Heat from below, spread across the footprint
A PTC ceramic element in the Bottom Treatment Frame heats through a diffuser board that spreads output across the full width of the hive rather than concentrating it at one point.
How it works
Precision heat.
Zero chemicals. Tested in the field.
Varroa mites die at temperatures honey bees survive. ThermaHive holds the brood nest inside that window for the length of a treatment, without opening the hive, pulling frames, or adding a single chemical.
We ran that protocol across a full research apiary in Maryland through 2026, logging every treatment to the second, alongside independent testers in three states. See what the season showed.
ThermaHive setup
How ThermaHive fits your hive
ThermaHive goes above and below the boxes you already own. Your frames, boxes and bees stay exactly where they are. Select any part to see it up close.
ThermaHive parts
Your existing equipment
ThermaHive
Your hive
ThermaHive
Tap a number or a part name to see photos.
How heat moves
Heater Insert
Diffuser
Your hive boxes
Top Box fans
Why heat works
A window only one species survives
Held at 108 to 112°F (42 to 44°C), heat kills Varroa while bees and brood come through it fine. A mite cannot evolve its way around that, because you cannot build resistance to physics.
The idea is simple. Holding it is the hard part: the window is narrow, the colony fights the heat by fanning and evaporating moisture, and mites under cappings only die if the heat actually reaches them. That means regulating to the brood nest itself, not the air around it.
Airflow that works against the colony's cooling
Two 120 mm fans, one per half of the hive, move warm air up through the frames. Output scales with the gap to setpoint, so the system pushes through the colony's fanning without overshooting once it arrives.
Measurement from inside the cluster
A wireless sensor sits between frames at bee space and reports every two seconds. Every heating decision is made against what the brood nest is experiencing, not the equipment.
Field test photo.
Controller, pre-mounted to the top box.
Wireless sensor seated at bee space between frames.
The hardest part
Holding the window
Anyone can make a hive warm. Holding one temperature inside a living, thermoregulating colony for three hours is a control problem, and it is where most of our engineering has gone.
Measurement at the source
V1 taught us this the expensive way: a sensor in the controller enclosure reads the enclosure, and in our logs it ran several degrees off the colony. Control from that and the heater throttles early, so the treatment never reaches dose.
V2 puts an SHT31-DIS sensor between two frames at bee space instead. No drilling, no cable, nothing to reseat, and it stays put through inspections.
ThermaHive V1 vs V2: what changed (PDF)
What that control looks like in the log
Our best recorded hold, July 23, 2026: three hours at a 112°F (44°C) setpoint averaged 112.03°F (44.5°C), standard deviation 0.75°F (0.4°C), with 99.6% of the hold inside ±2°F (±1.1°C).
The fullest, most populous boxes run coolest and take longest to get there, so we log the hold mean and in-band percentage of every treatment.
Control that anticipates rather than reacts
Fan output steps up as the gap to target widens, with a boost during warm-up to get through the colony's clustering and fanning. Once at target, corrections stay deliberately conservative, because over-correcting after an overshoot just restarts the oscillation.
Verification, not assumption
Every session logs to the SD card, and the in-hive sensors report every two seconds, so you can follow a treatment as it runs in the BroodMinder app. You are not told a treatment happened. You are shown the curve it held.
Interactive model
How the hive heats
Watch a treatment from the inside. Air heated at the base spreads through the diffuser board, rises between the frames of both brood boxes, and leaves through the top fans and vent holes. Switch to scenario 02 to see the fans balance a hive with one side chilled by wind.
Loading the simulation…
An illustrative model, not calibrated to our test data, with timing compressed. Toggle °F and °C, change the outside air and target temperature, or switch between the front and side views.
In development
Smart fan tuning: learning each hive
Heat does not spread evenly through a colony: the bottom plate runs hot, the corners run cold, and mites survive in the cold pockets. Fans even that out, but the right speed depends on the hive, so we are building a controller that learns it.
Safety sits outside anything the system learns. If a hive gets too hot the heater shuts off, and no amount of learning can override that.
The thermal model shows why the fans matter. Heat enters at the base, and when one side of the box lags, more airflow on that side brings it level.
Adjusting in real time
During a treatment the controller checks the hive every few seconds and nudges fan speed based on how even the temperature is. That helps immediately, even on a hive it has never seen, but it is reactive.
Learning through experience
It also tries a setting for a whole treatment and keeps it only if the result clearly beats its best so far. Weaker results are discarded, so one off day cannot erase a setting that works.
