Athermanous

from The Collaborative International Dictionary of English v.0.48

Athermanous \A*ther"ma*nous\, a. [Gr. 'a priv. + qermai`nein to
   heat, qe`rma heat: cf. F. athermane.] (Chem.)
   Not transmitting heat; -- opposed to {diathermanous}.
   [1913 Webster]