Introduction: Resurrecting the California Cooler

About: By day I'm a mechanical engineer at a university laboratory. In my free time, I do my own projects.
Coastal Northern California is blessed with a very moderate climate, generally on the cool side, especially at night. Before the refrigerator became common in households, denizens of this region took advantage of the cool weather by storing perishable foods in a special kitchen cabinet that brought in air from the outside -  the "California Cooler."

When the refrigerator came along, it seems that, over time, the vents were boarded up and the California Cooler was all but forgotten. Today, if you walk the streets of my hometown, Berkeley, where most of the houses were built in the 1920's, you will see many homes, and even apartment buildings, with the exterior vestiges of these vents.

My house is such a house. When we decided to remodel our kitchen in early 2009, I came up with the idea of opening the vents and bringing our California Cooler back to life. What better way to conserve energy in this age of green thinking than to keep foods cool with outside air? This is the story of the resurrection of a California Cooler.

Step 1: History of the California Cooler

Most of the information I have found on the Web about California Coolers consists of blogs dealing with kitchen remodeling.. This blog ( has some interesting information. The author says that the California Cooler came into existence in 1910, not in the 19th century as I would have thought. I may have to go to the library to find out more about the history. Below are a few more interesting links that I've found.

In this link someone is remodeling their kitchen and debating whether or not to keep the CA Cooler

Below is a gallery of California Cooler photos that I shot in South and West Berkeley, actually photos of the exterior vents which, presumably, are all boarded up. They are VERY common around here and the majority of them seem to be floor-to-ceiling pantries. Our single, large vent seems to be very unusual.

Step 2: The Basic Idea

When I started this project, what I had in mind was the following:

A. Re-open the wall vents and have a special cabinet designed to function as a California Cooler.
B. Add insulation to the cabinet.
C. Make the vents louvered so they could be closed and opened.
D. Keep an indoor-outdoor thermometer probe in the cabinet to monitor the temperature.
E. Purchase a much smaller refrigerator for our new kitchen to go along with the CA cooler with the intent of saving electricity. I have known for some time that some foods that are commonly kept in the fridge don't need to be kept there, such as eggs and butter, and others, like tomatoes, may even be harmed by refrigeration.

Step 3: Materials We Used

Cabinet: A custom cabinet 44 x 21 x 12 inches inside

Wall Insulation: RMax rigid polyurethane insulation 1-inch thick (photo below)

Weather Stripping:

Interior Lining: 1/2 inch maple plywood

Shelves: Wire Cloth held up with standard 5 mm shelve pegs

Thermometer: Oregon Scientific Wired Indoor-Outdoor Thermometer

Step 4: How It Was Done

(See photos below for sequence)

A lot of the credit for actually making it happen goes to our kitchen re-modelers, Eric Christ of Halperin and Christ Building and Design and his nephew  Noah, as well as the cabinet maker, Jeff Ward. First, they removed our old cabinets and exposed the old vent. This was a single vent that was fairly large. Perhaps it was divided into two vents originally, but what we needed for the dimensions of the new cabinet was to seal off some of this vent and then to cut a new one up higher.

When the new cabinets arrived, they cut holes in the back for the new vents before installing the cabinet on the wall. For louvers, we used a pair of heating registers with little levers for opening and closing. After the cabinet was installed, the new vent was cut in the side of the house to match the upper cabinet hole (See Intro Photo). A strip of adhesive foam insulation was also added along the vertical edge, to prevent air exchange with the kitchen.  Soon similar pieces of insulation will be added at the top and bottom.

Next, we added insulation to the back and sides of the cabinet, and Eric made some custom pieces of wood to cover the insulation and line the cabinet. The wood and insulation in the back was given holes that matched the vents and into these holes the heating registers were mounted.

On the side walls, we drilled sets of holes for the shelf pegs. The wire cloth was cut with a grinding wheel, and then bent to the right size by a metal shop.

Finally, insulation was cut for the door. It has not yet been permanently installed (still trying to figure out how to do this), but it's put in place for most of the day, except when we are home, cooking.

For now, the thermometer probe has just been inserted through the gap at the bottom of the door, but soon we'll drill a hole in the bottom of the cabinet and mount the thermometer on the wall.

