Research: Polystyrene Hive Temperature and Humidity
When there is brood in the hive, the bees seem to like a temperature of 36C (98F) and 58% Relative Humidity (RH). When the temperature gets too hot, they lower it using evaporative cooling. In extremely hot dry or damp weather increasing air flow may be detrimental to the hive.
Beekeeper Rod in the UK reports "Where I live is called ‘a frost hollow’, we live in the Chiltern Hills and we get lower temperatures than most other places in South East England. So knowing internal hive temperatures are vital to know what is going on in my hive. During 2015 I moved my bees over into a High Density (HD) polystyrene hive to see if that would help, as I kept losing my bees over winter. So far looks good, last night the temperature overnight was 5C and this morning the Brood Box (BB) temp was 33.5C, must better than 11C last year in a wooden hive. During recent snow overnight it was -5C and the internal BB temp was 26.5C, which is still very good."
Beekeeper Doug in Australia intends to run two HiveTool systems, "one a poly hive one a timber hive to see the differences."