The walls were logs. Due to ignorance and economics they were too small in diameter. There were too many leaks in the winter. To try and rectify this situation I placed a vapour barrier on the outside. Put on 2x4 staps every four feet with 1-1/2 in. rigid foam insulation between the straps. Covered this with cedar siding. Were the covering met the projected log ends I used foam to fill in all the gaps. Made a lot of difference in heat retention. The nicest thing about it was the logs would act as a heat sink in winter or summer.
Egon