Hey-bee it’s cold outside

151206 BroodMinder 2

Placing a BroodMinder sensor on top of Mars on December 6.

I received my BroodMinder “Health Telemetry Sensor” devices this past week. It was a good week to have temperature and humidity sensors, as it’s been colder here with some hard frosts overnight multiple days in a row. Mind you, this is Virginia, so it’s been warm with the bees flying in the afternoons. This weekend we’re expecting temperatures near 70 (21 C), so don’t feel too bad for me or the bees.

I thought I would share some initial experience with the device and some changes I’ve already made to the hives as a result of the readings.

If you haven’t seen the “buzz” on this: BroodMinder started as an Indiegogo campaign looking to raise $20,000 and sell at least 500 devices. The device records temperature and relative humidity, and is designed to sit on top of a Langstroth box. Knowing how warm and how wet the top of the hive is should provide a good indication of how the bees are doing, especially during winter months when the bees are hunkered down inside.

The campaign was successful, and you can still order the device from the Indiegogo site. The first devices shipped on time the week of December 1, as promised. Developing hardware, especially for a new idea, never quite goes as planned, so shipping on time is no small feat. According to the latest update from the team the domestic orders (in the U.S.) have shipped and the international shipments are on their way. I am still not sure how best to “winterize” my hives: what is the best opening size? should I insulate the top? is upper ventilation really needed? So I ordered two devices to gain some insight into how my Langstroth hives were doing. Excessive water vapor is said to be a prime killer of hives in the winter, so I was especially interested in seeing the humidity settings.


BroodMinder in Hive

The bees checking out their new sensor device.

You can tell the BroodMinder team has experience with electronic devices. The packaging is clean and simple, the installation is a breeze, and everything “just worked.” The one snag was that Apple had not yet approved their mobile app, so I had to use a version made available via Apple’s TestFlight program. This week Apple approved the app so you can download it from the App Store.

My first device arrived on Saturday. I sent a note to support@broodminder.com in the morning and by mid-afternoon had installed the app via TestFlight on my iPhone. Sunday afternoon I placed the device on top of our Mars hive, as shown in the picture at the top of this post. The packaging has a small tab that sticks out the back so you can see the device id without opening the hive.

The app is very basic, but gets the job done (see the BroodMinder Support page for a description of the app). After I installed the device the numbers looked good: around 3:30 pm the temperature was 64 F and the relative humidity was 68%; around 4:30 pm these were 61 F and 74%. One drawback of the current setup is that you have to physically visit your hives to record the reading on your phone. Hopefully this can change in the future so you can access multiple data points during a single visit.

The app displays the current temperature and relative humidity readings, with the low, average, and high over the last two weeks shown in a smaller font. You can also export the data via email to analyze the data over time. As I said, the app gets the job done.


That was the end of the good readings. The temperature readings were great: 50’s and 60’s during the day and as low as mid-40’s overnight. I suspect the cluster gets a bit tighter as the weather gets colder, and with a full medium of honey the sensor is further from the cluster and thus has a lower reading at night. During the warmth of the day the bees spread out more and the top of the hive heats up.

BroodMinder App

Late night readings from Mars showing a rather high relative humidity.

The relative humidity was another story. As you may recall, I assumed a screen on the bottom would vent the moisture well enough; and added insulation on top to ensure that any condensation that does occur would be on the walls and away from the bees.

At 7 pm that first evening the relative humidity (RH) reading was 92%, the same at 8 pm, and then at 10 pm it dropped to 85% RH. The next morning at 7 am it was down to 73% RH. I couldn’t find a lot of commentary online about what the humidity should be in a beehive, but this seemed high to me. A couple references indicated that in the summer the bees maintain a humidity in the low 70’s (I can’t seem to find these now, so no links to share for this).

My guess at the time was that as the temperature cooled and the bees formed a cluster, the drop in temperature (which raises RH levels) and the warming of the cluster (which raises moisture levels via respiration) caused condensation in the hive (hopefully on the walls, of course!). Water will condense at 100% humidity, so the high 90’s likely indicates that water was already forming somewhere at the top of the hive. The other possibility, of course, is that the reading was wrong, but I didn’t consider this at the time.

Not wanting to rely on a single data point, I checked the readings the following night. Once again the humidity was in the high 90’s and the reading at 10:30 pm is shown in the image: 98% RH. I was unsure what to do until I did some research on humidity in buildings. These sites mentioned that relative humidity over 80% tends to promote the growth of mold and mildew.


Added Ventilation

A small shim for ventilation at the top of Mars. The shim sits below the inner cover, and you can see the insulating board on top. The small tab from the BroodMinder device is also visible.

I really wasn’t interested in having mold and mildew in my hives, so it seemed time for some ventilation. Adding an opening at the top of a hive releases moisture; it also releases heat, which is why I was reluctant to add this. I had already purchased two shims with ventilation in mind. My inexperience made me worry about the consequences: would the bees get cold, would robbing bees find their way to the hive, or would wasps or other insects get inside the hive? So I had done nothing with them.

In fact, Fedor Lazutin talks about this trade-off in his book Keeping Bees With A Smile. He says very little air exchange is required for respiration, as sufficient oxygen transfer occurs even with a small bottom opening. Removing moisture requires either ventilation or water-absorbing material such as the decaying wood and leaves found at the base of natural bee hollows. Since the Russian winters are so miserably cold, Lazutin opts for placing absorbing material inside and at the base of his hives. He claims this works quite well, though he does mention that he cleans off the interior walls of his hives in the spring. In his scheme, the moisture is absorbed and more heat can be retained by avoiding top ventilation.

