Choosing the Right Fan to Cool Your Home
Using fans to cool your home is energy efficient. After you determine the natural ventilation scheme in your home, you can enhance the effect with the use of active fans. When choosing fans, check for efficiency ratings.
Fans are rated by how much air they can move in a given amount of time. The most common spec is cubic feet per minute (cfm). Calculate how many cubic feet are in your house, room, or attic (length x width x height) to find the proper-size fan.
Fans move air most efficiently when they have a cowling. Cowlings prevent air around the tip of the blades from circling about outside the blades, instead forcing that air forward, yielding much more air for the same power draw.

A cowling on a fan directs airflow and improves efficiency.
Many fans are available at a wide range of prices. Choosing the right unit for your needs can ensure you get the effect you're looking for.
Oscillating fans: These fans move back and forth and work only for convective cooling, and they're dubious at that.
Box fans: Box fans are portable units you can move around as the need occurs. Most have some kind of cowling. Blade design helps determine the efficiency of the air flow.
Window fans: Window fans come with a sheet metal mounting that fits right into an open window and seals around the edges. Most of these fans are very efficient. The best way to move air in your house is by using a good window fan mounted into the most appropriate window, probably upstairs on the downwind side of your house (the fan aims out the window). One small window fan mounted properly can do the same work as a number of large fans scattered about the house.
Exhaust fans: Exhaust fans shouldn't be used when the HVAC system is running, but if you need to, open a small window nearby so that you can control the air movement.
If you're cooking in the summer when the AC is on, exhaust fans can make a big impact on the comfort in your house. This is true especially if you're boiling liquid, because not only does that heat the air, but it also humidifies. Run the fan on high, but crack a nearby window so that you don't pull expensive, cooled air out of your house.
Ceiling fans: Here's how to use your ceiling fan to get the most benefit:
Create convective cooling: With a ceiling fan, you can get convective cooling by running the fan in either direction.

Ceiling fans work best when the fan blades are 7 to 9 feet above the floor and 10 to 12 inches below the ceiling.
Draw the heat up: If you have a vent, you can enhance the chimney effect by running a ceiling fan in the reverse direction (aiming the air flow upward, in other words).
Reverse the chimney effect by pushing hot air down: In the winter, you can use a ceiling fan to push hot air back down into the room.
A well-positioned ceiling fan can allow you to lower your thermostat by 4 degrees Fahrenheit and achieve the same comfort level.
Whole house fans: Whole house fans are mounted in the ceiling between a high point in your house and the attic. They draw air through open windows, exhaust it up through the attic space, and cool the attic space
A great advantage is that you can open any window in the house and get air movement in that room.
Attic vent fans: An attic vent fan draws air in from one part of the attic, and out another. There is no air movement in the house below, so attic vent fans can be run when the house is closed up.

Green Living Glossary
acid rain
A mild acidic solution that falls in rain or as dry particles caused when fossil fuel burning produces sulfur dioxide and nitrogen oxides. Acid rain has been linked to damaging effects on waterways and forests.

Green Living Glossary
active solar design
A strategy for designing high-performance, ultra-energy-efficient buildings. Active solar incorporates all the elements of a passive solar design with additional mechanical equipment, such as pumps or fans, to take advantage of the heat from the sun.

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alternative energy sources
Wind, hydro (water), biomass (fuel from natural material such as crops and agricultural waste), and solar power.

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biodegradable
Made from materials that will decay and break down into naturally occurring elements in a fairly short amount of time.

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biomass
Fuel made from natural material such as crops and agricultural waste.

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Bokashi
A Japanese term referring to a process of fermenting organic matter

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carbon emissions
Carbon released when many substances — particularly fossil fuels such as oil, gas, and coal — are burned by vehicles and planes; by the manufacturing processes of many consumer goods; and by the heating, cooling, and electricity for your home.

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carbon neutral
The state of reducing a person’s carbon emissions as much as possible and balancing the remaining carbon emissions by offsetting them with processes that consume carbon.

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carbon offsets; carbon credits
Paying for or participating in programs that reduce the carbon in the atmosphere. Purchased shares go toward reducing the same amount of environmental costs that an activity expends. Carbon offset programs or projects often involve tree planting because trees have a huge capacity to absorb carbon from the atmosphere. Other programs involve everything from supporting solar and wind power to replacing fossil fuel–burning stoves in developing countries with more sustainable energy sources.

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carcinogen
A cancer-causing substance.

