Condensing dryers are a type of clothes dryers that do not require an external exhaust vent. Traditional dryers tumble clothes in heated air, and as the moisture evaporates from the clothing, the air is discharged through a duct into a vent to the outside. Vents can be difficult to place in apartments and other buildings where the laundry area is not located on an exterior wall. Condensing dryers are also known as ventless dryers, because they do not require ductwork for vented exhaust.
Instead of venting the exhaust air to the outside, a ventless dryer works by cooling the heated air to condense the moisture that is present into liquid form. There are different types of condensing dryers, including units that use a heat exchanger to cool the air, units that draw in cooler outside air to cool the heated dryer air and units that feature a water cooling system. Depending on the design of the dryer, the resulting condensation will either flow into a drainpipe or will be collected in a container that must be periodically emptied. There are combination washer/dryer designs, in which the same appliance is both a washing machine and a ventless dryer.
Keeping a ventless dryer running properly and efficiently does require periodic maintenance. As with traditional dryers, condensing dryers have lint filters that need to be cleaned between each use. If the dryer collects condensation in a separate container, the container will need to be emptied by hand. The condenser unit itself also needs to be cleaned periodically to remove lint and debris and to prevent them from clogging the unit. Condensing dryers do not have ductwork or exterior vents that would require periodic cleaning, and they can eliminate moisture problems that are sometimes associated with long lengths of complicated ductwork.
Unlike washing machines, energy ratings are not typically published for clothes dryers. Condensing dryers were originally designed to eliminate the need for an exterior vent and not specifically for increased energy efficiency. There are models with newer technologies that are more energy efficient than standard dryers. Models that automatically sense when the clothes are dry are more energy efficient and help to conserve electricity.
Condensing dryers do tend to be slightly more expensive than conventional dryers, and they typically take a longer time to dry the same amount of clothing. Combination washer/dryer appliances cost less than buying two stand-alone appliances, and they require less space. Stand-alone dryers typically have a higher load capacity than combination units. Air-cooled ventless dryers will raise the surrounding room temperature and are not as practical in hot climates. Water-cooled dryers increase water usage and are not as practical in areas where there is a water shortage.