A Definitive Guide to Efficient Freezers [1.4]

The basic structure of a freezer is simple. In fact, it's taught to you in the tutorial. A closed off room with one or two coolers set to a sub-zero temperature. Simple enough, right? Well, no.
This guide covers some of the well-known + lesser-known freezer structures, exploits, some of my personal designs and backs it all up with numbers. So next time when Randy sends a Heat Wave, you can chill out (pun intended) and focus on making more hats like you are used to.

Let's Talk About Freezers

The basic structure of a freezer is simple. In fact, it's taught to you in the tutorial. A closed off room with one or two coolers set to a sub-zero temperature. Simple enough, right? Well, no. Any player who has player RimWorld for several hours knows how tricky freezers can be. Solar Flares, Heat Waves, even a broken-down cooler could cause a catastrophe.

And with Biotech adding an endless supply of Toxic Wastepacks, it's all the more important to build an efficient freezer for your colony.

This guide covers some of the well-known + lesser-known freezer structures, exploits, some of my personal designs and backs it all up with numbers. So next time when Randy sends a Heat Wave, you can chill out (pun intended) and focus on making more hats like you are used to.

Prerequisite

A few things to keep in mind before we begin.

• All the tests have been done in Vanilla RimWorld + All 3 DLCs [No mods]
  
  
• All the tests have been done in Extreme Desert + Heat Wave [Outdoors: 50C]
  
  
• The area of the freezer matters. The room interior size is 9x9 in all tests.
  
  
• While I have built all the structures with Slate, the used material does not matter in the slightest. Wood has the same level of insulation as Plasteel.
  
  
• Floor / No-Floor does not matter. None of the tests have been floored.
  
  
• Contents of the freezer does not matter, unless it's something that actively heats up the room. Like Torch. [More testing needed on this one]
  
  
• The temperature the coolers are set to, does not affect the minimum reachable temperature for a freezer, but it does affect the efficiency. A higher temperature [-10C] would result in the coolers getting to the low power state quickly, saving you power. A lower temperature [-50C] means you'll have more time before the freezer heats up in case of a Solar Flare.

Standard

This is the most basic structure of a freezer. Something you have probably built when you first played the tutorial. With a 50C outdoors, two freezers managed to cool down the room to 6C, so a 44C reduction. We'll use this as a baseline for all the other freezers.

So, how can we improve upon this one?

Mountain Freezer

Overhead mountain tiles are pretty much the cheat code for efficient freezers and will remain so throughout the guide. Building the standard freezer under overhead mountain tiles brings the temperature down to -8C, a 58C reduction!

For all the other designs, I'll avoid making a separate section, and just post the overhead mountain result alongside the standard one.

Double Wall Freezer

Overhead mountain tiles are amazing, but it's not always feasible to build your freezer under them. What other options do we have?
Double thick walls! Double thick walls improve insulation. Resulting in a lower temperature. -6C means a 56C reduction, which is almost equivalent to single thick wall with overhead mountain tiles!

If you are wondering, why do I have the doors lined up that way, it's because they form an airlock. In RimWorld, when you open a door, the game tries to normalize the temperature of the rooms it's connected to. The airlock ensures that minimal amount of outdoors air comes into contact with the indoors air when the doors are opened.

The one tile gap between them is important. Without that, both doors will be opened at the same point.

Obviously, if you manage to build double thick walls under overhead mountain tiles, that outperforms both of them by a significant margin. With a temperature of -29C, this design achieves a 79C reduction! Giving you considerable amount of time to prepare for a solar flare even during a heat wave.

Remember, double thick walls are the limit. Making triple/quadruple thick walls won't improve insulation in the slightest.

Chimney Freezer

The last design seemed perfect. So, what's the problem? The problem is the fact that Coolers have really bad HP, and raiders love to destroy them on sight. A way to protect the coolers would be nice, but how can we vent the hot air if we also have to protect the coolers?


In RimWorld, if a room is less than 75% roofed, it's considered outdoors. And an outdoors room normalizes its temperature with the outdoor temperature. We abuse that fact, and the fact that coolers can be used as walls to form a "Chimney" of sorts. A single unroofed tile insider the freezer is filled with a barricade and surrounded by Coolers.

The barricade prevents drop pod raids, while the unroofed tile allows the hot air from the coolers to escape. This design cools the freezer to -5C, a 55C reduction. Almost equivalent to Standard Double Thick design or Single Thick Overhead design.


Since you need to have a very specific tile unroofed among all the overhead mountain tiles, this design is probably not viable in an un-modded playthrough. Partial overhead tiles work, but not as good as the complete structure. But if you manage to build it, this design is even more efficient than the Standard Overhead Double Thick design, getting as low as -34C, a whooping 84C reduction!

