Can a Home Be Too Tight?

Sometime during your crusade to seal those energy robbing cracks and holes in your home, you're bound to start asking yourself, "Isn't air flow important for a healthy home? Can I take this whole thing to the extreme?"

The answer is that given most of today's homes - no.

While it's true that air flow prevents pollutants like dust and mold from reaching unhealthy levels, a leaky home insures that pollutants keep entering the house (remember the stack effect?)  On the other hand, during a windy day in the winter or summer, a leaky home effectually needs to be re-heated or re-cooled from scratch every few hours, which is a waste of both energy and money. So the best way to ensure that a home is both healthy, safe, and energy efficient is to air seal the home as well as possible, and, if necessary, add some mechanical ventilation to make sure that air cycles in and out of the house at a healthy and consistent rate.  There are now some relatively inexpensive ways to add fresh air ventilation to your home.

In short, your home probably has a long way to go before its tightness is in any way a health hazard.

Ventilation standards like ASHRAE 62.2 are designed for newer, very energy efficient buildings that, by design, have very little air leakage. Chances are, even after significant air sealing efforts, an older home will have more than enough natural ventilation to keep the air in your home healthy. The EPA recommends a rate of .35 ACH (natural air changes per hour — that is, just over 1/3 of the air in your home being replaced every hour; or 3 hours for a full air change) for healthy indoor air quality. The average home has a much higher rate of natural air infiltration than this.

The best thing you can do as a homeowner to ensure that your home is as energy efficient and as healthy as possible is to talk to your home energy auditor about where you should focus your home improvement efforts. But as a basic premise, as the mantra goes, "seal tight, and ventilate right."

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