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Oxygen Not Included Wiki
This article has not been revised for the current version (U40-494396). It was last updated for LU-356355. It may contain inaccuracies.
This article has not been revised for the current version (U40-494396). It was last updated for LU-356355. It may contain inaccuracies.

Temperature management is one of the key challenges of the game. Your Duplicants, your plants and your items will suffer and break if their temperature is too high or too low. The environment can get warmer through items that produce heat, creeps through walls and resources, even your Duplicants produce and spread some heat by mere existence. Similarly Chilliness can spread by air exchange or heat spreading towards colder regions. Controlling the environment is one of the key challenges in this game.

Formally, Heat is the amount of energy transferred to equalise thermal energy of two bodies. The game uses DTU per second to display heat output, it is equivalent to Joule per second or watt. Although it should not be confused with electric watt, since the game has no friction heat or electric heating in the general sense. Conservation of heat energy tend to vary depending on specific buildings.

It is too cold[]

This problem is the easiest to handle. Many game items, your Duplicants, and certain special features of your colony environment produce heat.

Heat sources[]

  • Space Heaters produces 18 kDTU/s heat at 120 W (150 DTU/s per watt), but it is generally not worth using, as its only other effect is meager 10 decor
  • Liquid Tepidizers produces 4064 kDTU/s at 960 W (~4200 DTU/s per watt). While it is slower, it is way more power-efficient and can be used as a core of a central heating system.
  • Charged Batteries and Jumbo Batteries produce 1.25 kDTU/s of heat when charged. They're small, short, clean and useful in other ways and so a good way to provide extra heat.
  • Power Transformers produces 1 kDTU/s of heat.
  • Ceiling Lamps produces 0.5 kDTU/s of heat at 10 W (50 DTU/s per watt), but it fits right above Sculpting Block.
  • Oxygen Diffusers produces 1.5 kDTU/s of heat at 120 W (12.5 DTU/s per watt).
  • Coal Generators produces 9 kDTU/s of heat while producing 600 W (15 DTU/s per watt) , but utilising it can be tricky, due to large amount of Carbon Dioxide in exhaust.
  • Cool Steam Vents outputs steam at 110 °C. It can be cooled down into 90 degree Water, which then can be piped around the colony, for example to Shower (Duplicants won't mind near-boiling shower). Heat will then radiate from the pipes.
  • Nearby Biomes can provide large quantity of heat (or cold). Biomes do not keep their own temperature after map generation, so this is a temporary source.

It is too warm[]

Buildings' output temperatures
Output temperatures Buildings
Input temperature
Fully consumes input
Fixed 20 Plants and Critter produced items based on Genetic Ooze.
Input Desalinator
40+ Molecular Forge (???)
70+ Electrolyzer
80 Kiln
90+ Oil Well
50+ Fertilizer Synthesizer
73.4+ Ethanol Distiller
75+ Polymer Press
~1750 Glass Forge
Varies by metal/coolant Metal Refinery
Unknown and/or irrelevant

This is the tricky bit. There are five straightforward ways to destroy heat:

  • Steam Turbine will convert hot steam above 125 °C into electricity, while cooling the steam into 95 °C water.
  • Ice-E Fan occupies a duplicant and uses up ice. It cools the gas at 32 kDTU/s.
  • Ice Maker, which deletes 20% of the heat in the water it cools (and releases the rest into its surroundings), and further reheating of ice will consume some more heat.
  • Wheezewort works rather slowly in most gases and natural setups and can not be mass-produced, but does not use any power. Its cooling is equivalent to 12 kDTU/s in the best circumstances.
  • Anti Entropy Thermo-Nullifier is able to provide around 80 kDTU/s of cooling by consuming hydrogen.

Avoiding heat[]

In early game, it's better to move the heat to where it won't cause trouble than to try to truly destroy it.

  • Dump excess heat in cold biome. Acquire cold gases and cold water from cold biomes.
  • Plant irrigation is one of the worst places to misplace extra heat - do not use hot water to irrigate cold-loving plants (Bristle Blossom). If you have no choice, use valves to avoid storing excess hot water in farms (water being consumed does not heat the plant up, standing water does), use insulated pipes in the sections that need to stay cool, and pre-cool the water by winding pipes carrying it through cool areas
  • Avoid creating machines like Polymer Press or Metal Refinery, but Ranch critters instead. This is really important in early game, when you do not have much time or resources to create proper rooms, gadgets and other things you may need to avoid spread heat. Most materials can be "fabricated" by critters.
  • Use Igneous Rock pipes for hot fluids/gas in early-mid game. At late game use Ceramic and insulation when managing really hot fluids/gases.