While this design is the best one, we had so far, there is a drawback to it. We are sacrificing 3 spaces inside the freezer. 3 spaces might not seem like much, but remember now shelves hold 3 items, so you are actually sacrificing 9 spaces worth of storage. So, how can we improve upon this design?

Airlock Chimney

To improve upon the last design, we turn to the most broken mechanic in the whole game. No, I am not talking about Pain is Virtue. I am talking about DOORS!

Doors are, for the lack of a better word, weird. A door tile has its own ecosystem. Its temperature is supposed to be the average of the rooms it's connected to. An unroofed door tile is even weirder. It works as a chimney, while being indoors.

You might be thinking, so what? We just replace the barricade with a door? No! Look carefully, we already have a door inside the freezer. We'll just reuse it.


The red colored door is unroofed in this design. The two coolers use that as the chimney. This design somehow reaches even lower temperature than the standard Chimney, for reasons we'll discuss later. Moreover, this design also does not waste the 3 spaces as the Chimney design. With a minimum temperature of -15C, we can achieve a reduction of 65C using this structure.


The overhead design also achieves a temperature lower than its predecessors, -38C with a reduction of 88C than its surroundings.

This, my friends, is the best Freezer design I currently know of that does not use any exploits. If you think badly of exploits, you should stop here.

No? You are just like me, huh? Okay then, let's see how can we possibly improve upon this design?

Open Airlock Chimney

Remember what I said in the Airlock section?

when you open a door, the game tries to normalize the temperature of the rooms it's connected to.

And what did I say in the Doors section?

A door tile has its own ecosystem. Its temperature is supposed to be the average of the rooms it's connected to.

What do you get when you combine these two?


While I don't fully understand what's happening here myself, my theory is this. The game checks for the cooler hot air less frequently than the door ecosystem temp. So, when the hot air is released, it quickly goes away through the unroofed door.

Now the opened door ensures that the temperature of the freezer, and the small airlock room will be the same. And the door ecosystem ensures that, the temperature of the door is the average of the rooms it's connected to. Which, in this case, is the temperature of the freezer.

The limit to how much a cooler can cool down a room depends on several factors. One among them is the temperature of the hot side [you can chain coolers one after another to reach lower temperatures]. Since, in this case, the hot side is as cool as the cold side, the cooler can cool down the room further. Resulting in -30C, an 80C reduction, almost equivalent to overhead mountain tile on standard double thick design.


The overhead design blows everything out of the water by cooling the room to -85C, a mind blowing 135C reduction. While it's hard to achieve in an unmodded game, a partial overhead tile also provides exceptionally good results.


Infact, if you build the whole structure under overhead mountain, and aren't able to remove the tile, you can still achieve a temperature better than most other coolers available.

Conclusion

Other than the last Open Airlock Chimney, I have not "invented" any of these designs. These are just things I have picked up from several other guides, playthroughs and comments over the years.

If I have missed something, please comment it down. I'll happily add it to the guide crediting you for the addition.

This is my first guide on RimWorld. If you liked it, or learned something new, please consider giving it an upvote.

Sincerely,
Ashen Cone

[Mask of Humble]

@MAGNVS @Yukimaru the paste dispenser does count as a double wall, it was actually intended to be used as such from the start

[IMEI]

I have a few questions for you:
1. In each test, what temperature were the coolers set to? You mentioned that a cooler set to -10C means it goes into the low power state faster and -50C takes longer to have food spoil, but never mentioned what the coolers were set to during your tests.
2. With the airlock chimney testing, which tile is unroofed? The inner door or the outer door?

[MAGNVS]

@Yukimaru very good question, I am also curious

[Vistha]

Do the equations work the same if walls are in the FoW? For example I mine out a square in a mountain, so the second+ layer of walls is undiscovered.

I remember reading in the past that undiscovered walls were treated differently in some cases, but I don't remember if it matters for temperature.

[Master Basher]

Frankly, the wall coolers are even 'better' if you're thinking of a sturdy wall perspective. Just be wary on wall vents, if you don't want all that chill to bleed to everywhere else (unless that's by design.)

[stun]

Gotta be some crazy shit with 1.5 wall coolers/vents now

[TurtleShroom (HACKED, RECOVERED)]

I am confused with that last one. Is that room completely enclosed and completely under a roof? You said that if you make the heat sides of Coolers face doors, it negates the heat. Does that work with everything is under a roof, or does that door have to not have a roof?

[Yukimaru]

according to the wiki, paste dispenser function as walls, so does it count for the double-layered wall insulation?

[Dankius Memeius Meridius]

I learn something new everyday XD

[deadeye1114]

should note you can invert the open airlock chimney by swapping the freezer directions and including a roof to generate inf heat