7 degrees might defeat a light bulb though especially if the high during the day remains under freezing.
Other thing to consider in very cold weather is condensation. We have double pane windows but the windshield was just dripping with it this morning. I actually opened a window and turned on a roof vent fan today for a while despite the cold just to air us out some.
Closing your slides won’t keep the water warm but it’ll make it easier for you to stay comfortable. And it’ll keep the snow off your toppers if that is a concern.
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