Hello Don...
I've seen cob structures that flow into the RMH. Bookshelves , little alcoves ,etc. How do you keep this part from becoming part of the thermal mass?
I am not sure that any one would try or want to. Cobb, by its nature is mass form of insulation (U factor instead of R factor) so operates with the "flywheel effect" for both cooling and heating regulation of a space.
I know cob doesn't have any insulating abilities so it would it carry heat to it ?
It really isn't a matter of whether it is insulating or not as it works as a thermal storage battery for both cooling and warmth, unless you are referring to the "bridging effect" that thermal mass insulation suffer from? Thermal bridging is a pitfall of mass insulations but when the mass is large
enough this isn't an issue or if the mass is protected by a breathable insulative layer like
straw clay slip and/or mineral wool. Cobb (or modalities therein) can actually be designed to operate under both parameters of either insulative or thermal storage. Straw Clay Slip is an insulative cobb matrix, that can be employed in concert with a more "dense" blend to achieve both a "thermal resistance" barrier then alternatively and thermal mass layer as well.
Cobb/adobe also works well with other insulative mediums like mineral wools very well, and combining all three, mineral wool layer, straw clay slip layer and then a dense mix would become a super efficient matrix, and examples similar to this are achieve "net zero" levels of efficiency.
Hope that helped solidify a few thoughts for you...
Regards,
j
