I got a new colony fairly late last season so I fed them with syrup going into winter and then put on fondant which they've had straight through. I did open it up briefly to put in some more insulation and was a bit worried that it appeared to be dripping down into the frames below but decided to just leave be and keep my fingers crossed! The other colony had virtually two full brood boxes of stores going into winter so I'm assuming they're OK.....
Be careful using insulation for it often leads to lots of mould growing condensation .
Bees handle a week or more of freeze down to minus 10 oC quite happily, so long as theh hive is airy ,dry & the cluster can migrate over stored honey and fondant.
Once the outer bees of the cluster get a feed and they also take a bit down into the centre nest where they " shiver " to produce enough heat that will see the queen hot enough to lay her eggs and also for new sealed brood to hatch . When these fed bees are heading inwards to thee queen , the bees on the outer edges of the cluster make for the stored food and so the cycle continues .... with luck.
It's quite revealing to slip the probe on a digital thermometer with a 1 mtr long wire probe in the middle of the brood box as you give the last feed of the year and see what temperatures you get over winter .
By now 18 March queen in the successfully overwintered hives will be laying like mad .
She seems to reach a really good rate by the equinox ( 23 March ) . About 11 th to 21 st April they begin to start swarming .