10 Reasons to Think Twice About Letting Fresh Air Into Your Home

Spring is in the air, which means the season for open windows and fresh breezes is on its way. Sometimes an open window or two is a great way to chase away the stuffiness without resorting to an energy-wasting session with the air conditioner, but there are a few things that you'll want to consider before you invite the outside air into your home. These are ten of the reasons why open windows might be something to carefully consider.

1. It May Not Actually Be All That Fresh – Have you ever thought about how fresh the outside air really is? There are microorganisms floating around in the air along with other unknown contaminants that you may not want inside your home. Depending on your location and factors individual to your particular environment, that fresh air you're letting in may not be so fresh.
2. Allergens – If you or someone in your household has outdoor allergies, you might want to keep the fresh air outside. Allergens carried indoors on a sweet-smelling breeze may actually attack those with allergies and trigger asthma or other similar respiratory problems. These problems can typically be treated with medication, but avoidance of triggering substances is still a sound policy.
3. Pollution – If you live in a larger city, air pollution may be a serious concern when you throw open the windows. You could be exposing your family to dangerous pollutants, even if the atmosphere looks clean and clear of smog. You might not notice the effects immediately, but overall, it’s safer to avoid the outdoor area of any city that routinely issues air-quality warnings. Even pollutants and industrial contaminants that are invisible to the naked eye can be a danger, particularly to those suffering from respiratory problems.
4. Sudden Spring Rains – One downside to opening up the windows to let in fresh air is the chance that you might inadvertently let in the water from a sudden downpour. It’s easy enough to forget that the windows are open when you leave for work, and some rain systems may not be predicted during your daily forecast. The next thing you know, rain is flowing freely through the screens on your window, into your home. Chances are of your home being even slightly flooded are very slim, but that moisture and mess could still cause damage to the frame of the window, as well as to your flooring.
5. You Have an Air Purifying System – The air inside your home is probably much cleaner than that of the outdoors if you have a proper ventilation and air purifying system, and letting those contaminants that could be lurking outside into your home will only make that system work even harder when you do decide to close the window.
6. Letting Heat Into Your Home – More than poor air, opening your windows potentially lets in heat that will force you to turn up an air conditioning unit to bring the temperature back down to a comfortable level. If heating your home is not the goal, which generally it is not when opening the windows, then keep the house shut up and use your air conditioner or strategically placed fans to circulate the air and cool your house. The fluctuations in temperature will make parts of your house uncomfortable, but you can keep everything just right by keeping your house shut tight.
7. Humidity –In particularly humid climates, heavy moisture in the air can make your home feel even hotter and more uncomfortable if you leave the windows open during the warmer months. High humidity can also be problematic for those with respiratory illnesses, so you may be better off to close the windows and rely on your central unit.
8. Bugs, Bugs, Bugs – Screens are good at keeping out big bugs, but tiny ones can still infiltrate your home through an open window. Smaller bugs like fruit flies and even some mosquitoes can end up inside, and tend to be the more annoying bugs out there. Screens may also deteriorate over time, leaving larger holes in them allowing larger bugs to make their way inside the house.
9. Inefficiency – Opening windows may save energy in the beginning, but it’s not a very efficient way to keep your home cool throughout the season. Your air conditioner would have to play catch up if leave windows open for so long that the house becomes unbearably hot during the summer months, and you cannot set a window like you can a programmable thermostat. Also, an open window in one room will not readily cool an adjoining room. You can keep your home running efficiently by relying on your air conditioner to do the job.
10. Environmental Odors – If your home is downwind of a particularly smelly factory, industrial farming site or other source of unpleasant odors, opening the windows will only bring foul-smelling breezes into your home.

While there are times when opening windows is worth a second look, there are also situations in which it's actually more efficient to let the breezes cool your home. Research the air quality in your area, take allergies and respiratory problems into account and consider the predicted daily temperature before opening your windows, and you'll be able to make the best choice for your household.

Resources:
http://answers.yahoo.com/question/index?qid=20100119194246AABcICg
http://environment.nationalgeographic.com/environment/global-warming/pol...