TYPES OF INDOOR BEE STORAGES AND GENERAL REQUIREMENTS
By Anthony Molitor // Industrial Ventilation, Inc
Types of Indoor Bee Storages
Bee storages can take on many different forms. In the Treasure Valley of western Idaho and eastern Oregon, beekeepers have used everything from existing bulk potato storages, old onion crate storages, cinderblock buildings, or any structure where forced air can be introduced to the hives. Thus far, there is no right or wrong answer to which style of building is best. As we understand it, the key factors for any bee storage are:
1. The ability to provide balanced and consistent airflow to all the hives
2. The ability to maintain a stable and reliable temperature environment within the storage.
There are essentially three air delivery systems to take into consideration when designing and building a storage: Pressurized air floor, pressurized air wall, and a basic cross-ventilation system. There are several considerations when deciding on which delivery system you should choose: First, the size of the storage. Second, the design that will deliver air most effectively. Lastly, cost. All three will provide good airflow to the hives. However, through our experiences in storage for the last 40 years, in nearly all instances an air floor is the most effective means of delivering air into any storage. The air cup vents guarantee that airflow is introduced equally across the entire flow while also working with the natural flow of the hot air rising. The only downside to the air floor is the cost. It is a large investment when looking at a new storage, however, most customers believe the positives outweigh the negatives.
The following are descriptive differences for the variety of buildings used.
Cellars: typically a cool and damp environment
Potato shed: refrigerated systems with humidity and a darker environment but not 100% dark. Also have the ability to purge all the air.
Purpose-built building: specifically designed for bees and will be completely dark
Controlled Atmosphere is a sealed room that is designed to maintain oxygen, carbon dioxide and nitrogen. Can only be entered once proper atmosphere is met. Most expensive type to build.
Refrigerated storage: typically a R-30 or better and no outside air for purge.
This indoor storage facility uses a system that includes fans and perforated metal tubes to keep air flow evenly distributed.
General Building Requirements
BUILDING STOCKING RATES
The number of hives is something that is determined by the customer. As a ventilation company, we are generally given building dimensions and then asked to maximize the number of hives that can be stored inside of those dimensions, given certain guidelines i.e. hive spacing, forklift driving space, etc. In one publication they cite one hive per 30-35 ft3, this is if the building is not air-conditioned (Nelson 1977). In air-conditioned buildings or when colonies are stored as singles, rates can be 15 ft3/hive (Nelson and Henn 1977, Nelson 1982). Beekeepers in the US report stocking rates of 24 ft3 per hive in non-refrigerated buildings and 18 ft3 per hive in refrigerated buildings colonies stored as two deep boxes. Building designs typically incorporate space for trucks to enter for loading and unloading colonies.
VENTILATION & REFRIGERATION
The ventilation and refrigeration systems are directly linked within a bee storage facility. The two must be sized properly based upon the total number of hives in the storage and the total watts of heat each hive consistently creates. Therefore, the amount of refrigeration is the driving force in determining the amount of ventilation airflow within the storage. Through conversations with beekeepers and studying available research, targeting 20 watts/hive creates the proper amount of airflow and refrigeration to mitigate the heat production from the bees. While this sizing is on the higher end of the heat load spectrum, it is not so oversized that the ventilation and refrigeration systems become too expensive and no longer cost-effective. General recommendations for ventilation ranges 0.5–9 CFM (cubic feet/minute) (Nelson 1982). This ventilation rate is variable and dependent on the number of hives per cubic foot in the building, outside temperatures and cooling capacity.
Humidity needs to be controlled within the storage. Excessive humidity and moisture can lead to mold build up, although humidity too low can be equally detrimental to a hive population. Using new computer control panels with precision temperature and humidity sensors allows the beekeeper to maintain very tight tolerances within the storage to eliminate the possibility of too much or too little humidity within the storage. Little published work has focused on humidity. One study overwintered colonies at three different relative humidity ranges: 45-60%, 45-80% and 60-80%. The results showed little difference in weight loss, bee mortality, or spring buildup.
There are two sides to lighting within a bee storage. First, we try and create a lack of light in the storage. Using specialized light block media, this creates a dark interior within the storage while still allowing airflow to exit through the exhaust openings. By blocking as much incoming light as possible, the bees will not be drawn to these light sources and will keep them more relaxed and less active. Second, red lights should be used for the interior lighting as it allows beekeepers to work inside without disturbing the bees as bees cannot see the red color spectrum and will not be drawn to the light.