Wrapping for winter — when to start and what to wrap with?

Wrap when overnight lows consistently go below 0°C. The insulation reduces the heat the cluster has to produce; you save bees, you save stores. Just leave entrances open enough that they can do cleansing flights on mild days.

Top insulation matters more than side wraps for moisture control. A 5cm foam board above the inner cover with ventilation channel + a Bee Cozy = bulletproof up to –30°C.

Hokkaido approach: full polystyrene insulation box (not wrap), entrance reduced to mouseguard size, top vent. Survived –28°C with no losses.

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