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Close your blinds/curtains. Turn off all unnecessary heat-producing devices, appliances, and lights. Pick up the clutter. Open a window and close off other rooms in the house.
About 30 percent of unwanted heat comes from windows. Close your window coverings to prevent direct sunlight from heating up the room. If you don't already have blinds or curtains in the room, invest in some, especially if you have any south or west-facing windows. By using window coverings, you can reduce indoor temperatures by up to 20 degrees. Try to keep the window coverings closed from morning until late afternoon when the sun is at its peak. If heat is a persistent problem in the room, consider purchasing thermal insulated blackout curtains. Any device that is powered on is currently contributing to the heat in the room. Unplug or turn off everything you're not using. Computers and televisions, in particular, generate a lot of heat. Incandescent lightbulbs are big heat-generators, too. If possible, turn the lights off in the room. It's not always feasible to turn out all the lights. At the very least, dim them as much as you can. Consider replacing your incandescent lights with compact fluorescent lamps, or better yet, light-emitting diodes which generate far less heat. CFLs and LEDs are more environmentally-friendly, as well. Piles of clothing and other kinds of clutter absorb heat and keep it trapped in the room. The less clutter you have in the room, the more available space there is for the heat to disperse and the faster it will cool down. A lot of clutter can also restrict airflow, making it feel even hotter in the room. Toss any piles of clothing you have on the floor into your closet and shut the door behind them. Do a quick survey of the remaining clutter and quickly eliminate what you can. If it's hotter inside the room than it is outside, the walls have probably absorbed a lot of heat from sunlight throughout the day. Remove this trapped heat and push it outdoors by opening the windows in the room. Close off any spaces in the house that you currently aren't using, too. This will help to cool down the room you're in more quickly. Once it cools off a bit, be sure to close the windows.