Learning never overrides safety
Hard temperature limits, a brood-safety cutoff and a monitor that reverts to the trusted baseline at the first sign of trouble all run underneath, so an experiment in fan tuning can never put a hive at risk.
This system is still in development and is not yet part of a shipping unit. We will share progress as it moves through our own testing.
Start to finish
Step by step
Two steps happen once. The rest is treatment day, and you are not present for most of it.
1
Install the Bottom Treatment Frame (once)
It replaces your screened bottom board, or sits under the one you have. It stays on the hive year round, and with the Blank Insert in place it works as a standard screened bottom board.
2
Place the wireless sensors (once)
Two SHT31-DIS sensors clip into Hex Saddle mounts and drop between brood frames at bee space, no drilling. They stay put through inspections and run on CR2032 coin cells that last around 248 days. See the sensors.
3
Swap in the Heater Insert
Blank Insert out, Heater Insert in, held by magnets. On treatment day this is the only structural change to the hive.
4
Set the top box on and power up
The controller comes pre-mounted. Inner cover off, top box on, telescoping cover back over it, then the cord into the Heater Insert and power from an outlet or a solar battery. Your setup is saved, so later treatments skip the menu.
5
Start it, then walk away
Set temperature and duration. We recommend 112°F (44°C) for three hours, so that every part of the hive spends at least two hours at 108°F (42°C) or above. Heating starts at once, but the treatment clock only begins when the brood nest reaches setpoint: budget 30 to 60 minutes of preheat, then two to three hours of hold. The hive stays closed, and you do not need to be there for any of it.
6
Cool down, then read the record
The heater shuts off at the end of the hold, and the fans keep running if Ventilation Mode is on. Every session writes to the SD card: temperature, humidity, phase, settings and safety events, all timestamped, opening in Excel or Google Sheets.
Set up in step 4
Additional modes
A treatment is not the only thing the controller runs. All four are optional.
Heater On/Off
Heats when the hive drops below your ideal temperature and stops once it gets there. For winter and early-spring cold snaps.
Ventilation Mode
Runs the fans outside a treatment, to hold normal hive conditions or to cool the hive once a treatment ends.
Ventilation Auto Mode
Fans start when hive temperature rises above your ideal, 95°F (35°C) by default and adjustable either way.
MCP Ventilation Mode
Set an ideal temperature plus temperature and humidity thresholds, and the system works to hold those conditions.
Heater On/Off option.
Ventilation mode menu: Off, Auto, or MCP.
Selecting your ideal hive temperature.
What one treatment can and cannot do
The brood cycle is the schedule
One treatment is a dose, not a cure. Time your rounds to the brood cycle, and read every wash with the brood in mind.
Most of a colony's mites are sealed inside capped brood, where contact treatments cannot reach them. Heat can, and that is the main reason we use it.
But a mite wash only counts the mites riding on adult bees. It cannot show what happened under the cappings until that brood emerges, so a wash is a snapshot of one compartment of the mite population, not a verdict on the treatment before it.
What this means for you:
- Wash before, then five to seven days after. The before count is optional, but it is what turns the after count into an answer.
- Treat twice per brood cycle, 7 to 10 days apart. That is the standard regimen. A small colony may need only one treatment per cycle and a big one three, and as mite numbers fall you should be able to drop to one per cycle. How often to treat.
- Note what the brood is doing when you sample. A mid-emergence count and a brood-break count are not comparable numbers.
- A rise should not be the norm. If a wash comes back above your seasonal threshold, treat again. Why a count sometimes rises.
Frame of capped and emerging brood mid-cycle.
ThermaHive regulates to the brood boxes
Heat rises into a super, but a super runs several degrees cooler than the brood nest the controller holds at setpoint, so mites up there get a weaker dose. Keep a queen excluder in place, or treat with the super configured as a brood box.
Built-in protection
Multiple independent layers
Four layers protect a running treatment, and they do not depend on each other. Every failure mode ends with the heater off.
1
Firmware ceiling
Any sensor above the configured maximum cuts the heater immediately and logs the event. It is a limit, not a setting: treatments run at 108 to 112°F (42 to 44°C).
2
Fault blocking
Invalid or missing sensor data blocks heating until reliable readings return. The system refuses to treat blind.
3
Factory protection at the heater
The heater carries its own 100°C cutout and 112°C thermal fuse, so it is protected whether or not the controller is alive. Designed to meet IEC 60335-1.
4
Hardware watchdog
If the processor stalls, the watchdog resets the controller and opening the heater relay is its first action on restart.
