Temperature

Temperature management is an important part of a productive colony. Temperature mostly affects pawn mood, food and corpse spoilage, and plant growth. In some biomes outdoor temperature can reach deadly highs, lows, or both depending on the season - pawns must wear appropriate clothing to survive long periods of time outdoors. Temperature also plays a major role and is affected by many things in world generation. Extreme cold or heat can even kill animals, and extreme heat can cause and sustain fires.

Basics

Cold temperatures preserve food and corpses by slowing spoilage. Freezing temperatures preserve food and corpses indefinitely, but can also cause hypothermia in living things and eventually freeze them to death. Warm temperatures rot food and corpses, and extreme heat causes heatstroke which can also lead to death.

Outdoor temperature usually fluctuates slowly by day and season and is bounded by the climate of your biome. Be careful though, because unpredictable events like cold snap and volcanic winter can also change outdoor temperature unexpectedly.

Clothing modifies the temperatures that cause heatstroke or frostbite, as well as the various mood debuffs from uncomfortable temperatures. Colonist moods ignore clothing when sleeping, becoming unhappy in a mildly cold or hot bedroom. When faced with temperature extremes, colonists automatically search for and equip any suitable clothing they can find in storage.

All indoor rooms have their own temperature which can be seen by mousing over it. Indoor temperature can be managed through structures in the temperature menu. Keep in mind that heat transfers between rooms and also the outside through roofs, walls, and doors. Large temperature differences, open doors, open roofs, and long thin rooms can make temperature hard to regulate. Larger rooms have more thermal "mass", and their temperature changes more slowly than smaller rooms.

Temperature/heat transfer inside a room is instantaneous regardless of room size. This means long hallways can be used to transfer heat easily through a large base.

Double thick walls and intermediate rooms act as an insulator and slow heat transfer- try using a hallway or storage room to protect bedrooms and work rooms from temperature extremes. Any room that borders an outdoors area transfers more heat, and will usually be closer to outdoor temperature, even if the room borders solid rock.

Try not to build long thin hallways connecting with the outdoors, or leave large solid rock clusters inside your base. This will increase your surface area to outdoor temperature and make indoor temperature more difficult to manage. Cut off outside hallways using doors and mine rock until all traces of outdoor area are gone.

Managing Temperature

Temperature management is important for any colony, regardless of climate. It can be simply managed with a good power supply and the following structures.

Note: When adding coolers/heaters, it's important to know that a structure will always share the "outside" temperature until it is fully "indoors" (which usually means walls and/or doors). Adding coolers/heaters before this is fine, but they will not start to change the temperature until the area is defined as "indoors".

Cooler

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The cooler is primarily used to lower the temperature of a room. It has two states of power consumption: low and high. In its low state, the cooler produces no heat or cold but still requires 20 W. It can be used to lower the temperature of a room to a comfortable 20 °C (68 °F) (room temperature) in the summer or create a walk-in freezer for your food. In hot biomes such as desert or rainforest, having comfortable air conditioning is a necessity for any base.

Coolers are heat pumps that produce both a cold side and a hot side. The hot side is rarely useful and should be directed to an outdoor space to not inconvenience your colony.

A cooler is theoretically able to cool a single square by about 1800 kelvin [K]. But this is not a linear relation as a room always exchanges heat with adjacent rooms and/or the outside. Example: In a realistic setup, this means it can cool a room with 50 squares by an average of about 36 K per square. So a room with 50 squares and an outside temperature of 60 °C (140 °F) can be cooled down to comfortable 24 °C (75.2 °F) or something near that with a single cooler.

Freezer

A freezer is the most straightforward use of coolers for a starting colony. Building one is as simple as making a room and replacing some wall tiles with coolers. Direct the cold "blue" zone of the cooler inside the room and the hot "red" tile to an outdoor area. Select the cooler temperature settings and reduce their target temperature so that they continue running below 0 °C (32 °F). As the room cools down any food left inside will decay more slowly until it freezes. Frozen food will stay fresh indefinitely and incurs no other benefit or penalty when eaten.

If your freezer area is more than about 50 squares, and/or you are living in an area with a hot summer, you will want 2 coolers (and perhaps more, see "adding coolers", below). Put one at 32, and the other at 30. With double walls, this will let one cooler "idle" at 20 W of power in cooler weather while the other easily keeps things frozen, but be available to help when needed for warmer weather.

Also, put a battery (or three) nearby on a power switch, close enough to connect to your coolers (6 tiles), but kept off your power grid once charged, on standby. If you have a power problem, you can immediately click "reconnect" on your coolers, which will take power directly from the batter (no power conduit needed), keeping your freezer frosty until you can fix the power problem.

