How to Build a Haybox Cooker for Off-Grid Slow Cooking

Estimated reading time: 19 minutes

There’s a fairly good chance you’ve never heard of a Haybox. Yes, it’s a box filled with hay, but it has a unique function that goes beyond hay storage. Think of it as the world’s first crockpot.

The idea is that a pot of soup, stew, or any hot food is placed in a box surrounded by an insulator like hay. If the box is sufficiently insulated, the hot pot will continue to hold its heat and cook whatever is inside over a period of hours.

Think of it as an off-grid slow-cooker. It’s a simple concept that follows the fundamental laws of thermodynamics, but there are various ways to make it work better. It’s sometimes referred to as “retained heat” cooking.

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The Box

The box for a Haybox can be made from anything including wood, metal, cardboard, and even plastic or fabric. As long as it’s air-tight and can hold the pot and the surrounding insulation, it can work.

Here’s one that’s made from a cardboard box lined with aluminum foil to help radiate internal heat.

You could also use a Mylar space blanket or even paint the interior silver. If you’re using a fabric cooler, many of them have a silver lining that helps to maintain temperatures—and now you know why so many coolers have silver-colored interiors.

We added an extra feature by painting the exterior of the box black. You don’t have to paint everything black. Instead, you could wrap your box in a black plastic garbage bag, black fabric, and even black paper.

The simple fact is that black things in the sun capture and hold heat, and that’s the whole idea with a Haybox.

You’ll also want to pay special attention to the lid on your Haybox. You want a good seal. Any kind of tape around the lid can work. It’s important to remember that heat rises, so if you have gaps or holes anywhere in your Haybox (especially on the top), the heat will escape. Do what you can to hold in the heat.

Box Alternatives

It doesn’t have to be a box. An insulated water cooler could make a very effective Haybox. So could a fabric or plastic cooler that you usually use to keep things cold. They’re insulated, and some even have a silver lining and lids that seal tightly. All you need to do is insulate it well and get that pot plenty hot before insulating and closing it all up.

Other possibilities include large stock pots, insulated metal milk boxes, or even a 5-gallon bucket. If the pot and the insulation fits and the lid seals tightly, you’re good to go.

Regardless of the box or alternative, it also makes sense to support the pot above the bottom of the box so the gaps underneath can also radiate heat. A simple trivet from a burner on a gas grill would work. You could also use some rocks. Doing this will allow some insulation to fit under the pot and keep the base off the bottom.

The Pot

A cast iron pot with a lid is best for a Haybox. The cast iron holds the heat better than most other materials, and the weight of the lid does the same. Aluminum is probably the worst choice because it tends to be thin and will lose heat the fastest.

Stainless steel can work if that’s all you have, but a small cast-iron Dutch oven is best. Then again, it you have a larger box, you can probably fit a larger Dutch oven. But smaller spaces in the box tend to hold the heat better, so don’t make your box too big.

Another important factor related to the pot is how deep it’s filled with water, broth, or stock. You’re going to bring your cooking liquid to a boil for a while before placing it in the box, and a full pot will hold heat longer.

Ingredients like vegetables or meat should also be brought up to a hot temperature with at least 5 minutes of boiling. The more heat they hold, the more heat they will give off in the box.

The Insulation

Hay is the traditional choice for a Haybox, but there are other materials that have insulating properties and are either available in nature or around the home or homestead. They include:

• Shredded Paper
• Sawdust
• Leaves
• Pine Needles
• Corn Husks
• Wood Chips

As long as the insulating material can create pockets and gaps to trap and hold heat, it can work in a Haybox.

In a pinch, you could combine materials if you don’t have enough of any one insulator. Blend it well and make sure it’s dry. Wet materials will draw heat and reduce the internal temperature.

The Location

A lot of this depends on the time of year. An ideal location is in a sunny spot during the summer. A black Haybox in the sun will have no problem maintaining a hot temperature for hours.

In winter, you could bring the Haybox indoors. If you have a sunny indoor location, all the better. You may notice some aromas from the Haybox, but they should mostly be the aroma of your food cooking.

