One year we experimented with some hives warm way and some cold. All other factors (location, size of colony) equal. The warm way colonies got off to a much quicker start and seemed to be about 2 weeks ahead of the others when we did our first spring inspection. Last year we were wintering 3 nucs in National brood boxes with full-length dummy boards and polystyrene filling the spaces where frames weren't needed. Naturally, we couldn't do these warm way as the bees would have been shut in, so they were cold way but with insulation. They all came through and were strong in the spring. Did the polystyrene prevent the sun's warmth getting through the sides? If so, the insulation seems to have made up for it.