Roof Dryer Venting Guide | DryerJack

Roof Dryer Venting Guide

  • 4" minimum diameter is the requirement for dryer ducting. To encourage air flow efficiency, the ducts must be clean, frictionless and unobstructed. This adds to your clothing's lifespan and cuts down on utility costs. By installing the DryerFlex, you meet the 4" diameter specs.
  • Between the dryer and the wall outlet, the flexible transition hose should be the foil type or the aluminum flexible duct, which is preferred most. No plastic or vinyl.
  • Any concealed ductwork must be galvanized or aluminum rigid metal duct.
  • Any joints in the ducts shall be installed so the direction of air flow is pointing in the same direction as the male end of the duct points.
  • Metal tape, NOT duct tape, should secure any joints. Any rivets or screws in the duct track will encourage lint collections.
  • Concealed rigid metal ducting length should not exceed 35 feet or 25 feet for IRC. Every 90 degree elbow takes off 5 feet from this run. Every 45 degree fitting removes 2.5 feet from this limit. (the Dryer-Ell is an exception under 2006 IRC Section M1502.6, 2009 IMC Section 504.6.4 and 2009 IRC Section M1502.4). Check the local codes and dryer manufacturers recommendations for specifics in your area.
  • Dryer venting cannot be combined with other systems, such as chimneys or exhaust vents.
  • A proper hood or a roof cap equipped with a backdraft damper must be at the termination of dryer venting. Metal screen with small orifice openings should not block the hood or roof cap, as this blocks the opening by catching lint. This happens quickly. The opening of the hood should point down and have 12 inches clearance between bottom of hood and any obstructions, including the ground.
  • Attaching Aluminum Flex tip: Using a pipe like a dough roller, flatten aluminum flex. Click here for an image. And a video here.
  • The model 425 and 350 port openings comparison graphic here
  • We have some very important tips for proper Dryerbox installation and avoiding pitfalls troublehooter here..
  • Dryer venting should always be installed properly for safety reasons.
  • Every day, there are dryer fires in the news. Click here to see the importance of proper venting.

Good Practices

  • It's always a good idea to inspect the termination port of the dryer duct along with the wall or roof cap. Birds tend to build their nests in these and they may become clogged by other means. Check for the proper exit velocity of the air escaping the vent and try to look and feel the interior walls of the duct.
  • Suspected clogging or partially clogged ducting exhaust likely means you will need to hire a duct cleaner. This dryer duct cleaning helps to improve the safety and efficiency. You should have the ducts cleaned and inspected every six to twelve months.
  • Kinked or crushed hose is also a safety hazard. Allow adequate room behind the dryer for the flex transition hose to make its bends with minimal restrictions or deflections.
  • Sometimes labeled as "Routine and Problem Cleaning", dryer vent cleaning is a professional service.
  • A "jet-snake" is used during routine cleaning from the outside. It sends a blast of air backwards, knocking the lint loose and blowing it outside and is caught in a special bag.
  • When a dryer is not drying clothes fast enough, a "Problem Cleaning" is performed. This consists of disconnecting, pulling the dryer out, installing a large blower on the vent, then blowing, brushing, vacuuming and/or dismantling the ductwork to make sure it is properly cleaned.
  • Find a duct cleaning service or search for duct cleaners in your area online. Use our locator here
  • Mostly prohibited by appliance manufacturers and building departments, using white vinyl flex pipe has been shown to be a dangerous add-on. Almost all appliance manufacturers require the use of aluminum flexible pipe, even if some municipalities allow or don't discourage the foil-covered vinyl flex. A useful comparison is located here.
  • Exhaust duct should be kept as short and as straight as possible. Longer exhaust systems than is recommended by the manufacturers can affect the appliance's operation, make drying times longer and may produce more build-up on the lining of the pipe.
  • You can find more information about dryer vent cleaning at . This site provides excellent information about vent maintenance, cleaning and solutions.
  • Overdrying your laundry is not only wasteful, energy-wise, but is also damaging to your laundry. Use automatic settings on your dryer, when available, such as "less dry" rather than a timed setting.
  • Lint filters needs to be cleaned every time you finish a load of laundry. This habit will improve the performance of the machine, extend the life of the appliance, save energy and minimize fire hazards.