1. VIVOSUN Fermentation Heat Belt
This is the industry standard for home brewers. It is a simple, plug-in strap that you wrap around your jar. It doesn't have a thermostat, but you control the temperature by sliding the belt up (less heat transfer) or down (more heat). It raised our 5L jar from 18°C to a perfect 25°C in about 4 hours and held it there.
Pros
- Encourages healthy convection
- Fits any size jar (adjustable band)
- Very energy efficient (low wattage)
Cons
- No off switch (must unplug)
- No precise temperature control
2. Inkbird ITC-308 Temperature Controller
If you are brewing Jun Tea (which is sensitive to high heat) or simply want perfection, you need this. It removes the guesswork. You set it to 24°C, and it handles the rest. It stops your brew from overheating on sunny days and freezing on cold nights. Essential for brewing in a garage or shed.
Pros
- Set-and-forget precision
- Prevents overheating (yeast stress)
- Digital readout of current temp
Cons
- Requires a separate heat mat
- More wires/clutter
3. Generic Seedling Propagator Mat
You can find these for £10-£12. They are waterproof and durable. While they aren't shaped for jars, they are flexible enough to wrap around a standard 3L Kilner jar. They tend to run cooler than dedicated brew belts, raising the temp by only about 5°C-8°C above ambient, which is usually enough for a UK kitchen.
Pros
- Cheapest option available
- Waterproof (spill safe)
- Multi-use (good for seedlings too)
Cons
- Awkward to secure around round jars
- Can overheat yeast if placed underneath
4. Kenley Fermentation Carboy Heater
If you have upgraded to a massive 8L dispenser jar, a little strip belt won't cut it. The Kenley wrap covers a much larger surface area, ensuring the entire thermal mass of the liquid is heated evenly. It comes with a simple dial thermostat (High/Low/Off), giving you basic control without needing an external controller.
Pros
- Powerful enough for large vessels
- Built-in thermostat dial
- Even heat distribution
Cons
- Too big for small 1L jars
- More expensive
5. Reflectix Insulation Wrap (DIY)
This isn't a heater, but we recommend it as an add-on. If you are using a heat belt, 50% of that heat is lost to the room air. Wrapping a layer of Reflectix insulation over your heat belt forces that energy into the jar. It makes your heater twice as efficient and ensures stable temps even if the room drops to freezing.
Pros
- Increases heater efficiency
- Protects SCOBY from UV light
- Very cheap (buy a roll)
Cons
- Ugly aesthetic (looks like a spaceship)
- Hides the brew (can't see mold growing)
Warning: The Airing Cupboard Trap
Many UK guides suggest putting your jar in the airing cupboard (hot water tank closet). Don't do it.
1. It is often dusty (mold spores).
2. It is dark (hard to monitor).
3. The temperature fluctuates wildly when the boiler cycles on/off.
A consistent £15 heat belt is cheaper than ruining 3 batches of tea.
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