Step 5: The Results

January 5, 2011
The California cooler is now just over a year old. We are now at the coldest time of the year and it's working great. One thing that has been bugging me is that I have no way of knowing how much energy the California Cooler saves. Probably the biggest savings is that we got a smaller refrigerator when we remodeled the kitchen and then the CA Cooler could be a little savings on top of that. I've decided to collect some data that may shed a little bit of light on things. I'm going to measure the energy consumption of the fridge for the entire year, and also record the outdoor, kitchen, and cooler temperature on as many days as possible. Maybe after another year I'll have a better idea of how the cooler reduces the amount of electricity used for the refrigerator.

November 8, 2010
After that heat wave in June, we had the coolest summer in at least 30 years. During that time the California Cooler worked as well as could be expected - the temperature varied from 60-65 most of the time - we still kept eggs, peanut butter, cooking oil, carrots, parsley in there, but not butter.

In August, our "indian summer" came and we had warmer weather for the next two months. We had to completely stop using the CA Cooler during that time. It wasn't much of a problem to fit all of our food in our small fridge. Maybe next year I'll get around to trying some of the ideas appearing in the comments. The two that interest me the most are: 1. evaporative cooling a la a swamp cooler and 2. A solar powered peltier cooler.

In late October, our version of fall began and now the cooler is in the low 50s in the morning, and goes up to around 60 during the day. We've started using it again and, as the weather gets colder, we should be able to add more and more items and we should be able to use it continuously until at least next June. Then we'll see what kind of summer is served up.

June 30, 2010
We had a mini heat wave and during that time the cooler didn't work well at all (went above 70 F). Fortunately, that only lasted 2-3 days. Now we are back to our typical summer pattern: 70-75 F during the day and a low of 57-59 at night. I put in the cool thermal masses in the morning before I leave for work and close the vents. The temperature swing under these conditions is about 60 F minimum and 65-67 maximum. If I watch the weather report, I could consider putting some ice in the cooler during abnormally warm days.

May, 2010
The spring has turned cool and the CA cooler is working quite well (staying below 65 F during the day).

April 4, 2010
With the warmer spring weather, I have given up keeping the temperature below 60 F and settle for a maximum of about 65 F. However, it always goes down into the 50s at night, which is why a CA cooler can work in N. California. I am using more water for thermal mass (about 3 gallons at this point) and there are certain foods that we probably won't store during the warmer months, like strawberries.

February 17, 2010
Our short Bay Area winter is coming to an end. We had a week of temperatures in the mid 60s and the CA Cooler went as high as 65 F one day. I would like to keep it below 60 F if possible, and this will become a challenge as the year progresses. I have increased the amount of cool thermal mass (bottles of water) that I put inside the cabinet every morning and remove in the evening. On a couple of days I also tried putting in 2-3 ice gel packs from our freezer and closing the vents in the morning. That worked just fine but, of course, it takes electricity to freeze those packs.

Another idea that I got from a reader's comments is to try putting a damp cloth inside, in the hopes of getting evaporative cooling. A couple of times I hung a damp cloth from one of the shelves, but, it didn't seem to have worked I will experiment some more with the location of the damp rags.

February 10, 2010
The CA Cooler is now pretty much finished. The door has built-in insulation and also weather stripping at the top and bottom edges.

January 10, 2009
We were away on vacation for 2 weeks and the CA Cooler stayed below 60 F the entire time.

December 10, 2009
We have been having unusually cold weather, with temperatures in the 30s at night. I have seen the temperature difference between the kitchen and the cooler as high as 23 degrees F. The coldest I have seen the cooler get is 39 F. I then decided to close the vents on the coldest nights, because I didn't want it to get so cold.

December 3, 2009
We have been using the CC for about three weeks and we love it! For the first two weeks, we didn't have any insulation on the door and the temperature inside the cooler was between six and ten degrees Fahrenheit colder than the kitchen temperature. Typically, the cooler has gone down to the upper forties at night and up to the high 50s or low 60s during the day.

We have been keeping eggs, butter, oils, peanut butter, apples, onions, tomatoes, broccoli, cilantro, parsley and strawberries inside it. It turns out that we keep so much food in the cooler that there is plenty of room in the small fridge for the rest. It's not even an issue - our old fridge was always more crowded with food than this one is.

I also keep a gallon bottle of water and two quart bottles in the top shelves to act as thermal mass in order to keep the temperature lower during the day. I can increase this effect by leaving those bottles out at night, so they get as cold as possible.