THC differences[]

In the Launch Update, the majority of buildings were given temperature floors for their outputs, instead of a fixed temperature or one set by the temperature of the building itself. This significantly complicated heat deletion tricks, and made them more reliant on inadequacies in mass conservation, which happen to also erase the carried heat energy alongside the mass.

The buildings that allow for that can be found by differences in Total Heat Capacity of their inputs and outputs.

The heat energy erasure happens in cases where inputs' THC is above the outputs' THC, and tends to get more potent with higher temperatures. It incentivize running some machinery with inputs as hot as possible to leech heat from other places, however the extra-hot output materials still need to be cooled down themselves.

In other cases, the THC difference in materials makes the machinery inherently heat multiplying, this effect will increases the further the inputs' temperatures deviate from the floors (in either direction, but stronger in up). Penalizing running them outside the optimal temperature.

It also important to notice that some heat deletion is necessary for the long-term survival of your colony, since the game constantly adds more heat, one way or another.

Specific Heat Capacity[]

This property quantifies how much an object's temperature changes if one adds or removes an amount of heat energy, per unit mass. Its unit is . Objects with larger specific heat capacity can hold more heat (or coldness—the lack of heat). Therefore, objects that are more massive or are hotter hold more heat than objects that are less massive or are colder.

Sometimes people talk about the "heat capacity" or "total heat capacity" of an object. An object's "heat capacity" is the specific heat capacity times the mass of the object. Conversely, the "specific heat capacity" of an object is equal to its total heat capacity divided by its mass. Note that buildings inherently have 1/5 the total heat capacity from what the straightforward formula would suggest.

Many calculations also talk about "total heat" or "heat energy". This is simply the total heat capacity multiplied by the temperature. However, there is a catch: This quantity depends on the units you use for temperature! The most physically "proper" way would be to use Kelvin, such that absolute zero would mean zero total heat. But if we measured this way, it would result in some buildings being incredibly good at heat deletion, and others staggeringly heat-generating. Instead, by convention we use Celsius, with a zero point that is much closer to temperatures that dupes actually experience.

How much heat transfer is required ...[]

... to cool down one Tile of Water with 80 °C to 20 °C in a Cycle? A tile full of Water contains 1 tonne (1,000,000 grams) of Water. The Temperature difference is 60 °C, the cycle is 600 seconds and the Specific Heat Capacity of Water is:

Thermal Conductivity[]

This property defines how quickly heat can be exchanged between two objects (where walls, resources, gas, liquids, plants and items all are objects). A lower value means heat is transferred slower, a higher value means heat is transferred faster. The rate at which two objects exchange heat is defined by the lower thermal conductivity value of both objects (except for non-insulated pipes and buildings). For detailed formula see Thermal Conductivity.

Its unit is . In this game, a Tile is considered to be one meter high and wide.

The larger the temperature difference between two objects, the more quickly heat will be transferred between them, but the longer overall it will take for them to equilibrate (come to the same temperature). Because of this, materials with high thermal conductivities are useful in situations where one wants to transfer (or conduct) heat quickly, and materials with low thermal conductivities are useful in situations where you want to prevent the transfer of heat via insulation.

For more information on how Energy and Wattage (Power) are related, read the Power guide. Here is a nice video explaining it.

Choosing Coolant[]

Thermal Conductivity, counterintuitively, is the least important parameter, it has to be higher than other recipients to collect heat, but only as much, since the system will be inevitably bottlenecked by the material with the lowest Thermal Conductivity.

Mass and Specific Heat Capacity, on the other hand are extremely important, since they will define the maximum size of "heat packet" that can be transferred. For example Super Coolant limited to 1 kg will perform almost as good as packets of 20 kg Thermium, despite their vast difference in conductivity. This is further capped by contact zone / radiator size, which might not be enough to fill or free the full packet.

Temperature range is a matter of convenience and/or limiting factor. Petroleum and Crude have great temperature range, but are the poorer mediums, that are competitive due to ability to maintain mass concentration. Hydrogen has good SHC, but mostly exist as a low-mass gas which limits its throughput. Water has good mass and SHC, but limited by its narrow state transition temperatures.

Heat Movement Directions[]

Assuming the same materials, on solids and all materials heat disperses evenly, however, gases such as oxygen will rise if they are hot, the oxygen will be sorted by its heat where the hottest is at the top, water is affected the same.