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Thermal Conductivity: Un-fired Earth (cob) vs Fired Earth (Fired bricks)

 
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In this article it has been stated that cob has a low thermal conductivity and for this reason it will absorb heat, retain it, and then dissipate it back out slowly; whereas, "fired brick absorbs and release heat very quickly".

I looked up the thermal conductivity of both cob and fired brick and they are listed at 0.6 W/mK.

Can someone please explain in more detailed why fired earth (fired brick) absorbs and releases heat quickly, while un-fired earth (cob) is better at absorbing and releasing heat. I have been searching on the internet but I cannot seem to find a technical explanation

Thank you and all best!

Michelle
 
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This is my guess, Michelle, not an expert opinion, but the far greater mass of a cob wall compared to a fired brick wall would make a huge difference, even if the thermal conductivity is identical.
 
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Maybe cob has more moisture, which must evaporate/condense during the warming/cooling process. This increases the effective heat capacity, while also regulating the humidity of the building interior.
 
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