Also built in
- Conservative sensor logic. The system controls from the most conservative valid reading, so an optimistic one cannot mask a hot spot.
- Independent heater interlock. Ventilation and cooling stay available even when the heater is disabled.
- Soft-start ramping. Temperature climbs gradually rather than spiking, which spares brood and wax.
- Power recovery. After an outage the unit restarts into a safe state. Our field units came back from storm cuts on their own.
- IP65-equivalent enclosure. Mounted continuously through storms and a Maryland summer.
- Entrance reducer recommended. It keeps warm air in so the fans can spread it evenly across the box.
2026 research season
What the 2026 season showed
A full research apiary in West River, Maryland, with untreated and chemically treated control groups, under Allan Storm, Master Beekeeper and Maryland State Bee Inspector. Independent testers in three states ran their own units on their own hives.
51% average reduction per treatment measured on 49 paired mite washes on 16 colonies (95% CI 31 to 65%). No treated colony was lost, against one of six in the chemical control group. See the full 2026 results.
Control precision
Our best recorded hold averaged 112.03°F (44.5°C) against a 112°F (44°C) setpoint, with 99.6% of three hours inside ±2°F (±1.1°C). Delivery varies with the colony.
Independent testers
North Carolina logged a 71% average reduction across 23 treatments on 10 hives (p = 0.00005), on their hives and their counts. Full tester results.
More than one setting works
We did best at the top of the range, 112°F (44°C) for three hours. Testers did just as well at the bottom, 109°F (43°C) for a little over two. Find yours inside the range rather than assuming ours.
Colony and queen safety
Colonies with the longest treatment histories kept healthy brood nests, in one case twelve frames of capped brood. Mortality ran ten to twenty bees per session, mostly drones. No queen was lost, and a capped queen cell treated mid-cycle emerged and began laying.
Research apiary in West River, Maryland.
Mites at the bottom of a soapy-water wash cup.
Queen on a frame during a queen-safety inspection.
The full record is published
Colony-by-colony mite trajectories, the independent tester charts, outside verification from the National Honey Bee Survey, and the fourteen washes that came back higher. Read the 2026 field results.
Ready to treat chemical-free?
Pre-order the ThermaHive V2 Complete Kit and put this season's field results to work on your own hives, backed by a lifetime warranty.
Year-round value
One device, every season
ThermaHive is not a two-weekends-a-year tool. It stays on the hive.
Spring
Gentle warming and airflow help weak colonies through cold snaps and speed early buildup. Establish your mite baseline and start your first treatment sequence before the population climbs.
Summer
Precision heat through the peak brood period, with no chemicals, no frame removal, and no harvest restriction. Ventilation Mode moves air on the hottest days without running a full cycle.
Fall
A second treatment sequence clears mites before winter bees are raised, the highest-leverage moment in the mite calendar.
Winter
Passive monitoring logs hive temperature and humidity so you know the colony is alive without cracking the lid on a cold day.
Beyond one hive
One heater. Many hives.
The expensive part of a thermal system is the controller and the heating element. The part that has to live on every hive is just a bottom board, so we split them.
Every hive gets a Bottom Treatment Frame, a fraction of the cost of a kit, which doubles as a standard screened bottom board the rest of the year. On treatment day you carry the Heater Insert and top box to whichever hive needs them. Your per-hive cost to expand is the frame, not another system, and one controller pairs up to 50 sensors.
- No brood boxes get moved
- No frames get pulled
- No chemicals get rotated, tracked, or timed against a harvest window
Treatment units draw real power. In our apiary three units is the safe maximum on one household circuit; a fourth blew a fuse. Spread them across separate circuits.
V2 Heater Insert. It pulls out in seconds to move to the next hive.
Bottom Treatment Frame, showing the magnetic lock.
The V2 Complete Kit: Top Box and Controller above, Bottom Treatment Frame and Heater Insert below.
Common questions
Frequently Asked Questions
Treatment settings, colony safety, what heat does to your honey, and how the system scales across an apiary.
What temperature and duration should I use?
The working range, why there is no single right answer inside it, and how to find yours.
Does the heat affect raw honey enzymes?
What the EU and Codex thresholds actually require, measured against our own logged exposure data.
How does this work across multiple hives?
The full swap-and-treat cycle, step by step, and what stays on each hive year round.
Want the full details?
Download the V2 spec sheet for complete hardware specifications, or pre-order the V2 Complete Kit and treat your first hive chemical-free.