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Roof ventilation for tropical areas?

Just inspected 5 of my flow hives and noticed mould build up on the inside timber of the roof, but only in the 2 roofs that didn’t have holes drilled into the side wall of the roofs.
I cover the drilled holes with flyscreen on the inside, so nothing can get in, or out.
We seem to experience a proper wet season this year, which is good all round for a subtropical region that experienced a lot of drought recently.
When we have a wet season, I read that commercial beekeepers migrate their hives inland. Well, that’s not an option for us.
Anyway, I now drilled ventilation holes into all the roofs and covered with flyscreen. Hopefully that will fix the mould.
I am also experimenting with the coreflute sheet in the bottom and top slot, trying this and that.
The bees seem to keep things cleaner when it’s up and they got the SHB under control.
When there are lots of SHB, best to keep the coreflute in the lower position and squash the bastards when the bees chase them down there. Daily if possible. Apithor works great too.
Things change in a hive so quickly, according to outside influences.
Got the SHB sorted for now (I think), hopefully tackled the mould issue by drilling air holes.
Felt to share my experience with unventilated roofs in our subtropical climate.
I guess pine roofs would deteriorate faster than cedar roofs.
How do others cope with the wet?


My suburban Philadelphia neighborhood can get very wet & muggy for periods in the summer. The inner covers or crown boards of my two hives both got mildewed. A little mildew/mold supposedly isn’t a problem for the bees, but like anything else, it’s best not to let it go unchecked.

I gave them a good scrub with mild bleach solution - one could alternatively use vinegar - and let them dry in the hot sun. The stains remain but the spores had to be dead.


A lot of beekeepers paint their hives with copper naphthenate. This is an anti fugicide which prevents the growth of algae and mildew. It is safe for bees. You can search this site for copper naphthenate or google it.
It won’t stop the humidity, your holes should take care of that, but it will protect the wood.

I also use it on fence post now you can’t buy creosote any more.


Someone else told me the same, but mine haven’t done that last winter.

We saw the same here on or little tropical island-location. We removed the board and only had the screened bottom. The bees moved their brood to the top box (no Flow installed yet), indicating their displeasure, it was suggested that the additional light causes troubles in the hive. Then we put the board back and made sure it is completely closed-off so we can cover it with vaseline if we would suspect Varroa, moved the brood down and replaced the entrance reducer with a new one made from metal screen which the bees seem to like because the excessive fanning has disappeared and the entrance is properly guarded again. We hope the honey flow will start soon now in our area, but there is another storm warning. Maybe we still have to make a hole in the roof, we will see when the honeyflow starts. It has been a wet and difficult year for the girls.

Hi Paul, I live in the sub-tropics. I find that my bees do well with only an entrance. I don’t believe that it’s necessary to provide a hole in the roof. I think that a hole in the roof is counter productive to what the bees are trying to do. and that is air condition their hive. The hole in the roof will let hot air in, while the bees are trying to cool it. Therefore they’ll need to collect more water & fan harder in order to achieve their goal.

One thing that will help the bees is to insulate the roof & paint it a cool color, white for example.

One way to test the roof is to put your hand on it on a hot day. If it’s too hot to touch, it’s probably too hot for the bees, which makes their job that much harder.


I think copper naphthenate is not allowed if you want to apply for organic honey status.
Organic - don’t get me started. Flow frames aren’t on the organic allowed list yet.
Still, I start by keeping everything else to organic standard for now.

Hi Jeff. Interesting that you don’t get mould issues without airing the roof area. I can only speak of my very limited experience with only 7 flow hives.
I just drilled about 10 tiny holes into the side, sometimes both sides of the roof. The 2 hives where I didn’t drill holes got mould on the inside of the roof and on the inner cover badly. That’s now rectified.
One of the previously undrilled hives is in mostly shade, the other full sun. No difference between them regarding mould.
Well, it’s a wet time right now, and we are in rainforest bush. Maybe that can make a difference?
You know, even if it’s a total drought, everything is still green here.

I’ve been thinking about the merit of vinyl mats, but as you said, that’s for your situation, not a flow hive set up.
I’m not ready yet to dismiss the flow design, as everything seems to work perfectly well for us. One needs to make adjustments of course for local climate. That’s where my little drilled holes come in for my climate. Works out perfect.
I have no experience whatsoever with traditional hives, so I can just share my flow hive experience here on the flow forum.
To me, the roof space is a buffer zone, where we can get an idea of what is happening underneath the inner cover. As I mentioned before, it’s my communication space with the bees.
Usually the bees consider the roof space outside of their hive, until they need more space, then they include it and build comb. Time for action on our part.
It’s great though to hear input from traditional hive beekeepers, so we can weigh up issues for flow hive beekeepers.
In the end, if I look for a solution to an issue with the flow hardware, I would like to discuss it with flow hivers, not just have the flow hive dismissed as having design faults.
I don’t know if it has faults, it works perfectly well for us, without traditional experience.
Can you believe I emptied 4 flow frames 8 days ago and I had a huge surprise just then to see they are all full and capped again? That’s insane.

+1 for insulation. I had mould in the migratory lids I was using, they were always damp in winter, predominantly condensation I’d assume. Once insulated, no moisture condensing in the lid and no mould as a result.
I’ve retired my Flow lid and crown board, replaced with insulated migratory lids.
Following Jeffs recommendation I’ve also closed the roof vents. The hives are in full sun with no entrance reducer and doing are fine. I find reducers restrict the bees ability to properly clear the bottom board and I find wax moths living in the debris trapped in the reducer when I inspect. Im going to try a central reducer with entrances on the sides for a change.
Is mould a problem anyway?

People say mould is not a problem for the bees, but I wonder from what point on mould shows excessive moisture. For a start, it would encourage SHB. Paired with a cold snap, we may see chalk brood.
I am keenly looking at all experiences and opinions everywhere.
I know I live near the flow inventors, and our region may well have an influence in design.
For us the design works really well. Love the coreflute that can be up or down. Experimenting and observing.
We take notes on everything and are learning what is most contributing to the colonies at a time. There are no rules, there is only what works best at a given time. And how we understand what stage a colony is at.
There are no hard fast rules in beekeeping it seems.
In any case, I love the look of the flow roofs and use the roof space for feeding baggies and communication. Even to let them clean out a frame I cut honeycomb of, or a frame I want to cycle out.
Maybe flow beekeepers will come up with their own rules once it all gets more established and used.
Or maybe it’s just a local great thing.
In any case, I will be watching this space.

Hi @skeggley, I think that the central entrance reducer is a great idea. I recently started doing that myself. That was after a bee customer turned up with a brood box that included one. He got the idea online. He said that the reason for the central reducer was so that the bees draw air in one side & expel it out the other side.

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I see them do this on my “normal” wide entrance with no reducer (you can feel the air coming in one side and going out the other - or see it if you hold a thin strip of newspaper up to the entrance) but on my floors that come with a narrower entrance (no reducer- about 15cm across), they don’t have the width to do this. Yet I understand that 15cm2 is an ideal sized entrance…

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Hi Dan, it’s great that you experienced that. Something that I have never tried. I recently read that it’s more obvious during the night while the bees are ripening that days honey. I agree that 15cm is an ideal width. With the ones that I reduced in the center, I left about 75mm on each side. I don’t know how the bees figure out which side is in & which side is out.