Outdoor clotheslines will save you money and your home from mold and unhealthy chemical pollution.

Line-drying your clothes is one of the easiest ways to reduce your energy usage, save a little cash, and keep a few pounds of carbon dioxide out of the atmosphere.

It's also the fastest way to pollute your home if done indoors, finds a new report from Scotland. Engineers and public health researchers from the Mackintosh Environmental Architecture Research Unit at Glasgow School of Art conducted a three-year study on public housing units, and found that the practice of drying laundry indoors to save energy was causing health problems and, in some cases, was actually leading to an increase in home energy use. 

The average home has between five and 10 liters of water (roughly 1.0 to 2.5 gallons) in the air at any given time. But a load of laundry can release 2 liters (about 0.5 gallon) into the air, accounting for more than a third of the humidity in your home on laundry day. And here's what that can leave behind.

Higher chemical pollution: People who use fabric softeners are likely to have higher levels of cancer-causing chemicals called acetaldehydes in their indoor air. Other chemicals used in laundry detergents can off-gas into the air, and the levels go up with the amount of moisture in the air.

Greater mold potential: Mold spores were 300 percent higher than what's considered safe when laundry was dried indoors. In 25 percent of the homes surveyed, the authors found high levels of a mold spore called Aspergillus fumigatus, which is known to cause lung infections in people with weakened immune systems.

More dust mites: Humid homes are ripe for dust-mite growth, and dust mites can cause allergies and asthma attacks.

Higher energy bills: One interesting finding of the report was that in about 23 to 37 percent of the homes surveyed, tenants would raise the heat or open a window to speed drying of laundry, which negated any energy savings of not using their dryers.

So how can you avoid all of the above and still not run up your electricity bill?

• Get an outdoor clothesline. This is the easiest fix, and one that's totally doable if you have a backyard or an apartment or condo with a balcony. Need some tips on setting one up? Here's our Clothesline 101.

• Upgrade your washer and dryer. Dryers are inherently energy-intensive, and all models use about the same amount of energy, according to the Environmental Protection Agency's EnergyStar program. But if yours is in need of an upgrade, look for a model with a moisture sensor, which automatically shuts the dryer off when your clothes are dry. Also, upgrade your washer to one with faster spin cycles, ideally up to 1800 rpm's. A fast spin wrings the most water out of your clothes, so your dryer needs less energy to dry them. 

• Clean out your lint filter. Regardless of how old your dryer is, clearing the filter will reduce the amount of energy the machine uses.

• Dry loads of similar fabrics. Different fabrics take different amounts of time to dry, and "over-drying" some clothes while others finish drying wastes energy and is hard on your clothing.