The House of a Million Breaths

Researchers tested our home's air-tightness before installing air-quality meters and data loggers.

Researchers tested our home’s air-tightness before installing air-quality meters and data loggers.

If the average human takes about 20,000 breaths per day, and Alex and I are home about half the day on average, that means we fill our house with about 600,000 exhalations per month. Add those of our new puppy, Beatrice, whose main activity is to sit around and breathe 23 hours a day (and run around like an insane monkey the other hour), and you start to approach a million breaths.

That’s a lot of hot, humid air. Where does it all go?

Researchers from Washington State University have chosen our house for a study that will determine just that.

They’re placing sensors in about fifty Puget Sound houses to monitor key air quality indicators. Their equipment also tracks when ventilation fans are on and when doors are open. The goal is to find out how ventilation works in today’s newer, more airtight homes.

Poor air quality can cause tiredness, the inability to concentrate and make decisions, and even serious illness. Avoiding products that emit harmful pollutants into the air is important, but to ensure that your indoor air quality is healthy, ventilation is required.

What’s Being Tested

Air quality professionals can measure a range of factors, including mold spores and volatile organic compounds (VOCs), but this study focuses on one of the best and simplest indicators: carbon dioxide (CO2).

We exhale CO2 with each breath, and levels rise if ventilation is insufficient. CO2 itself is not toxic, but high concentrations, above about 1,000 parts per million, indicate that a room may be under-ventilated and could be harboring other, more toxic compounds.

Getting Ventilation Right

Testing your air can help you save energy. High levels of CO2 indicate that you may need to increase your ventilation, but unusually low CO2 levels may tell you that you can cut back. Over-ventilating your house can’t harm you, but it may be wasting energy by allowing too much conditioned air to escape, undermining the effects of good insulation and an air-tight building envelope.

I’d love to get a controller for our ventilation fan that turns it on when a certain CO2 level is reached. Unfortunately, the cost is prohibitive.

How many breaths does this puppy take every day?

Beatrice, have you been breathing again?


Representatives from WSU have asked us not to share any results until the study is complete, but that doesn’t stop me from checking the displays on the little meters they’ve placed throughout our home. It’s very interesting to see how CO2 goes up when a door is closed and our ventilation system is turned off (one of the scenarios they’re testing).

What I can say now is that we have a very tight house, and the difference between ventilating and not ventilating is fairly dramatic. One thing is for sure, our houseplants are happy: When CO2 rises, they start growing! In fact, if you ever notice your indoor air feeling a bit stuffy and your plants growing like mad, it may be a sign that you should test your air.


6 thoughts on “The House of a Million Breaths

  1. Nice study and good observation about the houseplants. Plants should eat the CO2, but in my experience, even a large number of houseplants can’t consume carbon dioxide fast enough to compensate for all that human breathing.

    • Quite right. I really have noticed our houseplants flourishing during this air quality study, but I’m sure that even with the extra leaves, they’re not pulling very much CO2 out of the air.

  2. Hey Eric… It would be so cool if your energy management stuffs had the ability to stream live data to your website. Kind of like a dashboard of consumption vs. not consumption?? Anyway, then we could congratulate you when your numbers were good, and tell you to turn out the lights when the numbers were bad. 🙂 We need to have you and Alex come visit us in West Seattle and see the kids. –Bill

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