From a Masonry Heater chat line ...
Here are a couple of interesting papers on (raw) earth as a phase change material. "Phase change" refers to the additional energy absorbed or given off by water as it condenses or evaporates. The argument is that earthen walls (or raw bricks) have a different relationship to water than fired brick or concrete, which means that their thermal properties will also vary -- in ways that may help to explain the traditional wisdom that adobe and cob are "warm in winter/cool in summer" and otherwise more comfortable than other comparable materials.
Here are links:
The author is John Morony. I don't know much about him; just came across one article awhile ago; the other just now when I looked him up again.
Yes, agreed. Here's a good article about it:
If you scroll down about halfway, to the chart labelled "available water", you can see that unfired clay is listed as maybe 5 or 6 times more effective than brick at absorbing and releasing moisture--which is useful in terms of indoor humidity control. I don't know if anyone has done the math to figure out how much latent heat storage that translates into, though....it's an interesting question.
It's also interesting that end-grain wood the best material listed, better than clay and far, far better than face-grain. But most wood is not cut this way, except for in a cordwood house.
By the way, the Europeans have come up with a new plaster mix that supposedly outperforms clay in terms of moisture buffering:
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