A cold room is an invaluable asset for any market gardener. The first step after harvest is to precool the crops. Precooling refers to the rapid removal of field heat.

Crops harvested early in the morning, before the sun warms things up, have less field heat to remove.

Since any deterioration in crop quality occurs more rapidly at warm temperatures, the sooner field heat is removed after harvest, the longer produce can be maintained in good condition.

Eliot Coleman follows the recommendations of the USDA in the publication The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks (Agricultural Handbook Number 66). He has had great success following this handbook. You should definitely check it out for yourself to get even more valuable information on veggie storage.

Precooling can be done by immersion in or spraying with cold water. The colder the better. 

After precooling, produce should be kept cool in a spring house, root cellar, or refrigerated cooler (cold room). 

We will be focusing on the cold room for this article.

Cold Room

The cold room has three main purposes:

1. To cool incoming veggies from the garden by forced air: When produce is harvested, you must remove the field heat to stop it from spoiling. To maintain a high standard of quality, you must remove the field heat.
2. Storing veggies for extended periods of time: You gain a considerable amount more time to market any product when it is stored properly. It doesn’t have to be sold the next day. You can buy days to weeks of time to sell your harvest, depending on the type of product.
3. Chilling veggies to a point where they will stay fresh during transport, regardless of the ambient temperature of the delivery vehicle.

Two characteristics to keep in mind when you are going to invest in a cold room are the type and size of the refrigerated space, as both of these factors are very important in accomplishing the three purposes listed above.

Taking advice from the market gardener himself, J.M. Fortier, he recommends investing in a new air compressor with a warranty as refrigerator repair people charge about $100/hr. 

Also, he recommends setting up a larger cold room than you think is necessary. It is not overkill to get double the capacity needed for your current level of production.

It’s better to not limit yourself by underestimating your future needs.

As well, a large size cold room comes with advantages that should not be overlooked.

Advantages of a Large Cold Room

A large cold room with a powerful compressor will be better able to handle the incoming heat from frequent trips in and out at harvest time.

The best way to bring veggies to their ideal storage temperature is to have a cold room that actually stays cold.

Additionally, having a refrigerated space that is not filled to capacity will allow air to flow more freely. Air circulation plays an important role in cooling veggies. For this reason, it is a good idea to allow for a 4” space between stacks of bins.

Finally, it is much easier to manage the contents of your cold room when you have a large space to work in. 

Different sections of the cold room can be devoted to specific veggies, and it is much easier to maneuver a cart full of bins when you have extra space.

The cold room on J.M.’s farm measures 8 ft. by 16ft., and it was only in their fifth growing season that they began to occasionally fill it up completely.

Cold Room Organization

Choosing the right storage bins for your veggies is important. This will involve shopping around and checking out which models are available and right for the job.

Ideally, storage bins should have the following features:

• Sized correctly: not too small, but not so big that they are too heavy to carry when full of veggies. Using three different sizes of bins is a good idea: one for leaf veggies, one for root veggies, and one for fruit veggies.
• Closable lid: this allows bins to hold in moisture and prevents veggies from drying out in the cold room.
• Nestable and Stackable: they need to be able to support heavy loads when stacked and be sufficiently strong enough enough to last many seasons of intensive use.
• Easy to Clean: this is pretty self-explanatory.
• Well Draining: should have holes in the bottom to allow wash water to drain out.

You may not be able to find all of these characteristics in one bin, so some customization may be necessary. 

Types of Cold Rooms

Curtis Stone from The Urban Farmer has some great advice on types of cold rooms.

He prefers to use two medium-sized walk-in coolers than one large one. 

The nice thing about having two coolers is that only one of them is running constantly.

The other runs only on Thursday and Friday when they are packing for restaurants and the farmer’s market.

Curtis uses one cold room for produce that was just harvested and the other for produce that has been washed, portioned and packed.

The two cooler system keeps things organized and easy to find.

Some farmers choose to use a collection of home refrigerators as coolers. However, this is not advisable if you’re planning to farm commercially.

It is very difficult to fit containers from the field into a domestic refrigerator. The space inside is just too small.

Using home refrigerators would mean that you have to process and portion everything immediately when it comes off the field so that it will fit in the coolers, and this is not an efficient workflow.

Some farmers use commercial pop coolers (like at the grocery or convenience store). These can work for small operations, but you will probably need a few of them.

A good rule of thumb is if the coolers are not big enough to hold your totes, baskets, or bins, then don’t buy them.

The main problem is with these pop coolers is that if the compressor malfunctions or dies, they are not worth fixing. Heating and cooling repair are very pricey, as I have previously mentioned.

Recommended Cold Room Systems

Curtis recommends restaurant-style walk-in coolers or custom-built coolers using a CoolBot system with an air conditioner for a compressor.

These cooler choices are both economical and easily available.

You can find restaurant-style walk-ins online or at auctions, or find restaurants that are liquidating their assets. The restaurant industry has one of the highest failure rates of all businesses, so the turnover of equipment is quite high.

The next best option is to build a cooler yourself. There are many designs online, like this one or this one. 

You can frame up a simple room, any size you want. A standard size for a frame is 8ft. Wide, 8 ft. deep, and 6 ft. high.

There are lots of options for high-grade insulation and vapor barriers to choose from. The key to this design is the cooling unit itself.

Instead of buying a compressor, you can use a simple piece of electronics called a CoolBot; it modifies an air conditioner to act as the compressor. CoolBots also use less power than full-size compressors.

Bottom Line

Using a cold room on your market farm can help prolong the life of your veggies, easing the stress of having to harvest and sell all your veggies on the same day.

We do not currently have a cold room but are leaning toward building one ourselves and using a CoolBot system for cooling it. 

Don’t worry, we will be documenting the entire process of building a cold room when we start construction!

What type of cold room do you use? What are the advantages and disadvantages? Please let us know in the comments below.

Stay Local,

Kathy & Jon

your friendly neighbourhood growers