Leave the Windows Open or Shut?

Q: We own a weekend retreat in Massachusetts that is 75 feet from a river. My wife and I are at odds over whether to leave the windows open when we leave. She likes to leave them open a crack “to let in the air.” I tell her she is only letting the moisture in.
– Clem Lanza, via e-mail

A: First of all, let’s assume that the way you are leaving the windows open doesn’t allow rain or snow to sneak in. If it does, then you should definitely close them. Water leakage can cause permanent damage to the cabin, of course, as well as create a fertile breeding ground for mold. Also, do the windows lock when they’re in the open position? If not, security is another argument for keeping the windows closed.

Your wife is correct that opening windows is a good method of ventilation and can be an effective way to keep the cabin fresh and help release harmful agents generated by wood smoke or other combustible activities. The Environmental Protection Agency and the American Lung Association both recommend ventilation as a way to improve indoor air quality.

If your concerns about moisture are about humidity and you have no leakage problems, you really needn’t worry too much beyond what makes you and your wife feel most comfortable. The biggest moisture demon – mold – is usually caused by leaks, not by atmospheric humidity.

Neil Carlson of the University of Minnesota’s Department of Environmental Health and Safety says that season and weather dictate what effect open windows will have on your cabin. On a hot summer day, for example, if the air outside is more humid than the indoor air, that humidity will indeed come indoors. In the winter, the outdoor air is usually drier so the opposite would be true.
    
Either way, as long as your cabin is not an airtight, hermetically sealed environment, the difference between indoor and outdoor air is going to be slight.

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