an external wall, allowing the damp air to escape outside. Thanks to the external vent, there is no need to worry about empting water from the machine.
The dryer vent is connected to a tube, mostly made of aluminum which is fed to the outdoors and is known as dryer hose. Old vinyl and plastic were also used for making of the dryer hose, but are discontinued because of fire hazards and other safety purposes. This dryer hose is commonly known as the dryer vent.