I found out real quick when the temps went down to freezing, in of all places Florida, you have to do more than just turn the heat on in a MH!
Covering all the roof vents with those RV vent pillows makes a BIG BIG difference how much heat 'stays' inside your MH. That and covering 'all' the windows. Including the door window and place a towel at the bottom of the door.
For those few cold days I just went and picked up 5 van windshield sun shades from Walmart. They fit perfectly under the day/night shades without having to use any tape, or velcro.