Even on an overcast day or at night, a Haybox can do a good job of slow-cooking if you’ve put everything together properly.

Haybox Construction – Cardboard Box

We’re going to start simple with a corrugated cardboard box. The top flaps are folded down and in along the sides, and the box is then painted black.

The interior is lined with either aluminum foil or Mylar and held in place with some spray adhesive underneath and some metallic tape along the seams.

The bottom of the box is lined with your insulating material (we’re using corn husks).

The trivet—or some other way to hold the pot up and allow some air to circulate underneath—is then placed in the center.

The pot is placed on the trivet.

More insulation is carefully packed around the sides of the pot.

Finally, the pot is topped with more insulation.

We ran out of corn husks and finished the top insulation with leaves.

Cut a cardboard lid to fit tightly into the top of the box.

Spray the cardboard lid with black spray paint and seal with tape to make sure no heat escapes.

And now we wait. 4 to 5 hours is a good bet for a soup or stew, and a candy thermometer is a good way to assess progress.

If the temperature is still hot between 150 to 200 degrees F, you may have success.

Taste one of the vegetables or other ingredients to see if they’re tender and cooked.

If you’re good to go, it’s time to eat.

Haybox Construction – An Insulated, Fabric Cooler

An insulated fabric cooler is a great option for camping or when electricity is unavailable.

What’s great about a fabric cooler is that they’re portable and have a zipper that will seal in the heat to hold the temperature.

Follow the same process with a layer of insulating material in the bottom (we’re starting with leaves this time).

Place your trivet in place and add the pot.

Follow the same steps to surround the pot. We’re using hay for this step. Make sure you fluff up the hay to create those air pockets.

Top with more hay or corn husks until it is well packed and then close up and zipper.

Timing should be about the same depending on outside temperature, placement in the sun, and the color of the fabric. Figure the same 4 hours for a soup or stew.

If for any reason your meal needs more time, zip up quickly and let it rest for another 2 to 3 hours.

It’s not recommended to leave it overnight. We’ll cover some food safety tips later, but if the temperatures get low and the ingredients stew in cooler liquid, bacteria could develop.

A safe bet if your Haybox ever gets cold is to return the food to a boil for at least 3 minutes. That should give you some insurance against contamination.

Haybox Construction – A Large Stock Pot

If you have a metal stock pot large enough to hold a cast iron pot, you can make quick work of a Haybox. The primary benefit is that it already has a reflective, silver interior.

The downside is that the exterior is also highly reflective, so you’ll want to wrap it with a black plastic bag or other black material to capture any ambient heat from the sun.

You then follow the same pattern with insulation. We’re using hay top to bottom.

Fill to the top with insulation and place the lid on top.

Bunch up the black plastic bag and seal with some black tape to make sure the lid is airtight.

It’s a good idea to put a weight on the lid to make sure there are no small gaps.

Assume the same timing for a soup or stew with a test at the 4-hour mark for doneness.

Haybox Fails

Nobody’s perfect, and things can go wrong. Here are the most common fails:

• Air Leaks – This is the most common Haybox fail. Any hole, gap, or open seam will allow the heat to escape, especially if it’s towards the top of the box. Any kind of tape can be used to seal a potential leak including masking tape, painter’s tape, black tape, duct tape, or even mud or wet clay in a survival situation. All you’re trying to do is hold the air in, not make it waterproof.
• Pot Not Hot – You want your pot as hot as possible before putting it into the Haybox. It’s the only source of heat, and a full pot that has been brought to a robust boil for a few minutes will get things off to a good start. And try to use cast iron whenever possible. It holds the heat better and longer.
• Not Enough Insulation – Fill the bowl with your insulation and make sure it is tightly packed. You want to keep things hot or at least warm for several hours, and loosely packed or insufficient insulation will cause the trapped hot air to cool more rapidly.
• Half Empty Pots – Fill it to the brim. You want as much hot water, stock, and ingredients as possible. You might need to leave some headspace for things like uncooked rice or dry beans so they can expand a bit, but an inch of headspace is all you need. Otherwise, fill stews and soups to the top as much as possible. If you’re worried about your soup or stew bubbling over while boiling, add boiling water to fill the headspace before covering and placing in the Haybox.

