UPDATED on 7/7/2016 with information on heat pump clothes dryers from Whirlpool and LG.
In an American home with a relatively new refrigerator, the clothes dryer usually uses more energy than any other home appliance. An electric clothes dryer draws between 4,000 and 6,000 watts, and costs about 60 cents an hour — about $158 per year, on average — to operate. While a gas dryer may only draw 400 watts of electricity, it also consumes a significant amount of natural gas or propane to dry each load of laundry.
Besides using lots of energy, clothes dryers can also contribute to depressurization and backdrafting problems. The typical American clothes dryer is vented to the exterior; when operating, a dryer depressurizes a house at a rate of 100 to 225 cfm. This depressurization, especially when combined with other exhaust appliances operating simultaneously, can cause gas water heaters or wood stoves to backdraft. Even when the dryer isn’t operating, a dryer vent represents a penetration in the thermal envelope that contributes to air leakage.
Finally, clothes dryer vents are a major cause of house fires, so a house without a dryer vent is a safer house. For all of these reasons, you may be thinking of living without a clothes dryer.
Do washing machines have effective spin cycles?
Newer washing machines do a better job of spinning clothes to remove moisture than older models. Still, some people claim that a better spin cycle would reduce drying time. One possible solution is a new appliance called a spin dryer.
Of course, moving clothes from the washer to the spin dryer, and then moving the clothes again from the spin dryer to a clothesline or conventional dryer, is a hassle. Moreover, these spin dryers have mixed reviews; according to some users, they don’t really reduce drying time significantly.
Clotheslines and indoor drying racks
The most obvious alternative to a clothes dryer is a traditional outdoor clothesline, supplemented by an indoor wooden drying rack.
Outdoor clotheslines are a badge of honor among environmentalists; my 83-year-old mother still dries all her clothes that way. Unfortunately, some homeowners’ associations and local ordinances restrict the use of outdoor clotheslines. A variety of citizens’ groups operating under the “Right to Dry” banner are challenging these ridiculous restrictions; for more information on their efforts, check out the Project Laundry List Web site.
Condensing clothes dryers
Condensing clothes dryers don’t require a vent; instead of blowing the moisture outdoors, these appliances collect the moisture condensed during the drying cycle and send it down the drain.
Several manufacturers make condensing dryers, including Bosch, Equator Appliances, and LG. Some are stand-alone dryers, while others are washer-dryer combos with a single drum. These appliances include an electric-resistance heating element, just like a conventional clothes dryer. Unlike most dryers, however, they use cold water from the home’s domestic water supply to provide a condensing surface that encourages condensation. Some models blow the warm, humid air inside the dryer across a copper coil circulating cold tap water, while others have a condensation chamber where the humid air contacts a cold-water spray.
Condensing dryers require a cold-water connection and a drain connection. Here’s how the clothes drying cycle for the EZ 3720 CEE washer/dryer combo from Equator Appliances works: the dryer has a 120-volt electric heating element; the circulating warm air blowing through the damp clothes is brought in contact with a sheet-metal baffle that is cooled by a continuous spray of cold water. Some of the moisture in the warm, humid air stream condenses in mid air, and more moisture condenses on the cold metal baffle. All of the water — both the water sprayed on the baffle and the collected condensation — drips to a sump at the bottom of the appliance, where it is removed by a pump, just like the drain water removed from a washing machine. A normal drying cycle requires 2 hours per laundry load.
The main advantage of condensing dryers is that they don’t require a vent through the wall. However, they have at least two disadvantages:
- They are slower than conventional dryers, and
- According to one source, they use more energy than a conventional dryer.
Heat-pump clothes dryers
Heat-pump clothes dryers work like condensing clothes dryers, except they use an air-source heat pump instead of an electric resistance element to raise the temperature of the air inside the dryer.
Like a stand-alone dehumidifier, a heat-pump clothes dryer is a closed system, entirely within the home’s conditioned envelope. Both sides of the heat pump — both the condenser coil and the evaporator coil — are located inside the appliance. Most heat-pump clothes dryers are unvented; like condensing clothes dryers, they collect condensed moisture and send it down the drain.
Several European appliance manufacturers sell heat-pump clothes dryers; one of the first models to hit the market was the Ã–ko-Lavatherm WP dryer from AEG, which you can read about here. Another heat-pump clothes dryer sold in Europe is the Bosch EcoLogixx 7 dryer.
Whirlpool and LG now sell heat-pump clothes dryers in the U.S. To learn more about these clothes dryers, see these two articles:
Heat-pump clothes dryers use significantly less energy than conventional electric dryers. The major downside to heat-pump clothes dryers is their high cost — about twice the cost of a conventional electric clothes dryer — and their mechanical complexity.
Drying cabinets, drying closets, and drying rooms
In many European homes, especially Passivhaus homes, clothes are dried indoors in a drying cabinet, drying closet, or drying room. Drying is accelerated with help from a dehumidifier, mechanical ventilation, or a combination of mechanical ventilation and added heat.
A homemade drying cabinet would consist of a large cabinet with horizontal closet rods or dowels. The cabinet should have an air intake at the bottom and a connection to a low-cfm exhaust fan or the exhaust side of an HRV at the top. The inclusion of an electric resistance heating element (the Staber model includes a 1,200-watt heating element) is optional, as is a floor drain. Of course, unheated drying cabinets take longer (but use significantly less energy) to dry clothes than heated drying cabinets.
If a drying cabinet is too small for your needs, you could expand the concept and build a drying closet. In a post on one of GBA’s Q&A pages, Lucas Durand suggested locating a home’s water heater in a clothes-drying closet, so that the waste heat from the water heater helps dry damp clothes.
Instead of an electric resistance heating element, some drying cabinets or drying closets use a dehumidifier. For more information on drying closets with dehumidifiers, see this British Web page.
In a co-housing or multifamily building, a drying closet can be expanded into a drying room. Drying rooms are very common at cross-country ski lodges and in the basement laundry rooms of some European apartment buildings; these rooms typically include exhaust ventilation and a heat source. I’ve been told that the drying rooms in many Swiss apartment buildings and homes use a dehumidifier / fan product called Secomat that has been designed by the manufacturer (Krueger) specifically for clothes-drying rooms.
Last week’s blog: “Can ‘Passive House’ Be Trademarked?”