Freezer Tips

Building freezers that can tolerate extreme heat, due to the biome or heat waves, can be challenging. The type of material used to build the walls does not matter because they all have the same insulation values. However, increasing the walls from 1-thick to 2-thick dramatically improves the insulation, but thickness beyond 2-thick does not have a noticeable effect. Never block a cooler's intake or exhaust port or else it won't function.

Freezers lose a great deal of cooling through doors as pawns open them. This loss can be offset by having doors arranged in sequence, one after another, at points of egress, in an "airlock" like fashion. The loss can be examined by mousing over the sections of the airlock to see the temperature. Using doors rather than autodoors can help reduce the cooling lost, though this slows down colonists.

The hot end of the Cooler is useful for climates where the temperature rarely gets above 20 °C (68 °F) and almost never above 30 °C (86 °F). Instead of pointing the freezer's hot end outside, point it directly into your base. This will increase your energy efficiency and may save a few components on Heaters.

Adding coolers

There may come a moment when you realize "I don't have enough coolers for this area...". If the weather is cool, that's not a big problem, but it's more likely that the weather will be brutally hot when you realize this. And it's also likely that it's your freezer that's not at "freezing" (since colonists can tough it out). If you open a wall to put in an additional cooler, your freezer immediately rockets to "outside" temperatures - which is probably a dealbreaker, rotting all your frozen items. So here's what you do...

Decide where in the current wall you will put your new cooler, and build a door outside the wall there. Then [f]orbid the door, and deconstruct the wall; the door will act as a wall and maintain the area as "inside" (you don't need "side walls" to support the door). Then build your cooler (remembering the orientation, warm side "out"). Once the new cooler has been installed, immediately force the door open (to let the heat out) and then deconstruct it.

Passive cooler

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The passive cooler is a very low-tech option automatically unlocked for tribal starts. They operate at the same strength as a Cooler and will cool rooms to a very comfortable 15 °C (59 °F) for 5 days. It needs to be fueled when it runs out of fuel.

Passive coolers are a life saver in extremely hot climates as they can be quickly built, are immune to electrical events and are easily massed in a heat wave. Use passive coolers to keep your living spaces survivable and chill rooms surrounding a freezer to further protect the products inside.

Heater

The heater is used to raise the temperature of a room. It has two states of power consumption: low and high. In its low state, the heater produces no heat but still requires 18 W. It can be used to raise the temperature of a room to a likable 20 °C (68 °F) (room temperature) in the winter or create a walk-in heat trap for your foes. In any cold biome, such as the Tundra, the heater is a necessity for any base.

A heater (in theory) is able to heat a single square by about 1800 kelvin [K]. But this is not a linear relation as a room always exchanges heat with adjacent rooms and/or the outside. This heat conduction effect can be pretty noticeable in extremely cold or hot environments. Example: In a realistic setup, this means it can heat a room with 50 squares by an average of about 36 K per square. So a room with 50 squares and an outside temperature of -10 °C (14 °F) can be heated up to comfortable 26 °C (78.8 °F) or something near that with a single heater.

Campfire

Campfires are a quick and dirty solution to produce heat in a hurry. They require no energy, but are temporary structures and must be refreshed with wood every few days. Otherwise they produce the same amount of heat as an electrical heater.

They cannot raise the temperature to over 30 °C (86 °F).

Generators

Generators produce a non-negligible amount of heat for the room they occupy, especially when placed in numbers. If placed strategically you can reduce the number of heaters and coolers necessary to manage the temperature in your base.

It's also worth noting that generators will continue to produce heat (and burn fuel) during solar flare events. If your colony is in a very cold climate, this can be used to ensure that critical sections such as hydroponics or barns for sensitive animals don't lose all their heat in a power outage.

Vent

A vent allows transfer of temperature and gases from one room to another.

Vents can have any building in front of it, but no walls. Vents work best when connecting directly to a climate controlled room. Trying to chain vents across smaller rooms will lead to each successive room getting less effective climate control, and connecting to a hallway won't work well if the hallway is blocked with doors. A vent can be designated to be closed, an action carried out by colonists assigned to flicking.

Steam Geysers

A steam geyser will heat up a roofed room even when covered with a geothermal generator. They are extremely useful for staying warm in frozen climates but can overheat an indoors space in warmer biomes.

Fire Weapons

Weapons that generate fire such as Molotov cocktail and Incendiary launcher can be used to quickly generate heat inside your colony. Under normal conditions this is a bad idea because fires will quickly bring your base to intolerable temperatures. However in a bitter arctic climate with no wood and inadequate heaters, these weapons are your last defense against freezing to death. Draft your colonist and force them to open fire on an empty space, or burn spare corpses and rags to increase heat output.

