I've been just above 50 percent wintering success in Colorado. Last winter I insulated my remaining hive and split it come spring/summer.
I'm going into the winter with one standard 2 deep 10 frame and two nucs 5 over 5 squished together. I reused the foil faced foam from last year on the 10 frame and built more insulation panels today for the side by side nucs. I have reduced entrances and a small hole up top for ventilation. Tar paper under the lid for deflecting some of the melting snow with a layer of 2 inch foam up top.
Here's the apiary after finishing wrapping the nucs. It's back into the 60's this week, but as they say, 'winter is coming'.