How to increase hive ventilation for whopping honey crops

Increasing ventilation in bee hives is controversial, but it shouldn’t be. Like any other beekeeping tool, sometimes you need it and sometimes you don’t.

Some people swear by extra ventilation and others think it harms the bees by chilling them. Shockingly, people often say, “We don’t ventilate our own homes, so why should we do it to bees?”

That is sadly naive. In modern times, a house without adequate ventilation will not receive a certificate of occupancy. For residential homes, ASHRAE recommends adding 15 cubic feet of outdoor air per person per minute. And public buildings must replace the inside air at an incredible rate, so fast that it’s difficult for them to comply with energy conservation guidelines.

Why our homes are similar to bee hives

The air in a modern home is always on the move. For example, today we have exhaust fans galore. We eject exhaust air from the attic and showers and baths. We have exhaust fans built into fireplaces and above cooking ranges and clothes dryers. All the air that’s expelled must be immediately replaced by outside air to prevent back-drafting or pulling air from a moldy basement or garage.

Older structures didn’t have such a large air exchange problem because they leaked air around the windows, through the walls and windows, and along the baseboards. Even today, we have some leakage around every door and window, every electrical outlet, every light fixture, and every duct connection. Even so, today’s building materials and insulation are so good we also need to add outdoor air on purpose. And we do. 

Although our homes mostly still have openable windows and multiple doors that aid ventilation, many skyscrapers have few openable windows and not many doors per person using the space. Instead, they have huge fans that pump fresh air into buildings night and day.

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Bees and humans have similar needs

You might think a beehive doesn’t have fans, but it does. In fact, the entire colony behaves like a giant fan, circulating air throughout the hive, bringing in new air, and expelling old air.

The Environmental Protection Agency (EPA) says humans need fresh air to lower levels of indoor pollutants, odors, humidity, temperature, and disease organisms. The same goes for bee colonies. An adequately ventilated hive will have less moisture accumulation, fewer pollutants, fewer disease organisms, less humidity, and less mold. Unfortunately, it all comes with some heat loss.

But with an adequate supply of honey, healthy bees living in a clean hive can stay toasty warm regardless of moderate heat loss. To help the bees rid their home of harmful substances, beekeepers must provide ways for contaminated air to leave the hive and clean air to come in.

How air circulates throughout a hive

The air in a bee hive circulates naturally. Much of the air comes in through the hive entrance or through the screened bottom board if you have one. Some air also leaks through the cracks between boxes or joints in the wood.

Inside, the bees give off heat and moisture just as we do. The air surrounding the bees becomes warm from the bees’ bodies and respiration, then it rises to the top of the hive. This is no different from the warm air in your house that rises to the ceiling or the upper floors.

If you provide an opening to the outside near the top of the hive, this warm air will leave, carrying excess moisture and pollutants with it. As the stale air leaves, fresh air (make-up air) enters the hive at the bottom.

This circulation happens constantly, although the exchange rate will vary with the outside temperature, the number of bees, and factors like wind and humidity. When the bees are actively fanning their wings to dry the honey, the air moves even faster.

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How much ventilation does a hive need?

Every colony is different, so the amount of ventilation you will need depends on the type of hive, climate, local conditions, hive population, and sun exposure. It can be hit or miss at first, but with experience, you will discover what is needed at your location.

Speaking generally, we need less ventilation in dry areas where excessive moisture buildup is not a problem. Desert areas and those with dry winds seldom have a problem with mold or wet bees, but in rainy areas, moisture and mold control can be a full-time job.

Too much heat is a bad thing

We tend to obsess about bees getting cold, but too much heat is just as bad. If a hive gets too hot, it can damage the developing brood, melt beeswax combs, and make workers lethargic.

And because warm air can hold so much moisture, the bees must work even harder to evaporate the water from the nectar. All that hard work generates even more heat, making everything more difficult. When we increase hive ventilation, we reduce the workload on the bees.

14 easy ways to increase hive ventilation

It is very easy to add ventilation to a bee hive. Following are some proven techniques that can be used singly or in combination, depending on how much airflow you want.

• Entrance reducer: During the height of bee season when massive numbers of bees are coming and going, you can either use the largest opening in your entrance reducer or remove it completely. This will increase hive ventilation and ease congestion.

• Screened bottom board: Screened bottom boards allow air to enter the hive from beneath the brood boxes.

• Varroa drawer: If you have a varroa drawer (a wooden, metal, or corrugated plastic tray below the screened bottom board) you can remove it until you are ready to do a mite count.

• Slatted racks can be placed between the bottom board and the lowest brood box. Slatted racks provide more airflow by relieving congestion near the hive opening. You can leave them on all year, either with or without a screened bottom board.

• Vivaldi board: A Vivaldi board allows for increased airflow and moisture control. It goes above the hive boxes.

• Ventilated gabled roof: These roofs have holes on the end much like our attics do.

• Upper entrances: You can drill holes in brood boxes and supers. Upper entrances relieve congestion at the entrance and increase airflow through the hive. If you don’t want your bees to use them as an entrance, you can screen them from the inside. In winter, you can close them with a simple wooden or plastic plug.

• Elevated hive stand: Keeping your hive on a stand instead of on the ground improves airflow.

• Imirie shims: An Imirie shim comes with an entrance notched into it. These shims go between any two bee boxes to provide an extra entrance and ventilation. If you don’t want the bees to use them for coming and going, you can easily screen the entrances.

• Screened inner cover: A simple screened inner cover is my favorite answer to summer ventilation. They also allow you to look down into your hive without the bees coming out for you.

• Ventilation eke: A ventilation eke is a shallow super with screened ventilation ports drilled into it. You can add as many holes as you like and place it above the hive boxes and below the lid.

• Follower boards:  Follower boards give the bees a place to congregate inside the hive. They force the bees to use more vertical space for the brood nest, because they leave only eight usable frames in a ten-frame box. This tall and slender hive structure is more tree-shaped and provides a “chimney effect” that pulls the air up through the hive.

• Inner cover: If you use an inner cover, be sure to use the type with a hole in the center and a notch at one end. The hole in the top lets warm, moist air into the very top of the hive, and the notch allows it to escape to the outside.

• Shade: If you are in a warm climate, by all means, give your bees some shade, especially in the heat of the day. The temperature in the shade can be drastically cooler than in the sun, providing your bees with a better environment for fanning the stored nectar.

Balance one problem against another when increasing hive ventilation

When adding ventilation, keep in mind the downsides of anything you do. For example, openings that are large but not screened could encourage robbing by bees or wasps. 

Also remember that if you live in an area with wind-driven rains, you may need to protect upper openings from rainwater.

Keep in mind that many of these ventilation solutions are most appropriate for hot weather. You may need to seal them up or remove them completely before the weather turns cold.

Frequently asked questions

How warm should a honey bee brood nest be?

The ideal temperature for brood rearing ranges from about 93 to 95 F (about 34 C). Stress, poor development, or death can occur at temperatures above or below the optimum.

Is carbon dioxide built-up important in a colony of bees?

No. Nearly all bees have a huge tolerance for high carbon dioxide levels, so it’s not something that beekeepers need to worry about. In fact, a new paper published in the Journal of Economic Entomology shows how researchers were able to lower varroa mite levels by overwintering bee colonies in high carbon dioxide environments.

Are cross-drafts a problem in beehives?

A draft that goes from one side of the hive to another is generally not a problem, especially in summer, and especially when the air crosses above the honey supers. This helps the bees dehydrate the honey. However, you don’t want a cross-draft traveling through the brood nest, so consider where the drafts will go before you add ventilation.

Rusty
Honey Bee Suite

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