Just Open Your Windows?
by Building Inspector and Indoor Air Specialist, Dan Schilling
© Copyright 2002 Residential Inspections LLC, All Rights Reserved
When it comes to indoor air quality (IAQ), some think that if you open your windows your indoor air problems will be solved. This is not at all true. However, we should not lean in the other direction either. Unfortunately, some doctors are telling their asthma and allergy patients to stay indoors, close their windows, and use the air conditioning only; which can be equally as bad, if not worse. As with most things in life, there is a balance which is achieved through the application of knowledge. This article is written to educate you as to the benefits and limitations of opening your windows, as well as, how to strategically use your windows to your best advantage.
Disadvantages of opening windows as an IAQ solution
Heating, Cooling, and Inclement Weather
Perhaps this should go without saying, but if you are heating your house in the dead of winter, you're not going to be leaving your windows open at the same time. Similarly, when you are cooling a home in a hot or humid climate, you obviously will not be leaving your windows wide open. Despite the lack of fresh air, the cost of leaving your windows open during inclement weather, or while heating or cooling, would be nonsensical. We need fresh air, but we also need to be smart about how we get it into our homes.
Anyone living on earth understands there are plenty of people on this planet who are less than honest. From a home security standpoint, leaving the windows open on your house when you are not home is typically unwise, and in some areas, may not be the best idea even if you are home.
Established Air Flow Patterns
If you do open a window for ventilation, you should also understand the limitations of doing so with respect to IAQ concerns. When you open just one window, you will have an established air pattern that will allow the warmer air to move in or out of the window at the top of the window opening and the cooler air to move in or out at the bottom of the opening. With the air exchange taking place only at the window, this does very little to benefit the entire air supply in a home. A better scenario is to open several windows for cross ventilation. However, this too has its drawbacks in the big picture of the house's air. The reason again is air flow dynamics. If there is no method of mixing the air around the house while the windows are open, such as with room fans, ceiling fans, or an air handling system with forced air ducts, then there will be distinct air patterns established from one window directly to the next. This means that only about 10% to 20% of the air in your house is actually being exchanged. This is no where near enough to be a solution to IAQ problems; not even in the short term.
When you realize that a person can die in a matter of minutes if exposed to vehicle emissions in a closed garage, then it should be no surprise that living next to a massive amount of vehicular traffic on a busy street or highway can cause health problems as well. I have known and worked with individuals who have had to move away from busy streets or from next to a bus stop in order to escape the effects of the concentrated diesel and gasoline combustion emissions. Obviously if you live near heavy vehicle traffic, there will likely be periods of the day when opening your windows could invite high levels of combustion pollutants into your house.
Allergies and Asthma
Depending on the season, opening your windows may be disadvantageous if you suffer from allergies or asthma. If there are high levels of mold spores, ragweed, tree pollens, etc. in the air outdoors, they can enter the indoor environment when the windows are opened. Typically, the best time for suffering individuals to open windows is at night, when the winds die down and the airborne allergens are likely to be lower. If you suffer, you should probably keep track of these allergens according to their respective seasons and use wisdom when opening your windows. However, you should also understand that it is not normal for people to suffer from inhaling natural amounts of harmless outdoor allergens. The reason people become so sensitive to these harmless substances is much more likely due to their high level of exposure to indoor air pollutants, which are much worse in chemical design and can easily exceed outdoor levels by up to one hundred times. It is my belief that it is this exposure that damages our immune systems and causes them to react so unnaturally to substances that would otherwise never bother us. If you suffer, I highly recommend that you allow yourself the opportunity to get better by first and foremost controlling your indoor air.
Replacement of Electrical Ions
Opening your windows will not allow the entry of sufficient amounts of electrical ions, which are essential to purifying your indoor air of particulate matter, the invisible but physical particle pollutants that float in your air. This is especially true if you have screens on your windows to keep bugs out. Electrically speaking, ions become grounded out and discharge their energy when they come in contact with anything connected to the earth. This includes your house, which also happens to include your window screens. The only feasible way to get sufficient amounts of ions indoors is to use an air purifier that replaces your ions 24 hours a day. (To learn more about the benefits of electrical ion replacement, see the article called “Understanding Electrical Ions.”)
Replacement of Activated Oxygen (Ozone)
Opening your windows will not allow the entry of sufficient amounts of ozone, essential to purifying your indoor air of chemical gasses and other odors. Even if you had every window in your house wide open, and there was a sufficient breeze to push fresh air into your house and push the stale air out, it would still be impossible to get enough natural ozone to come indoors for a significantly beneficial effect, much less a lasting effect. Furthermore, ozone has an estimated half life of as little as 20 minutes to as short as 5 minutes. This means that from the very moment you close your windows, the benefits of ozone immediately begin to diminish. The only feasible way to get sufficient amounts of ozone indoors is to use an air purifier that continuously replaces your ozone to maintain natural levels. (To learn more about the benefits of ozone replacement, see the article called “Understanding Ozone.”)
The advantage of opening your windows is oxygen
Most people do not realize that there is a limited amount of air outdoors and it gets breathed over and over and over again. The nice thing is that nature constantly purifies the air outdoors with perfect amounts of ions and ozone, and it also creates the perfect amount of oxygen to sustain us breath after breath. In our sealed up, air tight, energy efficient homes, the situation is much different. We not only have a very small amount of air to breathe inside of a building, but we have nothing indoors to replace the missing ions, ozone and oxygen to our indoor air. With new air purification technologies we can now replace the missing ions and ozone, but we still need a viable solution to the problem of depleted oxygen. The primary advantage of opening your windows just happens to be the increased oxygen level indoors.
