Winter Ventilation of the hive
During the winter the bees still attempt to keep the temperature at around 320 and a bit higher if they have brood on the boil.
To do this they eat the honey from the stores and by violent movement of the wings their collective frictional heat generated keeps the temperature at the required value. Bees also breathe and the combination of heat and breathing causes water vapour that rises from the brood chamber, upwards.
A normal hive would have a ‘mat’ on top and a ‘hive lid’ over that. Invariably the lid has a metal covering. As a consequence, the rising vapour encounters a cold space at the top of the hive and condenses.
This causes a stream of water to flow from the top of the hive down the sides only to collect on the bottom. Some of the water condenses into the two outer frames on each side of each box and over the winter a mould grows which virtually destroys the wax of the outer frames.
The mould gives off unhealthy vapours that affect the bees and the water lowers the temperature in the hive, especially if it is very cold outside.
All in all, it can be said that if the hive warm moist air can be vented in some way then the nasty problems can be avoided.
What can be done??
A sheet of polystyrene fitted inside the lid increases the insulation
between the hive mat and the metal lid and substantially reduces the generation of water from the vapours.
A hole in the centre of the hive mat allows the moist air to vent into the space above the mat but air becomes trapped under the lid.
If a spacer such as a match stick is placed on each corner of the mat, when the lid is placed on top of the hive (and the sticks) a ‘chimney effect’ is created so that the moist rising air is assisted upwards and out of the hole in the mat and then vented to the outside of the hive.
An entrance reducer can be fitted to the front of the hive. A cut-out of 7mm high and 100mm wide allows the bees to go in and out but prevents mice from getting in. It also increases the chimney effect and aids the venting.
Doubtless other folk will have opinions different to mine and I invite them to
write an article on this topic. One thing to remember is that the location of the hive will have a marked bearing on the need for ventilation. If your hive can be stored inside a protected (from the weather) shed or similar box the need for ventilation may not be necessary.
Hope this helps!