The best type of vestibule is a long, narrow passage lending into the hillside, and it should be closed by doors at both the inside and outside ends. If possible the vestibule should be built and protected so that the temperature within the vestibule will never fall below freezing. In the building of the vestibule, also, the beekeeper should consider the ease with which the bees may be carried in and out of the cellar.
As has been mentioned previously, the cellar must be well drained, either by natural or by artificial means. No stagnant water should be allowed to remain in the cellar, although at the higher temperatures of the best cellars this does less harm than it does in cellars that are too cold. Some beekeepers have advocated having a stream of water flowing through the cellar, and this will do no harm in warm cellars, and it may serve to assist somewhat in maintaining an even temperature.
One of the most serious faults of bee cellars is in providing for too much ventilation, resulting in great fluctuations in temperature. In a cellar which maintains a temperature of 50° F. or more there is little need for ventilation, for the Was then need little oxygen and only a small amount of carbon dioxide is given off. Other things being equal, the colder the cellar, the greater the need of ventilation. If poor stores are in the hives, the bees will need more ventilation than will be desirable when good stores are used. In a warm cellar in a sandy hillside no ventilating shaft need be built.
In any event, one shaft 6 inches square running through the ceiling of the cellar to the outside will be sufficient for any cellar that is fit for the wintering of bees. During the coldest part of the winter the interchange of air between the inside of the cellar and the outside will be materially increased by the great difference in temperature and this one ventilator may be entirely or nearly closed. During the milder weather of the fall and spring this amount of ventilation will do no harm. The top of the ventilating shaft, which should extend at least 6 feet above the outer roof, may be painted black in order to induce greater movement of air when the sun shines. The shaft should be so arranged that it does not admit light to the cellar.