Cob RE: "insulation," etc.

[Patrick Newberry]

John,
   This was well said! clear informative... just plain great!

Pat





>> 
> The first thing to be aware of is that Cob is a thermal mass material, not an 
> insulating material.  With all known building materials, there is a trade-off 
> between insulative values and thermal mass.  More mass typically means less 
> insulating, and vice versa.  If one tries to argue the value of cob from the 
> standpoint of insulation, one has already lost the argument.
> 
> According to physics, heat "flows" from one place to another in three ways: 
>  conduction (flow of heat from molecule to molecule within the material 
> itself), convection (flow of heat to (or from) the air (or water, other 
> surrounding medium, etc.)) and radiation (flow of heat from source to sink 
> via "radiation" - without messy physics explanations, this is why the sun 
> warms your skin even when the air is freezing and why you're colder at night 
> under the open sky than under trees).
> 
> R-value is a measure of NOTHING other than resistance of a material to 
> CONDUCTIVE heat flow.  It says nothing about the effect of the material 
> relative to convection and radiation.  It also says nothing about the effects 
> of thermal mass (or lack thereof).  And since Ianto isn't on this list to say 
> it, I'll say it for him - R-value is also a product of the commercial 
> insulation manufacturing industry.  They have made it the be-all and end-all, 
> to the point that codes refer only to R-values and have no appropriate way to 
> account for thermal mass materials and reflective materials.
> 
> It turns out that in most typical dwellings, far more heat is lost by 
> convection and radiation than by conduction - but "insulation" as the 
> building industry knows it only prevents loss by conduction.
> 
> I'll quit for now...does anyone know of a good FAQ on the above topics 
> (thermal mass, physics of heat flow, etc. applied to building materials)?  It 
> would be a good resource to point to when these sorts of questions come up. 
>  If there's not one out there somewhere, let's write one!
> 
> John Schinnerer
> 
> 
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