MSU Extension Pollinators & Pollination

Indoor wintering of honey bees at Michigan State University

Michigan State University completed construction of an indoor storage facility for honey bees in the fall of 2023. Honey bee researcher Meghan Milbrath and farm manager Dan Wyns worked with consultants and contractors to modify an existing storage bay into a facility to research honey bee overwintering. The final facility can hold about 40 honey bee colonies, keeping them around 40 to 45 degrees Fahrenheit, with ventilation to remove carbon dioxide from the bees' respiration.

The indoor wintering facility was made by modifying existing stalls in an unheated building that had previously been used for indoor air quality research. The first step was to increase the insulation of the stalls so that it would be easier to maintain a constant temperature. The new insulation was added to the walls, bringing them from R13 to R25, and they were covered with easy to clean NRP. Insulation was added to the large swinging door in the front and to the service door in the back, and all the windows and sources of light were blocked off. Honey bees are attracted to light sources and will fly if the room has lighting. In order to work in the room, employees must wear red headlamps, as the bees cannot see red light.  The ceilings of the stalls were higher than we needed, and the extra space would mean extra energy use for cooling.  We dropped the ceilings by a few feet to reduce the inside of the stall to save energy. 

Once we had a dark, insulated room, the next step was to install a cooling system. Honey bees are animals, so they generate heat as they eat and breathe, even when they are in their efficient winter cluster.  We worked closely with Kimberly Drennan at Hive Tech Solutions to determine what would work best in our situation. Because we were building a building inside a building, we could not use simple weather data to determine our conditions. Instead, we set up a HOBO weather monitoring station for a few weeks to determine what unit would work best, comparing our data to the outside temperatures from Enviroweather. We decided on a KingTech Refer Unit, and worked with Kim at Hive Tech Solutions and our contractor to ensure that we had sufficient load for the wall (160lbs), we had sufficient electrical power, and that it had a place to drain condensation. A small exhaust fan was also hooked up to a timer, designed to 'burp' every 10 minutes to prevent carbon dioxide build up. 

Of course we have to be concerned about back up systems in place, and we hooked up our unit to a generator, and extended our wireless signal so that we could set up an alert system to text if the temperature went outside set bounds or the carbon dioxide was too high. 

In fall of 2023, we received funding from the USDA ARS lab in Tucson to study when the best time to put bees into storage. The first 10 hives were brought into storage in mid-November 2023, and a second batch joined in early December. The bees were moved during a cold night, which is a time when all the bees should not be flying and are in the hive. The fall of 2023 was unusually warm, so this study will have to be repeated many years in different seasons for us to get the best information.