Renting A Cold House! What Should I Do?

[George Jones]

Happy New Years, BP family! It's been a while since I posted, but I have a question. About 5 months ago, I rented a 1-level house in Southeastern Michigan. Nice 3BR home. The problem is that it is so poorly insulated that the 2 back bedrooms are basically unusable due to the coldness coming in through the floor, the closet, and the baseboards. In fact , there is so much air coming into the house as a whole that the furnace is constantly, constantly running - costing us a fortune just to keep it comfortable in here. I'm not sure how difficult it is to insulate the underside of the house (as well as the rest of the house). But, my question is this: If the landlord is unable or unwilling to fix this problem, What should I do???