I would start limiting his space at night to a small easily cleanable area. Use a cleaner designed to eliminate pet waste as the smell can encourage them to go there again.
I have a crate that I put my dog in at night while I'm asleep, because as well housebroken as she is, she'll still try to go in the house sometimes. This is especially likely if it's cold out and she doesn't want to go out. However, I make it a point to go out with her at night and walk her around. I want to see her go potty even before putting her to bed. I'll also drag her out of bed in the morning whether she wants to go or not. She usually does. I sometimes have to walk her around the yard for 10-15 minutes before she goes. She'll try to sit and stare at me, but if I walk off and call her to me she'll walk over. Eventually, she'll veer off and pee, then I give her a 'Good Girl' and we go straight in. I also made it a point to say, 'Go Potty' while she's peeing. Then if she doesn't want to go, I say it and hope it's formed an association in her head.
Things that make it more likely for a dog to want to go to he bathroom are: just waking up, playing, eating, going for a walk. If you try to do these things before taking her to potty, she'll be much more likely to go.