Avoid Sharp Bends: When bends are necessary, use less than 90-degree bends. Be sure to keep 90-degree bends to a minimum. Every 90-degree bend is the equivalent of ten feet of vent run. Never install a dryer vent which has a bend greater than 90 degrees.
In summary, while flexible accordion piping may seem like a convenient option for dryer venting, a hard pipe provides better airflow, fire safety, durability, and aesthetics. Investing in a hard pipe may cost a bit more upfront, but the long-term benefits make it a worthwhile investment for any homeowner.
Keep exhaust duct as straight and short as possible. Exhaust systems longer than the manufacturer's recommendations can extend drying times, affect appliance operation and may encourage lint build-up on pipe lining.
Look for a rigid metal (aluminum or galvanized steel) exhaust duct connecting the transition duct to the exhaust duct outlet terminal. 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).
The vent hose can become crushed or kinked, especially if the dryer is pushed too close to the wall. This restricts airflow and forces the dryer to work harder, which can cause overheating and increased wear and tear on the appliance.
M1502.
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 maximum length of the exhaust duct does not include the transition duct. This means that vents should also be as straight as possible and cannot be longer than 35 feet.
Avoid Sharp Bends: When bends are necessary, use less than 90-degree bends. Be sure to keep 90-degree bends to a minimum. Every 90-degree bend is the equivalent of ten feet of vent run. Never install a dryer vent which has a bend greater than 90 degrees.
Per the requirements of the International Residential Code, Section M1502 (2009-2021 IRC), the clothes dryer exhaust duct should be a rigid or semi-rigid metal duct made of galvanized steel or galvanized aluminum with a smooth interior finish and a duct diameter of 4 inches.
Close vent offsets between dryer and wall vent located on same wall as dryer (Offsets between 6-9 inches): The MV-90 can be coupled directly to a standard 4 inch diameter, adjustable, 90 degree elbow which creates a 9 inch offset.
The effective length of a dryer duct with bends increases by 2.5 feet for each 45 turn and 5 feet for each 90-degree curving. If a clothes dryer vent is 25 feet long and has three 90 elbows, which is very common, it would have an equivalent measure of 25 + (3×5) = 40 feet!
M1502.
According to the 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.
The most common place to vent your dryer is horizontally through the exterior wall near the dryer, which is the ideal placement. Other common locations are through (but not into) the basement or the attic/roof. For most dryer models, you can't run the exhaust duct more than 25 feet from the dryer to the exhaust port.
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.
These self-supporting semi-rigid ducts can be bent into place and yet still stay in place for heavy-duty applications.
A short-90 degree is fine on a vent, but not allowed on a drain - as there's not much to get 'stuck' in a vent. Typically a 90 would be used on a vent as its fewer connections and less work, but no issue if you want to use two 45s.
Depending on the location of your vent, you may require an elbow to connect to the vent hood duct. You may have two elbows back-to-back to get the run to line up the path from the dryer. Install a duct elbow onto the dryer, if necessary.
Yes, that's considered safe. The operating temperature of a dryer vent is not a problem for direct wood contact. Keep the vent clear and you'll have no fire. Ensure all joints are foil taped, so lint does not escape from the pipe.
Of all of the dryer duct materials, rigid metal ducts catch the least amount of lint. Rigid metal ducts are more expensive than other types, but they are durable and efficient. Building codes generally allow for runs as long as 35 feet, compared to the 8-foot maximum for flexible transition tubing.
You need to have the shortest run possible to the exterior. You definitely do not want a dryer exhaust line to slope upwards (not even straight pipe) because the weight of the column of air as well as the lint accumulation would really cut down the flow rate.
PVC is plastic and not conducive for dryer vents. When lint travels through a PVC pipe, static electricity created by the plastic will pull the lint to the sides. Over times this causes a 4” pipe opening to shrink dramatically. This leads to poor airflow which creates drying exhaust issues.
DO NOT terminate dryer vents in crawl spaces or attics. Dryer vents that terminate in crawl spaces or attics allow for moisture to deposit and encourage mold growth and health hazards. Dryer vents must terminate outside of the building.
There are variables that affects how often you should clean your dryer vent system. Generally speaking, the clothes dryer itself, as well as the vent should be cleaned every 1 to 3 years.