propane heater in trailer while traveling

I have 2 dogs. One is a lab/ spaniel cross that lives in the house with me and he then doesn't grow much hair. Put him outside on a cold day and he is barking to come back in quickly. The other dog is a German Shepard/ St Barnard cross that lives outside. She grows a thick coat of hair and loves to play in the snow. She has 2 dog houses, a wooden one that is cool she sleeps in during the summer, and in the winter someone sold me a house that had been built out of a old not working Deep Freezer. She loves that in the winter and sleeps comfortably in it on nights well below 0f.