We have lived in our Sundance in -18C weather. Our windows, single pane, do radiate cold but pulling the blinds helps. My wife puts a styrofoam panel over the window on her side of the bed. There should be no air path from the outside around your refer. Look in the back panel and see if some foam may be needed to seal any cracks. Freezing in the underbelly can be a problem, especially with electric heat as primary source. There is a current thread about electric heat and furnace blower to circulate warm air under the floor. We put a skirt around the perimeter in very cold weather.