BroodMinder App

The readings a couple days after adding shims to both hives.

For myself, Tuesday morning I added a shim to each hive. My second BroodMinder arrived on Monday, so I added the new device and a shim to Jupiter as well.

Worked intervened here, as I had to travel to Michigan for the next couple days. I arrived home Thursday evening anxious to check the readings. After some time with the family, I visited the hives around 10 pm.

I was a little surprised to find that Jupiter had readings of 58 F and 85% RH, while Mars read 59 F and 92% RH. Go figure. Too late and too tired to do anything about it, I went to bed. I’m writing this Friday evening and the readings in both hives have been 100% for a few hours. Remember this is after adding ventilation, so either the hive is still damp at the top or the readings are incorrect.

Next Steps

As I mentioned, we are expecting a warm weekend: the forecast now calls for temperatures near 70 F (21 C) as I post this Saturday morning. I’m reluctant to open up the hives yet again, though will make sure the bees are flying and check the bottom boards for mites and moisture.

I sent a note to BroodMinder to see if they have any thoughts. There was also a poster on beesource.com that reported some problems with some of the moisture sensors. I am going to assume the hives are okay, perhaps they were okay all along and the BroodMinder has been misreading the humidity. Knowing the temperature is still useful, so will keep them in the hive and see how both the sensors and the bees behave in the coming months. Stay tuned.

Our title is a play on the song Baby It’s Cold Outside, written by Frank Loesser in 1944. The song was reportedly written and sung as a duet by Loesser and his wife during evenings with friends. Later it was recorded as part of the movie Neptune’s Daughter in 1949, when the song was seen as taking a liberal stance for women since the guest decided to stay despite what others might think. In more recent years the song is seen less favorably due to the man’s insistence that the woman stay despite her repeated refusals. I’m not sure it is fair to apply today’s standards to a 70-year-old song, and a recent article challenges the negative commentary about this song.

Now that we’re due for a few days of warm weather, the title doesn’t seem so appropriate. Perhaps I should use “Hey-bee, it will be cold outside again soon.” The perils of writing a post over multiple days of changing temperatures, I suppose. Stay warm out there.

5 thoughts on “Hey-bee it’s cold outside

  1. Fascinating post! I hope you’ll keep us updated with developments

    Lazutin’s comments on where to place moisture absorbing materials are interesting, but I wonder if the placement near the bottom works just as well in a vertical hive as in a horizontal one. Maybe they do since tree trunks are vertical.

    Have you read Warre’s book? His quilt is at the top, since he says it helps absorb moisture as it rises.

    I wonder what would happen if you added a quilt both on top and on the bottom. Overkill?

    Liked by 1 person

  2. Lazutin seemed to think it would work well top or bottom, perhaps he was looking to simulate the big old growth Russian forests by placing it beneath a screen on the bottom. My discussion of quilt boxes place them on top to allow the moisture to rise up through the hive. I suspect top and bottom quilts would work fine, though would this create too much open space for a draft or other heat escape. Not such a worry in Virginia, perhaps more so in your area.

    Haven’t read Warre’s book yet, I’ll have to add it my growing list.


  3. “This weekend we’re expecting temperatures near 70 (21 C)” – that would be a nice summer’s day in London! With your kind of temperatures my worry would be whether the bees have enough food – though perhaps there are actually flowers providing nectar if it’s so warm?

    This info on the Coloss site (a non-profit research association of scientists) says “Relative humidity within honey bee colonies (among frames and not within capped brood cells) is typically between 50 and 80% (Human et al., 2006; V. Dietemann, pers. comm.), and when given a choice between a range of relative humidities (i.e. 24, 40, 55, 75, and 90%), honey bees showed a preference for 75% (Ellis et al., 2008).” http://www.coloss.org/beebook/I/invitro/6/3/1

    As always different opinions can be found in beekeeping and Arnia’s site says “During the brood rearing period median levels of humidity in the nest of a healthy strong colony is between 50% and 60%. It is rarely found to be below 40% and above 80%” – http://www.arnia.co.uk/hive-humidity/ It mentions that humidity fluctuates more when the colony is broodless, but with your temperatures I would assume the queen is still laying. Apparently relative humidity in brood areas is significantly higher than the hive as a whole. We’re having highs of about 10-14 C in the daytime here now and I suspect our queens may be laying a small amount still.

    The data is interesting but I wonder if it’s making you worry too much. My experience has been that ventilation at the bottom and insulation at the top seems to work well, in combination with plenty of food and regular anti-varroa treatments/husbandry techniques during the year. But your local weather conditions are obviously much warmer – what do beekeepers local to you do?

    Liked by 1 person

    • As a first year beekeeper, I feel it is my duty to worry and fuss overly much – I seem to have that down. The local beekeeper practices seem to vary, I think it is warm enough here you can get away with most configurations. Some leave the screens on and a small bottom opening, others do a top and bottom vent. So I never had a consensus to follow and have been trying what made sense.

      There was an update from BroodMinder this afternoon that some units are erroneously reading 100%, so that is likely part of my problem (bad data). When I added the devices to the hive I did peek at the stores and there seems to be plenty for now. With the shim on I may add a candy board in January, but I do think they are okay for now. It is warm but we don’t seem to have any flowers or nectar about

      Thank you for the references and thoughts. I recall you mentioned the Coloss site before and I just forgot about it. I’ll have to give it a closer read, thanks again.

      Liked by 1 person

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s