I too have been heating my garage(30x30)with a big woodstove for 20 years.I light it about 1 hr ahead of work time.I wear some insulated coveralls til it warms up.When done working I,ll throw a big log in and choke it back for the next day,then it,s still warm when I get off work.It does hit -30,s here,but not to often.Oh,I use insulated pipe,so no worries about unexpected fires.