We present a comparative study of internal and external thermal insulations in two pilot rural houses in the mountainous cold region of the middle atlas in the Dayet Aoua region, province of Ifrane, Morocco. In both studies we used plastic waste bottles (PET bottles) in cavity walls and roofs. The idea is to increase insulation by reducing convection fluxes in wall cavities using cheap insulating materials. We recorded temperatures in different rooms of each house before and after insulation as well as the ambient temperature outside the houses for a long period of time. Our study shows a significant increase in room temperatures translated in an important reduction of wood burning and better household comfort especially during the cold season.