Soil temperature in your area is about 45 deg F year around. If you want the house to be warmer than that, it needs insulation on top, around the walls, and underneath the floor. Minimum six inches foam, ten inches if you want energy efficiency.
Put the foam outside the concrete so the concrete is a thermal mass. Then all the concrete will be warm, including any exposed concrete around exterior doors.
Building codes require all bedrooms to have a second way to escape in case of fire. You cannot escape that requirement because, although concrete does not burn, the contents of the house do burn.
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