Beehive Wraps for the Winter
Winterizing Bee Hives
Reading Time: 5 minutes
By Patrice Lewis – Beehive wraps for the winter help keep the hives warm and can make or break the success of an apiary, especially in northern climates.
Incorrectly wrapping a hive can be fatal. Consider the sad experience of one novice beekeeper during his first winter. “I was convinced the bees needed to be protected from cold, wind, rain — everything,” he relates. “I purchased foam insulation and boxed the bees in completely, except for the hive opening at the base. The hives suffered terrible condensation, and it killed the bees.”
The following year this beekeeper didn’t wrap his hives at all but merely moved them to a protected location out of the direct weather. The hives made it through winter just fine.
Does this mean wrapping is unnecessary? Yes and no. As with almost anything in the beekeeping world, there are passionate proponents on both sides of the issue. Many unwrapped hives overwinter just fine. However, a properly installed layer of insulation in cold climates can make things less stressful for the bees during the winter.
As a rule of thumb, many experts recommend wrapping hives if you live in a USDA Zone 5 or lower. The trick is to wrap your hives in such a way that they don’t get fooled into thinking it’s spring.
Winter in a Hive
What are conditions like inside a hive during cold weather? Keep in mind that bees are active all winter long (they don’t hibernate) and have one single goal: to keep the queen alive. They do this by heating the interior.
Once the outside temperature drops to about 55 degrees F, the bees start clustering around the queen and vibrate their wings to generate warmth. The colder the temperature, the tighter the cluster. They do not heat the entire hive, but only the discrete cluster where they huddle in the middle with the queen. They maintain a temperature of about 96 degrees F at the center of the cluster, and about 41 degrees F at the outer edges. (Below 41 degrees F, bees go into torpor conditions and can’t move.) Inner bees rotate with outer bees so no one gets too worn out. The cluster itself moves around the hive, eating honey as it goes.
Ventilate Ventilate Ventilate
A winter cluster produces moist, humid air that must be vented, which is why a hive should never be completely sealed. Providing an upper entrance facilitates exhausting (venting) the moist air and a route for bees to take “cleansing” flights to rid the hive of excrement.
The critical thing about winterizing hives is ventilation. You’re not trying to make the hive airtight. Condensation is one of the biggest killers in winter.
To prevent moisture buildup, hives need a ventilation hole for airflow. It seems counterintuitive to have a spot where cold air can get into the hive during winter months, but bees handle cold air better than freezing water dripping on them. Beekeepers must walk a fine line on winter beehive ventilation. Too much, and the bees can’t keep the hive warm; too little and condensation can build up. A little condensation is fine since it gives the bees a source of drinking water, but too much condensation rains ice water on the bees.
Depending on the climate, simply propping open the roof with a shim might result in too much open space. A better alternative may be to drill a one-inch hole in the top corner of the upper brood box or use an Imirie shim, which is a rectangular wood frame about ¾ of an inch high, with a beehive entrance hole cut into one end.
Types of Beehive Wraps for the Winter
There are many different ways to wrap hives, ranging from cheap to pricey.
• Hay bales. These can be stacked around three sides of the hives, leaving the entry side open.
• Tar paper. A common sealant used in construction, tar paper is not just cheap, but its black color absorbs the sun’s heat and may raise the temperature inside the hive by a few degrees. Affix the paper to the hive with a staple gun, and use a utility knife to cut the paper away from ventilation holes at the top and bottom.
• Styrofoam board. This differs from tar paper in that it works to retain heat within the hive rather than absorbing heat from the outside.
• A bee cozy. These are pre-made fiberglass-filled plastic-covered sleeves that fit over the hive box. They are both waterproof and breathable, which helps keep temperatures stable and humidity levels moderate.
• EZ-On hive wrap. This is a pre-made wrap of vinyl-coated polyester with insulating foam secured with Velcro. It’s considered the easiest wrap to use.
• Polystyrene hives components. These are boxes fitted with built-in plastic frame rests and metal latches to hold insulated components, which offer added protection against weather extremes.
• Thermal reflective bubble wrap. Cut to size and secured with Velcro, this is an easy do-it-yourself option.
Whatever option you choose, make sure the wrap is snug against the outside surface of the box; otherwise, bees may crawl between the box and the wrap, get stuck, get chilled, and die. It also helps to make sure the boxes are stacked perfectly square, which not only facilitates wrapping but doesn’t leave gaps between the box and the insulation where bees may crawl.
Even if you choose not to wrap the hives, consider insulating the cover assembly, either by inserting a one-inch piece of foam insulating board or by using an insulated telescoping cover. If using fiberglass as insulation, protect it with a screen, so the bees don’t attempt to remove it. Hives, just like homes, lose most of the heat through the “attic,” so insulating the ceiling offers some protection and helps reduce condensation. A quilt box can also help with condensation.
If your area sees wind in the winter, creating a wind block is important, such as an existing wall, stacked hay bales, or placing hives in an open-sided shed or barn.
Snow is an excellent insulator, so snow piled on top of hives may be beneficial as long as the hive openings are clear enough that bees can come and go.
For those who haven’t made up their minds about beehive wraps for the winter, consider running an experiment: wrap some hives, and leave others unwrapped. The success or failure of the two options may convince you whether to wrap during future winters or not.
Bees in the wild are equipped to handle winter, but when we keep them in man-made hives, we may need to give them a little extra help to make it through the coldest months.
What type of beehive wraps for winter are your favorite and why? We would love to hear from you in the comments below!
Originally published in Backyard Beekeeping October/November 2021 and regularly vetted for accuracy.