Temperature Guide: Cooling & Heat Management Tips

Temperature controls how heat is stored, moved and transformed in Oxygen Not Included; managing it is vital for duplicant comfort, machine reliability, resource processing and advanced cooling/heating systems.

Basic concepts

Temperature is measured in Celsius (°C) in-game; 0°C = 273.15 K. A 1°C temperature difference equals 1 K.
Heat is energy stored in mass. The change in temperature when heat is added or removed depends on an object's thermal mass (mass × specific heat capacity, SHC).
The game performs heat exchange in discrete ticks (0.2 s). If a floating-point calculation yields no change for either participant in an exchange, no heat transfer is applied — this produces practical lower ΔT thresholds for some materials and tiles.

Thermal properties and units

Specific heat capacity (SHC) determines energy per mass per degree (DTU/g·°C in game terms). Higher SHC materials hold more heat for the same temperature change.
Thermal conductivity (k) controls how quickly heat moves between adjacent objects/cells. Different rules apply depending on whether the transfer is cell↔cell or building↔cell.
Buildings have 1/5 the effective heat capacity of their materials for heat exchange calculations; that makes buildings heat up and cool down faster than an equivalent mass of tile or debris.
Insulated Tiles/Pipes use their own thermal conductivity (only the tile/pipe's k applies) and are far better insulators than regular tiles of low-conductivity material because of how the game mixes conductivities.

How heat transfers

Cell-to-cell conduction: heat exchanged is proportional to ΔT, the tick duration (0.2 s), and an effective conductivity (varies by scenario: geometric mean, arithmetic mean, lowest, etc.). Exact formulas are applied differently for solid↔solid, solid↔liquid, liquid↔gas, and building↔cell exchanges.
Building↔cell exchanges: include limits so a building cannot instantaneously reach an impossible equilibrium. The game computes an equilibrium temperature based on the building's heat capacity (C_building) and the cell's capacity (C_cell × area) and caps per-cell heat transfer so the building cannot exceed that equilibrium in a single tick.
Environmental exchange for creatures uses a capped thermal conductivity (k capped at 0.6), surface area and an insulation thickness parameter to compute per-tick heat transfer between creatures and the tile they're in.

Important implementation details and limits

Floating-point precision: 32-bit floats can cause very small heat changes to be ignored. For example, some Insulated Tiles require huge ΔT against massive bodies before any exchange occurs; low thermal-conductivity materials may not exchange heat below significant ΔT thresholds.
Heat transfer formulas use different combinations of thermal conductivity values depending on the interacting object types. Insulated objects typically use their own (lowest) conductivity rather than an average, which strongly affects design choices.
Heat is transferred per tick; large thermal mass differences can be limited by the building-per-cell maximum transfer calculation, preventing unrealistic instantaneous swaps.

Practical mechanics and tactics

Insulation and isolation

Use Insulated Tiles and Insulated Pipes to isolate rooms and fluids. Insulated Tiles use the tile's own k and are generally better at stopping heat flow into an adjacent medium than simply using a low-k regular tile.
Abyssalite and Insulite natural seams are very low-k, but because regular tiles average conductivities with adjacent materials, purpose-built Insulated Tiles often outperform seams for blocking heat to atmospheres and pipes.
Vacuum (Airflow Tiles into vacuum spaces) effectively stops most heat exchange for stored fluids if you ensure the stored content only contacts tiles in vacuum; Gas Reservoir contents exchange heat only with the output port tile and the tile below it — placing those tiles in vacuum prevents heat exchange entirely.

Heat sinks and thermal mass

Natural tiles (map tiles) typically have far greater thermal mass than constructed tiles and buildings; they are excellent temporary heat sinks. Mining removes half the mass and deletes half the stored heat, which can be leveraged to discard heat.
Large masses of liquid (water, crude oil, petroleum) are effective heat storage media due to their mass and SHC. Feed heated fluids into high-heat-capacity storage or flow through radiant pipes to move heat away.
Buildings count for less thermal mass than tiles/debris (1/5), so melting or converting buildings into debris/liquid can multiply the stored heat (useful for some exploits or endgame strategies).

