Why is fermentation temperature control important?

Yeast produces different flavours at different temperatures. Too warm and you get fusel alcohols, excessive esters, and harsh flavours. Too cold and fermentation stalls or takes excessively long. Controlling temperature within ±1°C of your target produces the best and most consistent results.

What is the cheapest way to control fermentation temperature?

A "swamp cooler" — place the fermenter in a tub of water with frozen bottles, rotating them as they thaw. For heating, a brew belt or aquarium heater in the water bath works well. For around £25-40, an Inkbird ITC-308 controller with a second-hand fridge gives excellent temperature control.

Does fermentation produce heat?

Yes. Active fermentation is exothermic and can raise beer temperature 3-8°C above ambient during the most active phase (typically days 2-4). This is why cooling is often needed even when ambient temperature seems appropriate.

What temperature controller should I use?

The Inkbird ITC-308 is the most popular choice for homebrewers in the UK. It has both heating and cooling outlets, a probe that goes into the beer or tapes to the fermenter, and costs around £25-35. It can control a fridge for cooling and a heat pad for heating.

How much heat does fermentation generate?

Active fermentation can raise the beer temperature 3-8°C above ambient during peak activity (days 2-4). This exothermic heat is why cooling is often needed even when the room temperature seems fine. The temperature spike can produce off-flavours if not controlled.

BrewCalcs

Temperature Control Calculator

Calculate heating or cooling needs for fermentation temperature control.

Batch Size

Ambient Temperature

Room / environment temperature

Target Fermentation Temperature

Fermenter Type

Control Method

How We Calculate This

Heat Transfer Calculation

The calculator estimates heat exchange through fermenter walls using: Q = U x A x ΔT, where U is the overall heat transfer coefficient (~5 W/m²/°C for typical fermenters), A is the fermenter surface area, and ΔT is the temperature difference.

Fermentation Exotherm

Active fermentation generates approximately 0.5 watts per litre of wort. This heat must be accounted for in cooling calculations — even if ambient temperature equals your target, you still need some cooling capacity during peak fermentation.

Frequently Asked Questions

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Last updated: 2025-02-20

All calculations are estimates. Always verify values and adjust based on your equipment and ingredients.