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Do Energy Efficient Homes Cause Asthma?

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The British newspaper The Guardian recently published an article on asthma and energy efficient homes, claiming that reducing energy use in homes can hurt indoor air quality (IAQ). But wait! Asthma may not be the only thing to fear with energy efficient homes. A researcher whose report is cited says that poor IAQ also can lead to lung cancer, chronic obstructive pulmonary disease, airborne respiratory infections and cardiovascular disease. Should we be worried? Are those airtight houses going to kill us?

The mythology lives on

I found out about this article when Elrond Burrell, an architect and blogger in the UK, posted a link to it on LinkedIn the other day. He actually showed a revised version of the screenshot you see above because that title is misleading, as indicated by the subtitle.

If you know a little building science, you know what the problem is here. I’ve written about it over and over. In fact, one of the very first articles I wrote back in 2010 was on this topic, the misguided idea that “a house needs to breathe.”

No, a house doesn’t need to breathe. No, energy efficient houses don’t cause asthma. No, the problem isn’t that we’re making houses more airtight.

The subtitle in the screenshot tells you what the real problem is: lack of ventilation. Oddly, they attribute the lack of ventilation to better insulation, rather than the fact that no one thought to install a ventilation system. Not only are they confusing the building enclosure control layers (insulation limits the flow of heat and the air barrier limits the flow of air), but they also missed that mechanical systems are a separate component, and not part of the building enclosure.

Sadly, The Guardian is propagating the same old confusion with this article. I know not everyone can be a building science expert, but this is pretty basic. A lot more people are getting sick because of poor indoor air quality in homes that are not energy efficient in the least. Here are a few reasons why:

  • Leaky homes over moldy crawl spaces or basements that let bad air into the house.
  • Duct leakage brings bad air into the house, sometimes from a dead possum.
  • Moisture problems from flashing causes mold to grow in walls.
  • Unvented space heaters add lots of water to the indoors, growing mold on the walls.

According to a 2007 study on asthma and mold, “Of the 21.8 million people reported to have asthma in the USA, approximately 4.6 (2.7-6.3) million cases are estimated to be attributable to dampness and mold exposure in the home.” In other words, fix the moisture problems.

Airtight homes need mechanical ventilation

OK, let me say this again:

Airtight homes need mechanical ventilation!

I’ve written on this topic a lot. When you seal up a home, you have a better chance of achieving good indoor air quality than you do with a leaky home, but you have to do two things:

  1. Reduce the sources of indoor air pollutants (source control).
  2. Install a whole-house mechanical ventilation system (dilution).

The ventilation system will dilute the indoor pollutants, but a ventilation system with a reasonable ventilation rate can easily be overwhelmed if you fill the house with toxic stuff. The article in The Guardian actually mentioned this when they wrote, “It is important to ensure that adequate ventilation levels are maintained, and indoor air pollution sources minimized, to protect public health.”

It turns out, people have known this for a long time:

“If there is a pile of manure in a space, do not try to remove the odor by ventilation.
Remove the pile of manure.”

~ Max von Pettenkofer, 1858

Again, the problem is not energy efficiency or air tightness. It’s a lack of understanding that a house is a system. In fact, airtight, energy efficient houses can be much more healthful than inefficient, leaky houses.

Allison Bailes, III, PhD
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Posted In: Building Performance, Residential Buildings

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