Active cooling/heating devices and choices

Wheezewort: cools by absorbing gas in its base and releasing it 5°C colder; its effect is a fixed ΔT per packet, not an energy-based (DTU) value. It works best on high-density, high-SHC gases (Hydrogen yields the best absolute DTU/s effect).
Thermo Aquatuner and Thermo Regulator: move heat between a liquid/gas input and the building — they are heat-neutral (they move heat, they don't create or destroy it). Aquatuner removes a fixed 14°C from each liquid packet, so using high-SHC liquids and 10 kg packets maximizes efficacy. Aquatuners can chill to arbitrarily low temperatures (no minimum output), but cooling liquids below their freezing point in pipes damages them.
Steam Turbine: converts high-temperature steam into power and also deletes heat when combined with an Aquatuner in certain setups. Steam turbines have inlet caps and can waste DTU above certain steam temperatures if not configured correctly; designs often use multiple inlets and automation to maximize convertable heat-to-energy ratios.
Thermo-Nullifier and Hydrogen generation interactions: some late-game machines delete heat directly and can be net heat-negative depending on fuel temperature. Heating some fuels before burning can turn otherwise heat-positive generators into heat-negative ones.

Pipes and radiant piping

Radiant Liquid Pipe vs Radiant Gas Pipe: radiant liquid pipes generally outperform gas pipes because liquid pipes have 10 kg/s throughput vs 1 kg/s for gas pipes; combined with higher thermal conductivities of refined metals, radiant liquid piping transfers far more heat and is preferred in most exchangers.
Gas coolant use cases: hydrogen is the best gas coolant when needed because of its conductivity and very low condensation/phase limits. Gas pipes are useful for extremely high-temperature situations because gases do not have liquid boiling limits that damage pipes (liquid coolants can boil and burst pipes if used above their boiling point).
Radiant pipes exchange heat using the average thermal conductivity between pipe and coolant for regular pipes; insulated radiants use their own rules (check the material and pipe type).

Phase changes and flaking

Phase change occurs at 3°C beyond boiling/condensing/freezing thresholds: liquids evaporate at 3°C above their vaporization point and condense 3°C below their condensation point; freeze/boil in pipes damages them.
Partial evaporation/flaking: if adjacent tiles meet specific ΔT and mass conditions, the game can “flake” off 5 kg chunks at the phase-up temperature (used for tricks like converting Crude Oil → Petroleum → Sour Gas via hot tiles). Conditions require parent mass > 5 kg, donor sufficiently hot relative to parent, and adjacency at the right calculation stage.

Gameplay effects of temperature

Duplicant comfort: duplicants gain Chilly/Toasty Surroundings conditions if their average environmental exchange is too low/high for >6 seconds; these penalties affect Athletics, Stamina and Stress. Clothing, suits and warming stations can prevent these conditions.
Food spoilage: refrigeration mechanics use the lower temperature of the food and surrounding atmosphere to determine spoilage state. Refrigerated and Deep Freeze thresholds change spoilage multipliers (Refrigerated: <4°C, Deep Freeze: <-18°C).
Machine operation and failure: many buildings have operating temperature limits and minimum temperatures where they stop functioning (some machines will cease operation if their local gas gets too cold). Liquid/gas pipes can be damaged by phase changes; buildings can melt if exposed to excessive heat.

Tips and common strategies

Prefer routing pipes through tiles rather than open atmosphere for more effective heat transfer; buildings use a formula that multiplies pipe and cell conductivities, so solid conduction paths often move heat faster.
Use high SHC coolants (water, polluted water, brine, super coolant) for moving lots of heat; Ethanol is useful as a mid-game low-freeze coolant because of its low freezing point, but it has lower SHC than water.
Place heat-producing machines adjacent to large natural tile masses to localize heat; later mine out those tiles to delete heat when practicable.
For extreme heat (magma-level), use gas coolants or alternate-packet designs to avoid liquid boiling/damage. Use refractory tiles (obsidian, ceramic) and consider vacuum isolation for long-term containment.
When building steam turbine + Aquatuner setups, monitor inlet counts and temperatures to avoid wasting DTU; sometimes letting turbines waste excess power is acceptable if the goal is net heat deletion.

Manage temperature by understanding mass (how much heat you must move), SHC (how much heat each kg stores), thermal conductivity (how fast heat moves) and the game's discrete and capped exchange rules. Good insulation, appropriate coolants, careful placement against natural mass and attention to floating-point / transfer limits will keep your colony comfortable and your systems stable.