Doors

Similar to double thick walls, double doors (not side-by-side, rather, both in the path of travel) improve insulation and reduce temperature equalization. A door can be left permanently open (mark the door to 'hold open' and have a pawn pass through) to help control temperature. Open doors allow temperature to more quickly equalize between rooms, or outdoors for exterior doors. Equalization through open doors is less potent than vents.

Solar Pinhole

Solar pinhole is a psycast that creates heat and light. It lasts five days. It is useful for emergency situations, such as power shortages during cold snaps.

Extreme Temperature Effects

A heat wave near the equator in a hot season (and equators have two of those) can top 60^oC / 140^oF, which is bad enough. But things can get much, much worse...

The maximum temperature is 1,000 °C (1,832 °F) and the minimum is -270 °C (-454 °F), very close to absolute zero. The minimum temperature is not encountered during normal unmodded gameplay, but fires in small enclosed spaces can reach the maximum temperature. The gear tab also shows aggregate stats about comfy temperatures.

There is an orange glow when hovering over very hot areas to help you identify them. In these areas, it is so hot that flammable objects will spontaneously catch fire, and pawns will be burnt by superheated air.

On pawns

Temperatures below a pawn's minimum comfortable temperature or above their maximum comfortable temperature will cause them discomfort with mood debuffs and in extreme cases can cause ailments and even death. A pawn will be happy within the range set by their minimum and maximum comfortable temperatures, and safe within 10°C of them. Beyond that, there is a risk of heatstroke or hypothermia. Insectoids do not suffer from hypothermia, and instead get hypothermic slowdown. At very extreme temperatures^{How extreme?}, there is the risk of spontaneous burns and frostbite.

Note that human pawns will also get a mood debuff for "Slept in the Cold/Heat" any time they sleep in an area outside their natural, i.e. before clothing, range of 16 °C (60.8 °F) to 26 °C (78.8 °F) - this occurs regardless of the apparel they wear.

The simple cure for any afflicted colonist is to return them to a normal temperature environment. This process can be sped up by forcing the colonist into the opposite extreme, such as putting heatstroke victims in a freezer to cool off.

Ailments include:

Heatstroke - caused by prolonged exposure to heat.
Burns - caused by exposure to extreme heat or contact with fire.
Hypothermia - caused by prolonged exposure to cold.
Frostbite - injury to extremities caused by prolonged exposure to cold.

On objects

Objects such as wooden structures and furniture will ignite once they reach a high enough temperature, depending on their material's flammability. All stone types and uranium have their flammability set to 0% and therefore objects made from them will not ignite or burn in any temperature. Steel, plasteel, silver, gold and jade are flammable as materials, but not as items.

Extreme cold has no negative effect on objects; most food and plant matter items spoil depending on temperature, and become refrigerated at temperatures below 10 °C (50 °F), slowing down the spoiling process. When temperature reaches freezing (0 °C (32 °F)), they become frozen and completely stop spoiling.

Fertilized eggs can become "ruined by temperature" in either moderately hot or cold environments. They are still usable as food, however no animal will hatch from them.

Temperature Thresholds

It is important to know where Temperature might become an issue. Often multiple aspects have to be considered with Temperature: Pawn Limits, Sleeping Pawn Limits (which exclude clothing values), Workbench Limits, Plant Limits.

For example, the highest and lowest temperature pawns can survive is way above and below the temperature for plant growth and the temperature range of most workbenches. In extreme heat, even the spontaneous Combustion of Building Material becomes an issue.

Temperature	Effects
1,000 °C (1,832 °F)	Maximum value
~235 °C (455 °F)	Items spontaneously catch fire
50 °C (122 °F)	Animals max temperature
44 °C (111.2 °F)	Plant growth slowed
30 °C (86 °F)	Campfire max temperature
26 °C (78.8 °F)	Default human upper limit
21 °C (69.8 °F)	Heater and Cooler default target
16 °C (60.8 °F)	Default human lower limit
15 °C (59 °F)	Passive cooler min temperature
10 °C (50 °F)	Below this value plant growth and food spoiling slowed. Food spoiling is multiplied by a factor equal to 10 divided by the temperature in Celsius
9 °C (48.2 °F)	Food spoiling rate divided by a factor of 1.11.
8 °C (46.4 °F)	Food spoiling rate divided by a factor of 1.25.
7 °C (44.6 °F)	Food spoiling rate divided by a factor of 1.43.
6 °C (42.8 °F)	Food spoiling rate divided by a factor of 1.66.
5 °C (41 °F)	Food spoiling rate divided by a factor of 2. Bad temperature bench modifier
4 °C (39.2 °F)	Food spoiling rate divided by a factor of 2.5.
3 °C (37.4 °F)	Food spoiling rate divided by a factor of 3.33.
2 °C (35.6 °F)	Food spoiling rate divided by a factor of 5.
1 °C (33.8 °F)	Food spoiling rate divided by a factor of 10.
0 °C (32 °F)	Plant growth and food spoiling stopped.
-10 °C (14 °F)	Most plants die.
-273 °C (-459.4 °F)	Minimum value.

