Cork Insulated Hives

This winter I decided to follow in the footsteps of @pguythompson, Joe Ibbertson aka @BizzleBugs and others with an insulated cork hive. I had a swarm from the summer that was seeking a winter/forever home. I had experimented with them in a homemade horizontal top bar hive over the summer and they had really just bumbled along and hadn’t developed as I had hoped. I could also see issues with the top bar design that were in the long term going to cause me problems. They were an ideal candidate and moved into the cork hive in early September 2022.

Update June 2022

The hive has gone from strength to strength over the spring and what is most noticeable is their performance compared to similar sized hives in the same apiary. The first super was added mid April with the second in early June and a third in late June.

We have since added another 3 cork insulated hives to our apiaries. Two are standard national size and will be placed in a steep north facing valley while the third is a deep box (right photo) which will be kept at our home apiary and now has a proper insulated roof fitted!

Why Cork Insulated Hives?

Insulating a hive in this manner gives a number of advantages starting with a more efficient and stable nest environment. It provides better prevention/reduction of heat transfer by stopping losses and/or gains thus better allows bees to regulate the internal temperature and humidity. This provides optimum conditions for Bees to complete their primary processes – raising brood and making/curing honey.

During the mini summer heatwave of 2022 it was observed that bees in the insulated hives were doing less fanning at different times as if the hive maintained optimum internal conditions better.

Building an Insulated Brood.

Converting a standard national hive into an insulated hive is a straight forward enough process with a few tools. Although the images below show the cork being fixed with bolts subsequent conversions have relied upon PVA glue (both Titebond and Gorilla have proved successful). The cork is 40mm Cork insulation board as shown here although other sources are available.

Across the ends (front and back) the cork is placed on the outside within the recesses and tunnel portals are used to take the bees through the cork. On the sides, cork is placed on the inside and reduces the no. of frames from 11 to 9 in a brood box. My sizes of cork have been:-

  • Ends – 424mm x 137mm. Cut on a table saw with a 30 deg angle giving outside length of 160mm
  • Sides – 374mm x 201mm

Rails are also screwed to the outside (much like Langstroth) to aid with lifting the boxes once the cork is installed.

Protecting the Cork

The cork will weather just fine although the Bees may decide to nibble at it to extract the resin. During manufacture the boards are compressed whilst heated and this leaves a good amount of resin on the surface binding the cork together. This resin is hard for the bees to resist, and who can blame them? In wild tree hives we often see the insides coated in Propolis. So if the cork is treated with a propolis solution then seems to prevent or at least reduce nibbling by the bees.

I’ve tried a number of different techniques for coating the cork:

  • Isopropyl Alcohol (IPA): This is definitely the rapid method. About 14g of propolis added to 80ml of medical grade IPA will dissolve in about an hour glass jam jar with a few shakes. Left overnight once applied any IPA will have evaporated and with it any odour.
  • Vodka: I tried this overwinter and in six months the propolis didn’t break down. So its a no from me.
  • Food Safe Danish (Tung) Oil: Mixing propolis with a good amount of the oil did work but it left a strong odour and oily residue. It took about 5 days in the sun for the cork to dry out and lose the smell. Definitely not a winter finish and probably not one for the summer either.
  • Linseed Oil and a touch of wax: This recipe, handed down like your Aunts Apple Crumble, from Filipe and @pguythompson is one of the most natural. However, it takes 3-4 months to prepare and Guy tells me that he was warming his regularly to 30-35 degs.

a thick honey mixture of Propolis, Linseed Oil and a touch of wax at room temperature. It is then applied warm like a thick paint at about 50degC. Guy explains “I paint it on warm and the main thing is it has propolis, wax and the oil just acts as a thinning medium to get it onto the cork”

At the moment, I’m leaning toward the IPA approach to dissolve the Propolis and then adding some Linseed Oil to aid in application but this is partially due to time constraints.

Insulated Super

The process is the same for a Super. My designs have called on:

  • Ends – 424mm x 62mm. Cut on a table saw with a 30 deg angle giving outside length of 160mm
  • Sides – 374mm x 126mm

Entrance Portals

Due to the cork passage a different type of entrance is called for. The initial ‘Rocket’ design was problematic in that it over ran the cork and a spacer block was required (see above). The new Salbany OS design which returns to the original size and shape will fit on a Super without a spacer block.

For the tunnel there are two options: the Oak Tube as shown above or the cheaper Wire Mesh roll.

Wire Mesh Tunnel

The Wire Mesh Tunnel (WMT) is as yet untested and I’ll be putting it into my first boxes this week (July 2022). The 304 Stainless Steel Woven Wire 20 Mesh comes in packs of 4 x 12″ x 8″ sheets for £11. You should be able to get 6 from a sheet do they come in at around £0.50/tunnel.

To make a WMT you need to cut a piece of mesh just 110mm long and 55mm wide this ensures it sits within the cork and side and doesn’t stick out too far. I find offset snips work best for cutting the mesh as the offset means the handles don’t tangle with the sheet although scissors can be used it will blunt them. Form the mesh around something around 35mm wide. A good sized broom handle does work but leaves it a little tight so I then put the inner edge on the outside to hold it wide. From here you should be able to twist it into place. It works best of you overshoot slightly so that the portal can be placed accurately and then form/adjust the mesh into its best position. I like to leave the join on either the side or bottom so its not the first edge returning Bees meet.

Finally

Don’t forget if you are going to all this effort you will want an insulated roof with an insulated base and/or cold sump floor.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.