Last week, I added a layer of insulation behind the door. It's still not permanently attached to the door, so we keep it on overnight and when we're gone during the day. Now, the temperature difference between the cooler and the kitchen is between ten and seventeen degrees F, which is excellent. The weather lately has seen temperatures in the mid 40's at night and in the upper 50's during the day. The cooler goes down to around 46-50 F at night, and up to 57-62 during the day.

summer, 2009
We committed ourselves to buying a very small refrigerator at the beginning of our kitchen remodel. This refrigerator would have 10.3 cubic feet of volume, compared to the 16.6 cubic feet of our old fridge. As the kitchen remodel progressed, we sometimes got cold feet. "What will we do if the California Cooler doesn't work and we have to fit all of our food in that tiny fridge?"

Step 6: Is There a Future for the California Cooler?

Update March 2021

A reader pointed out that a CA Cooler that goes from floor to ceiling and has the intake air come from the crawl space or basement, instead of outside, would do a better job of cooling, because those spaces don't get hot in the summer. I think the ideal would be to be able to switch between outside air when it's cold weather, and basement air when the weather is warmer.

Update October 2014

We have had the CA cooler for several years now. We still keep the same types of items in it - butter, tomatoes, eggs, some oils, peanut butter. Overall, I would say that it's not worth it for someone remodeling their old house to spend a lot of money resurrecting their CA Cooler, nor to add them to new houses. I think the main lesson we have learned is we can get by with a smaller refrigerator, and I suspect that most households could do the same. That would be a great energy saver, but the trend for a long time has been for households to buy ever larger fridges.


A couple of mornings ago as I road my bike to work, I decide to see if I could spot any California Cooler vents on houses. Not surprisingly, I found a bunch. They are very common in the flats of Berkeley, not just on single family houses, but on old apartment buildings. It seems like the majority of them are for floor-to-ceiling pantries. Yesterday, I surprised myself even more by counting that more than half the houses on my block have them, as well as one apartment building (I will definitely be asking my neighbors if I can take a peak inside their kitchens to see what has become of their California Coolers!).

I can imagine that people in the 1930s were excited to get their new-fangled refrigerators and that continuing to use the primitive California Cooler would have seemed ridiculous. But we live in a different era now, one in which using renewable energy is preferable. The cool air that we have along the California coast comes to us free of charge via winds and currents of the Pacific Ocean.

I have a fantasy that others will resurrect their California Coolers as we have done. But, from a green perspective, does it really make sense to do this? I think that our method of storing some foods in the California Cooler, and others in the refrigerator will definitely use less energy that we did before. According to a Federal Trade Commission Document our old refrigerator used 464 kilowatt hours and our new one 309 kWh per year, for an annual savings of 155 kWh. That's about enough energy to run our entire household for 17 days. Not bad for a cabinet with two vents in it!

But, when I think about how much it cost to make the cooler, it's actually kind of embarrassing. I think it cost at least as much as a brand new refrigerator! Of course, most of the expense was in labor, and we also chose to use pretty expensive materials because we wanted it to look really nice.One choice that could have been made differently was the use of polyurethane insulation. This is a non-recyclable petroleum product. If I were to do it again, I might choose some other type of insulation, such as recycled denim. However, I'm not sure that other types of insulation would do such a good job, or work for a long time with moisture present.

If you live in an old house that has a boarded up California Cooler, would you consider doing something like this? I'd love to hear comments from you. If you are a builder, would you consider putting a California Cooler in a new house?

Also, out of curiosity, I'd be interested to hear from people in other cities where houses were built between 1900 and 1930. How common are California Coolers there?

I actually think that resurrecting the California Cooler is a subset of a larger energy saving idea - to use outdoor air to aid refrigeration. Under certain conditions, it could be more efficient for a regular electric refrigerator to exchange air with the outdoors instead of the air in your kitchen. And, in certain places, during certain months, it's cold enough to use outdoor air as a freezer. Imagine if in places like Minnesota if people had the choice to operate their freezer with outside air in the winter and then use it normally in the summer. That could save a lot of energy when compared to running a freezer in the winter while heating the air inside the house for comfort. I have started doing little things to make our fridge not work as hard. For example, when I cook a big pot of soup, I let it cool down to room temperature until putting it in the fridge. Sometimes I'll leave something out overnight (if it doesn't have a smell that would attract animals) and then put it in the fridge in the morning, shaving off the amount of cooling the fridge needs to do on that item.