I find that far too many people keep their windows closed all the time, especially when heating or air conditioning. They breathe the same re-circulated air over and over again, and then pay for it in both intermittent and long term health problems. People need to realize that re-circulating air that is rancid provides no health benefit whatsoever. Re-circulated indoor air is distinctly different from recycled outdoor air. Furthermore, the few dollars saved in energy by keeping windows closed, is not to be compared to the thousands of dollars paid in health care, risky medications, and the loss of productivity.
Have you ever been warned not to put a plastic bag over your head? Obviously you would suffocate due to the small amount of air inside the bag. Your house is similar to a large plastic bag with a very limited amount of air inside. Not only is your air supply limited, but each person in your home will consume approximately 2,500 gallons of air each day. This is approximately 22,000 breaths of air for each person. Every time a person takes just one breath, it degrades the quality of the air indoors. Now multiply that times how many people live in your house; or the rapid affect of air degradation when company comes to visit. The very moment you close your windows, the air inside of your home starts turning from fresh to rancid. As humans and animals inhale and exhale, the oxygen levels plummet and the levels of poisonous carbon dioxide increase. These higher carbon dioxide levels cause headaches, fatigue, attention deficit, unrest even after sleeping, as well as, many other indoor air related symptoms that people do not readily connect to the poor quality of the air they breathe in indoor environments.
Newer commercial buildings, most of which have no operable windows, are required to have a small amount of oxygenated air brought in for the occupants through the heating and cooling system, however, many of these systems are mechanically operated and quit working without being noticed by service companies, much less the occupants. As with residential homes, the occupants simply put up with their suffering or use risky drugs to mask their ill symptoms. Furthermore, older commercial buildings have no provision at all for oxygenated air and almost every residential home lacks a source for outdoor air.
How to use your windows strategically
Typically, when people do open their windows, they only open them when the weather is nice out. This is a big mistake. Think of your house as if it were a toilet. Certainly you would not use it over and over again without ever flushing it. Even if you happen to be using the best air filters and purifiers available, the air in your home still needs to be flushed on occasion. Fortunately, flushing your house is a simple process. Oddly enough, it is easiest done during those times when we would most likely not do it at all, such as during bitter cold weather, or when it is extremely hot and humid outside.
The idea of flushing your house is to quickly get rid of rancid indoor air and bring in a copious amount of oxygenated air. Of course this is not a problem when the weather is nice outside and we can leave the windows open for a while, but what about when the temperature outdoors is extremely different than indoors? How do we do this without allowing our homes to get too cold or hot?
Due to the fact that air pressure, vapor pressure, and temperature always seek equalization, the process of flushing your rancid house air is very easy when the temperature outdoors is extremely different than that of the indoors. To accomplish a good flushing during these times we need only to briefly open at least one window in each room, all at the same time. In practically no time at all, a large amount of fresh oxygenated air will enter and replace the spent air. Just about the time you get the last window open, you can already start closing them. If you happen to be heating, all you will need to reheat is the air that just came in because the house and everything in it did not have time to even get cold. One quick cycle of the furnace and the new air will not only be re-warmed, but will now have more oxygen in it for the benefit of the occupants. The same is true if you are cooling, as the new air will rather quickly dehumidify and cool off. If you happen to be using an ozone replacing air purifier, the added oxygen will actually help your purifier to work more efficiently. This is because ozone is really nothing more than temporarily activated oxygen.
I recommend that you make a practice of flushing your house whenever your air starts to feel the slightest bit stuffy. This is usually easy to tell when you first enter your house from the outdoors. After breathing clean fresh outdoor air, you will typically be better able to observe how bad the air is inside your home through the sense of smell. In fact, if you are smart, you will begin paying close attention to the quality of the air every time you step into a home or building. Lastly, if you are not yet using an ozone replacement air purifier, house odors will be another distinct sign of the need to flush your house. These odors could be from off-gassing chemicals emitted from new building materials or carpet, from cooking, smokers, pets, and humans. Ideally, the air inside your house or workplace should not have any odors in it…period.
Some people are installing what are known as air-to-air ventilators in their homes in an effort to bring in some oxygenated air. I do not recommend these devices, as they can actually poison your air or damage the structure of your home if maintenance is overlooked. At the time of this writing, in every home I have inspected with these devices installed, the regular maintenance was not performed. (To learn about the advantages vs. dangers of these systems, see the article called "Air-to-Air Exchangers".)
One other solution to improving oxygen levels in your home, at least partially, is to install a make-up-air vent in your home. Unless your home is quite new, you probably do not have a make-up-air vent as they were not required by code until just recently. A make-up-air vent is worth every penny it costs to install. A make-up-air vent does not bring in oxygenated air on an as need basis, but it does bring it in whenever air is being exhausted from the house to the outdoors through things like fireplaces, furnaces, water heaters, bathroom exhaust fans, kitchen exhaust fans, and clothes dryers. (To learn about the critical importance of these vents, see the article called "Make-Up-Air Ventilation".)
The bottom line: Opening windows is helpful, but it has not and will not ever be a viable solution to the indoor air pollution problem. Unless you live in an area where you can leave all of your windows open, without screens, 24 hours a day, all year long, you will need to practice some strategies for opening your windows in combination with air filtration and replacement of your missing ions and ozone.
with those you care about.