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carpooling
Reducing the number of vehicles going to the same destination by having two or more people ride in the same vehicle. In most cases, carpoolers take turns being the driver and using their own vehicles.

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car-sharing
A system in which a person pays a fee that gives them access to a vehicle (or a pool of vehicles), usually parked in an easily accessible location. Car-sharing can eliminate the need for a personal vehicle.

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climate change; global warming
Changes in the concentrations of various gases in the atmosphere that are affecting the planet’s climate. Many scientists believe that the increase of carbon dioxide is a primary contributor to global warming, which occurs when gases trap warmth in the earth’s atmosphere instead of letting the atmosphere release it.

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compact fluorescent CFL bulbs
Fluorescent light bulbs that fit into a standard light bulb socket and use a fraction of the energy of their incandescent counterparts.

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compost
Decayed plants and other organic matter that breaks down into rich soil.

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core aerating
Poking small holes in the top few inches of lawn to encourage the flow of air, water, and nutrients.

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corporate social responsibility
Principles adopted by a business to make sure that its operations harm no one and instead benefit everyone around it and involved in it.

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daylighting
Bringing natural light into a home.

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ecosystem
A community of living organisms and nonliving materials.

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ecotourism
Sustainable and ethical travel in a natural environment.

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Energy Star
The federal government system for rating energy efficiency in appliances.

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Environmental Protection Agency EPA
Federal agency that regulates environmental laws.

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Fairtrade
System to ensure that workers and producers receive fair value for their products and that mandates sustainable practices in producing those products.

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food miles
The distance food travels from where it’s produced to the consumer.

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foodprint
The amount of land that various diets require to sustain them.

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fossil fuels
The energy-rich organic substances, traced back to the remains of organisms that lived 300 to 400 million years ago, that modern societies burn to provide power.

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geothermal
Energy within the Earth in the form of heat.

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greenhouse effect
The warming of the planet caused by gases in the atmosphere trapping the sun’s heat instead of letting it get through to space. This action is very similar to what happens in a greenhouse.

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greenhouse gases
Gases such as carbon dioxide, methane, and nitrous oxide produced by the burning and processing of fossil fuels and that contribute to global warming and acid rain.

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greywater
Water already used for washing, laundry, or showering that is appropriate for household functions from toilet flushing to watering plants.

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Leadership in Energy and Environmental Design LEED
A scoring system to rate how ecologically friendly buildings are.

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light shelves
White or light-colored horizontal fins above windows that bounce sunlight up onto the ceiling to bring it deeper into the room.

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light-emitting diode LED
A tiny semiconductor that emits light.

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natural gas
An energy source that burns cleaner than coal and oil but still releases carbon dioxide when it burns and methane during production, storage, and transportation.

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organic
Of living things; in food, grown without chemical fertilizers or pesticides or genetically modified organisms.

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passive solar design
Building design that takes advantage of the fact that the summer sun is higher than the winter sun. Overhangs shade the building from the summer sun and allow the lower winter sun to enter the building and heat it.

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petrochemicals
Chemicals derived from petroleum.

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phantom load; standby power
Energy drawn by a plugged-in appliance even when the appliance is turned off.

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plastic identification code
A triangle with a number from 1 to 7 inside indicating what type of plastic an item is made from.

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PV cell
A photovoltaic cell; a cell with a thin semiconductor that converts solar power into electricity.

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recycling
Collecting goods that have reached the end of their lives and processing them, their parts, or some of their parts, into the raw materials from which new goods are made.

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renewable energy
Energy from sources that cannot be used up, such as wind, water, and the sun.

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skylight
A rooftop window that brings in twice the light of a traditional window of the same size.

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solar panel
A panel containing cells that convert sunlight into electricity.

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sun tunnel
A passage that brings light into a room by bouncing sunlight through a small dome skylight on the roof connected to another skylight on the ceiling of the room. (Also known as a sun tube, sun pipe, and solar tube.)

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sustainable
Using natural resources in a way that allows for continued viability.

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thermal hole
An opening such as a window that leaks heat and air-conditioning energy.

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thermal mass
The ability of a material to absorb and store temperature.

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three Rs
The environmental practices of reducing consumption, reusing items, and recycling.

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top-dressing
Applying a light scattering of compost, other mulch, or sometimes fertilizer, over soil surfaces to add organic matter or nutrients without digging it in

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toxic waste
Disposed materials that can cause harm to people, animals, or the environment.

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vermicomposting
Composting with worms.

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xeriscaping
Landscaping for water conservation; a practice of garden planning and maintenance.