The wood used in a masonry heater should be dry and seasoned for a number of different reasons.  The first one is for concern of the environment.  A masonry heater, if built correctly, should burn very efficiently, but this efficiency is only diminished when wet wood is used.  When the improper wood is burned, it cannot burn at the high temperatures needed to fully combust.  What this means for the environment is that harmful gases are being released into the air straight out of the chimney.

Another problem and potential danger is the flammable deposits being left behind in your heater and chimney, deposits that can ignite and cause a chimney fire.  Another problem worth mentioning is the decreased efficiency in heating your home.  When the improper wood is used, the heater cannot operate in the most efficient manner, which means the pocketbook will also be thinner.

Only properly dried and seasoned wood  can burn at the highest temperatures to provide the most heat for your home.