Research: Closing Your Bedroom Door at Night Can Make Your Sick

If you’re having trouble sleeping, the cause may be right under your nose: trapped C02 in your bedroom.

Some fascinating research from Brian Just, reported in the Fall Issue of BuildingEnergy, found that among a test group of 22 homes, almost every home had elevated CO2 levels, when bedroom doors were closed at night. Perhaps most importantly, even in older “leaky” homes, CO2 levels spiked to unhealthy levels with doors closed.


The chart above shows that leaky and tight homes both have similar CO2 pollution levels. Surprisingly, the "leaky" house can actually have even higher levels than the newer home, presumably because the new home has better mechanical ventilation overall.

As Just points out, elevated CO2 when sleeping has been linked to “reduced cognitive function…headaches, fatigue, and a sense of “stuffiness,” to name just a few. And the rooms were not even checked for other invisible pollutants such as VOCs. Those could be even more detrimental to health.

C02 and Health

So what happens when our bodies have to process all that extra CO2 while sleeping?

There is one drawback to ventilation, however, according to a study at the Technical University of Denmark. It dries the air out: "The night-time average values of relative humidity for each subject were in the range between 38% to 69% for the condition without ventilation and 34% to 55% for the condition with ventilation. As expected all subjects experienced lower humidity with ventilation due to the intake of dry outdoor air to the room."

The bottom line, from the same study: "The subjectively assessed mental state and the subjects’ feeling of being rested were significantly greater in the condition with ventilation. The Groningen Sleep Quality Scale showed a tendency for the subjects to sleep better with ventilation, a result supported by the actigraphy data. The subjects also reported feeling less sleepy the day after sleeping with the ventilation running, and their objectively measured performance of a logical reasoning task improved."

The obvious solution to CO2 pollution in the bedroom is easy: ventilation. Clearly, the first, most affordable step is to leave bedroom doors open at night. If this is not a good option, for privacy or comfort reasons, the next step may be to install an HRV or ERV in the bedroom. Room-sized units are available. Zehnder makes one that retails for about $1200, called the Zehnder CA70. It operates at about 85% efficiency and will self defrost down to about 10 degrees Fahrenheit.