machine. To determine how much heat has been converted in drying a load of laundry, weigh the clothes when they are wet and then again after the clothes have dried. The difference is the weight of the water that was evaporated from them. Multiply that weight in kg by 2,257 kJ/kg, which is the heat of vaporization per kilogram, to obtain the number of kilojoules that went into evaporating the water, or multiply by 0.6250 kWh/kg to get kilowatt-hours. If the moisture later condenses inside the house, the latent heat will return to ambient heat which could increase the temperature of the air in the room slightly. To obtain a good approximation of the effect this would have in a particular situation, the process can be traced on a psychrometric chart. Factors that determine the drying duration Various factors determine the duration of drying and can help to decide rather to use a drier or a clothes line The environmental temperature - increase of temperature decreases the drying duration The environmental humidity - decrease of humidity will decrease the drying duration Wind velocity - Sometimes people put a fan near the clothes when drying them indoors Direct sun - usually only the external line will be exposed to direct sun, so usually people put the thickest clothes on the most external line. Cloth thickness Drying laundry in freezing conditions Laundry may be dried outdoors when the temperature is well below the freezing point. First, the moisture in the laundry items will freeze and the clothing will become stiff. Then the frost on the clothes will sublimate into the air, leaving the items dry. It takes a long time and it is usually much quicker to dry them indoors, but indoor drying transfers heat from the air to water vapor, so it is a trade-off between speed and energy efficiency. The added humidity cancels out the reduction in air temperature to some extent. North American controversy Controversy surrounding the use of clothes lines has prompted many governments to pass "right-to-dry" laws allowing their use. According to Ian Urbina, a reporter for The New York Times, "the majority of the 60 million people who now live in the country’s [The United States'] roughly 300,000 private communities" are forbidden from using outdoor clothes lines. , the states of Florida, Colorado, Hawaii, Arizona, California, Illinois, Indiana, Louisiana, Maine, Maryland, Massachusetts, Nevada, New Mexico, North