I am getting ready to install a Drolet eco 65 in my Aunts house, her chimney hangs on the outside of the house. My question is should I line her chimney or Not??? Her chimney is in good condition and was used with a coal furnace prior, which has been removed as of last week. Dealer is telling me that We do Not need to line it, but my gut is telling me to line it anyways. Thanks for any and all help!