Updated: Sep 15
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? Doesn't my house need to breathe?"
The answer is houses don't need to breathe, but humans do!
The truth is that a leaky home provides no assurance that indoor air pollutants are properly leaving the home: during periods of calm weather with no wind, for example, air can sit stagnant in a "leaky" home for days. On the other hand, during a windy day in the winter, a leaky home effectually needs to be re-heated from scratch every few hours, which is a waste of both energy and money.
The best way to ensure that a home is comfortable, healthy, safe, and energy-efficient is to air-seal the home as well as possible and then use proper ventilation, like good bath and kitchen exhaust fans to remove moisture and cooking byproducts out of the house. For very tight homes, it may be necessary to install a whole-house ventilation system like an "ERV" or "HRV" (Energy Recovery and Heat Recovery Ventilators). But as a basic premise, our mantra is, "seal tight and ventilate right."
That said, if you happen to live in an old, leaky home, and aren't ready to install an ERV or HRV (which captures the heat from outgoing air and transfers it to incoming air to minimize heat loss during the heating season, and vice versa during the cooling system), the truth is that 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 largely designed for newer, very tight, energy-efficient buildings. Chances are, even after significant air sealing efforts, an older, leakier home will still have 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 older home has a much higher rate of air-leakage than this.
The best thing you can do as a homeowner to ensure that your home is as comfortable, healthy, and energy-efficient as possible is to hire a professional home energy expert who will show you the "low-hanging fruit" in your house where big improvements can be made cost-effectively. You'll save yourself a lot of time, money, and headaches choosing this approach, versus guessing what the problem is and throwing money at it.