I know this sounds totally like an ugly cheap idea..But my friend's dad is a total penny pincher.. He did seal off a room of his house by making a styrofoam wall..LOL he literally took giant sheets of styrofoam....Cut out a door hole that can be re plugged into the wall... keeps that room at 80 degrees when the house is at 40! And I believe it could keep it warmer if needed. Of course it isn't pretty, but it's mega cheap!