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Musings of an Energy Nerd

All About Earth Tubes

Buried ventilation ducts can provide benefits — as long as you avoid a long list of possible pitfalls

The deeper you bury your earth tubes, the better the tubes will perform. In the middle of winter, the soil temperature five feet below grade is significantly warmer than the average winter air temperature. And in middle of summer, the soil temperature is cooler than the air temperature.
Image Credit: Malcolm Isaacs

An earth tube is a buried ventilation duct. The idea behind burying ventilation ducts — the ducts conveying fresh outdoor air to a building — is that the soil surrounding the ducts will warm the ventilation air during the winter and cool the ventilation air during the summer.

Earth tubes can work, as long as:

That said, earth tubes are expensive to install, so they are rarely a cost-effective way to condition ventilation air.

Poorly designed earth tube systems are probably more common than well designed earth tube systems, which is why many earth tubes are eventually capped off and abandoned. If you are considering installing an earth tube, it’s worth learning about what works and what doesn’t.

Get the details right to avoid mold

Earth tubes have a mixed reputation, and it’s easy to find published reports of successes as well as failures. Full disclosure: I’m not a fan of earth tubes. If I wanted, I suppose that I could cherry-pick scary stories from among published anecdotes, but that would be unfair. If you want to install an earth tube, and you do your homework before installing your system, there’s no reason to think that ventilation air delivered by your earth tubes will be damp or mold-infested. Some earth tube systems work well.

The main problem with earth tubes is that even when builders install a well-designed system, the energy savings are so low that it’s hard to justify the high installation cost.

Successful systems

Earth tube systems have been installed successfully in single-family homes as well as large institutional buildings.

Here are links to articles about two successful installations in small buildings:

Here are links to articles about two successful installations in very large buildings:

Deterioration…

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4 Comments

  1. Malcolm Taylor | | #1

    Overly pessimistic
    Surely you could send a child with a brush into a small diameter pipe than four feet?

  2. User avater GBA Editor
    Martin Holladay | | #2

    Response to Malcolm Taylor
    Malcolm,
    You're right. I forgot about all the times I crawled into culverts when I was a kid. It was fun.

  3. User avater
    Stephen Sheehy | | #3

    Response to Martin and Malcolm
    It's important to plan ahead for cleaning earth tubes. If you put a rope in during installation, all you need to do is find a child who's a tight fit, tie the rope to his feet and pull.

  4. Ultimate Air | | #4

    earth air tubes- JM
    Nice article Martin. I'm on year six with my earth air tubes... with no cleaning. I can't scientifically say there has been no problems- but I can say that anecdotally.... I have had no problems. I'll have to find someone with a scope to inspect them I guess. But everything seems to be working fine. And my tube cost was the cheap one. At the beginning of the season is when you have the highest 'capacity'. Moving from winter to summer... ground is still cold... and you are using it to 'cool incoming air'. Summer to winter- ground is still hot and you are using it to 'heat incoming air'. There is roughly a 16 degree temperature swing from beginning to end of season. Could be more or less- depending on tube depth. At $1800- I would still say it is worth it. It eliminates the cost of preheat on a H/ERV... both the up front equipment cost, and the energy use cost over the life. Another interesting point- all cost comparison is based on indoor set temperatures... 68-72 F... If your goal was instead to 'survive' - they would have much higher value as passive means to keep your home from freezing. - Jason Morosko

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