Evaporative Coolers & Home Ventilation
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A customer recently contacted our service department with a common complaint. Her portable evaporative cooler wasn't working. She'd placed it in her home office and it hadn't lower the temperature at all. It was 77°F when she turned it on and it was still 77°F two hours later. The only thing that had changed was the humidity. It had risen from 29 to 50 percent. Needless to say, she was upset, but the problem was her cooler, it was her office. It was completely sealed, with no ventilation points besides an air conditioning vent in the ceiling. It was the perfect place for an air conditioner, but not an evaporative cooler. Evaporative coolers require home ventilation. They don't work in closed environments. If you want to enjoy the savings and comfort they provide, you need to make sure they're placed somewhere with steady stream of fresh air. For our customer, this meant opening a window. Once the air could get in and the humidyt could escape, the evaporative cooling mechanism was finally able to operate and it brought the temperature down in no time.
Why Evaporative Coolers Require Home Ventilation
Evaporative cooling is governed by three factors. The first is temperature, which determines the amount of energy water molecules have. The more energy, the more likely they are to break the bonds between them and become water vapor. The second is humidity. When humidity is low, evaporation happens quickly and when it's high, it happens slowly. The more water vapor is in the air already, the less vapor the air can absorb. The final factor is air flow. Evaporation raises the humidity level along its surface. By replacing humid air with dry air, air flow speeds evaporation lowers humidity levels along the water's surface.
In a ventilated room, these factors all work together in an evaporative cooler. When the wind from the fan hits the cooling pad, the heat causes the water to evaporate. Evaporation absorbs a lot of heat, so the air coming out of the cooler is a lot colder than the air going in. The fan speed makes sure evaporation happens quickly and as long as humidity is low, everything runs smoothly. In a sealed room, however, humidity won't stay low for long. As water evaporates, it raises the humidity level until eventaully the air being pulled into the cooler is just as humid as the air being pushed out and evaporation stops. The only way to prevent this is to create an airflow cycle that will push the old air out and bring fresh air in.
How to Ventilate Your Home
Home ventilation requires clear pathways for air to enter and exit your home as smoothly as possible using negative air pressure, whcih occurs when the air density inside a room is less than the density of the air outside. This creates a pressure differential that draws in air from the surrounding area. If venting is constant, airflow will be continual.
Windows and Doors
The easiest way to ventilate your home is to create a cross breeze by opening your doors and windows. Ventilation occurs as long as at least two windows or doors are open, but because air flows faster in straight lines than it does at right angles, air flow is best when the openings are directly across from one another. Portable evaporative coolers actually accelerate air flow by making sure the air is moving constantly. They work best if they're place in front of one opening at another one directly opposite. This not only gives ensures access to a steady stream of fresh air, but the cool air coming out will help push the humid air out the window and pull more air in. Another way to accelerate airflow is to open one set of windows completely, but open the other set only partially. This allows air to escape faster than it can be drawn in, increasing negative room pressure.
If you have a multi-story home, you can ventilate the upstairs and downstairs using the chimney effect. Because hot air rises, heat nautally accumulates in the top levels of your home. If you open the upstairs windows on one side of your house and open the downstairs windows on the other side, your house will If you open the upstairs windows and place your evaporative cooler in front of an opening downstairs, you'll force the hot air out through the upper windows and draw in fresh air through the lowr windows. If you set up your portable evaporative cooler downstairs, the cool air it generates will get pulled up upstairs and cool your entire house. In order to maximize airflow, make sure you only open doors to rooms you want to cool.
Home Improvements
In addition to leaving your doors and windows open, there are also some home improvements you can make to improve air circulation in your home. They provide more outside openings, help you control airflow, and improve air circulation in your home.
| Feature | How It Works |
| Transom Windows | Narrow, horizontal windows that fit above your door. Can be opened to allow air circulation. Their small size helps establish negative room pressure |
| Air Louvers | Angled window shutters that can be adjusted to customize airflow. |
| Undercut Doors | Doors whose bottom edge has greater than normal clearance. Allows air flow into closed rooms. |
Certain features may work better in certain areas of your house than others. Talk to a contractor to see how and where they can help you.
Fans
Ceiling fans, floor fans, and table fans are a great way to spur air circulation, especially in large spaces. For maximum circulation, position ceiling fans 7-9 feet from the floor and 10-12 inches from the ceiling. Ceiling fans 52 inches or more in diameter will help cool an area roughly 10 feet across. Smaller fans, 36-44 inches in diameter, will help cool areas roughly 4-6 feet across. Before turning on your evaporative cooler, turn on ceiling fans in every room you want to cool.
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If you have floor and table fans, place them in front of an open door or window opposite the evaporative cooler, so they're blowing air out of your home as cooler draws it in. This ensures continuous air motion through your home and is the most effective way to cool several different rooms at once.
Exhaust Fans
Exhaust fans are commonly used in kitchens, bathrooms, and other areas prone to heat and humidity. While some are activated manually, they can also be connected to a thermostat so they activate automatically whenever the heat gets too intense and shut down whenever it cools down. Exhaust fans should be installed high up, close to the ceiling or in it, in order to capture as much heat and humidity as possible.
Attic Vents
Attic vents release heat build up in the upper layers of your home. Attics not only affect by heat rising up from the lower levels of your home, but also from the roof as it absorbs heat from the sun. During the summer, attic temperatures can reach as high as 140 degrees. In excessively hot weather like that, the heat will actually start radiating back down into your home and interfere with the cooling action of your evaporative cooler. If you're having trouble cooling the top floor of your house, even with the evaporative cooler running full blast and the doors and windows open, it may be due to hot air trapped inside your attic. Attic vents are installed under the eaves and the top ridge of your roof, so they can pull in cool air and release hot air. They're an important tool for regulating home temperature and getting the most out of your evaporative cooler.
Conclusion
Evaporative coolers are a great way to cool your home, but they won't work without ventilation. Open up a couple of doors and windows and switch on your ceiling fan before you turn them on. It will keep the humidity down and the cool air flowing.