Room Temperature Mechanics

Temperature mechanics

Equalisation calculations happens once every 120 game ticks.

All internal calculations are done in celsius. Fahrenheit is simply a different way to display the same absolute value.

Temperature seems to be measured to an extreme precision. A outdoor of -9 °C (15.8 °F) and a room of 2,000 °C (3,632 °F) have a difference around -9555.292C

Outside

Spaces that are not enclosed are simply considered "outside". The outside temperature is defined entirely by the climate and storyteller. No amount of heat adding/removing can change it, not even the Mod Tools can change it by simply adding/removing heat to the outdoor "room" - unless they set it for the entire map, nothing will happen. Proximity to heatsources does not matter. Instead the "outside" value is used.

Despite this "outdoor" is still used like any other neighbouring room for wall equalisation. And often the most important room for that matter.

Rooms can be in one of 3 states:

Unroofed (not a single roof tile). This means it will simply use outdoor temperatures. It does still count as a "room" for most game mechanics, but for temperature mechanics every active tick it will set to outdoors temperature regardless of difference.
fully roofed (all tiles in the room have a roof tile). These rooms are entirely subject to heating, cooling and temperature equalisation
partially roofed (uses outdoor temperature) while this room seems to maintain temperature while paused, the next equalisation tick will simply set it to outdoor temperature as a fully unroof one
partially roofed (not use outdoor temperature) While there will be significant equalisation via the (lack of) roof, the room still has its own temperature calculation. The exact flipover point between this and "uses outdoor" is not static and seems to change with roomsizes. Possibly something based on the summed "no roof equalisation" value. < 1/4 of all roof tiles seems to be the limit.

Passive Equalisation

This is equalisation via walls and roofs.

Walls will equalize towards the room on the other side. This can be another fully realized room or simply the outdoors. If the other side is not outdoors, that room will also equalize towards this room.

The material of the walls does not matter. Wood is as isolating as any stone or metal. And unmined rocks are equally effective.
The surface area does seem to matter. Basically, the game is using a 2D variant of the square-cube law, with walls taking the place of "surface area" and room size taking the place of "volume". As such square rooms are the most efficient at keeping temperatures.
A 2nd layer halves the temperature equalisation via walls. Adding more than a 2nd layer of wall does not seems to have any effect.
Furniture acts highly variable for this and even just the definition what is a room. Nutrient dispensers are one of the few items working fully like walls for equalisation purposes

Example wall equalisation values at -9555.208C difference:

1x1: -161.470°C
2x2: -81.235°C
3x3: -54.157°C
4x4: -40.618°C
5x5: -32.494°C
6x6: -27.078°C
7x7: -23.210°C

Example double wall equalisation values at -9555.208C difference:

1x1: -81.234°C
2x2: -40.617°C
3x3: -27.078°C
4x4: -20.309°C
5x5: -16.247°C
6x6: -13.539°C
7x7: -11.605°C

Roof is a major part with equalisation with the outdoor temperature. It will always equalize with the outdoor temperature, regardless what the room borders. However, the equalisation rate is also constant for all room sizes at the same temperature difference. There are 4 basic types of roof:

unroofed
Constructed (Thin Roof)
Thin Rock (Thin Roof)
Thick Rock

Thin Roof at a difference of -9555.208C it is -57.331°C.
unroofed tiles are looked at in relation to the total count of roofed tiles. With at least 1/4 unroofed the room will simply equalize to outdoor temperature on the next tick.
thick roof isolate the same as thin roof. However, they also add a cooling effect if indoor temperature is above about 15 °C (59 °F); this effect is extremely small compared to other sources, however

Active Equalisation

While Vents, Coolers and open doors still keep rooms separated, they also equalize temperature at a very high rate. This rate is unfortunately not shown on any tooltip.

Torches, Campfires, Heaters and Passive coolers will directly modify the room temperature instead, adding/removing heat every equalisation tick as appropriate for their settings/current state.

Architect

Temperature: Campfire • Heater • Cooler • Passive cooler • Vent