Haybox Food Safety

The biggest fail with Haybox safety is when your food‘s internal temperature drops below 100 degrees Fahrenheit for an extended length of time. Water boils at 212 degrees F. and it will gradually cool, in the best Haybox. It’s literally a matter of degrees. As a general rule, temperatures below 140 degrees Fahrenheit could trigger bacterial growth.

Here are some things to do to ensure you don’t breed bacteria in a Haybox meal:

• Get the hot pot into the Haybox, insulated, and covered as efficiently as possible. Any exposure to air will cool the pot so try to be quick about it.
• Check the temperature when you think you’re done. Recipe times vary, and we’ll get into specific times for the recipes coming up, but it’s wise to know how you did before eating your meal.
• Return it to a boil before eating. The idea of a Haybox is to give you sustained heat over hours in an environment where that may be a challenge. Even then, if in doubt, you can always return the pot to a boil for at least 3 minutes to kill any bacteria that may have emerged in a low temperature pot. Note: You can’t do this with rice, but soups and stews are easily reheated over a small and temporary fire.
• If in doubt, throw it out. If the food in the pot doesn’t look right, smell right, or taste right, toss it and start over or cook with a different style of cooking. This can happen outdoors in winter on a cold and windy day when even the best Haybox may struggle to hold a decent temperature. Then again, you could always bury the entire Haybox in hay or leaves. You could also place it in a tent to see if that helps when the weather is below freezing.

Haybox Recipes

What follows are some of the classic Haybox recipes that have been used and developed by many people over time. All of them use a covered, cast-iron cooking pot and are presented across a variety of Haybox constructions.

Haybox Soup – French Onion Ramen and Vegetables

This is the simplest Haybox recipe and can be any type of soup you like. Here’s a sample of how to do this.

Ingredients:

• 1 package of French Onion Soup Mix
• 1 package of Ramen Noodles
• Chopped vegetable mix of onions, carrots and potatoes or any other vegetables you like or have available
• Enough water to cover and fill the pot
• Additional salt and pepper to taste

Directions:

1. Add the French onion soup mix, Ramen noodles, and vegetables to the pot.
2. Fill with water to just below the rim.
3. Stir to blend the soup mix and taste and add additional salt and pepper if needed.
4. Cover and bring to a boil over any small fire or on a stove.
5. Boil for at least 5 to 10 minutes. Watch for boil over if indoors and add more boiling water to keep the pot filled if needed.
6. Place the pot in the Haybox and insulate and cover making sure all gaps are tight or sealed.
7. Locate the box in the sun if possible and after 4 hours, open and check temperature and taste.
8. If done, serve and eat.

Haybox Stew – Beef Stew with Vegetables

What typically defines a stew is a thickened broth or stock with the consistency of a gravy and the addition of meat to the vegetables in the pot. Here’s a basic recipe.

Ingredients:

• 1 pound of beef chunks cut into 1-inch cubes
• Coarsely chopped carrots, onions and potatoes
• Beef stock or broth or enough salt and pepper to get the taste you want
• Enough water to fill the pot

Directions:

1. Brown the beef over a fire or on the stove until caramelized.
2. Add the onions and carrots to the pot and continue browning until caramelized. This will give your stew a good color and flavor.
3. Fill the pot halfway with water and stir to remove bits of meat and vegetables from the bottom of the pot.
4. Add the potatoes.
5. Bring to a rolling boil for at least 5 minutes covered.
6. Place the pot in the Haybox and insulate and cover and let rest for 4 hours.
7. Test and taste for doneness and serve.

A standard step with cooking rice is to allow it to rest with low heat so the rice can absorb the water. A Haybox can work quite well for this step, and it can take about an hour or two to fully cook the rice.

However, you don’t want to indiscriminately fill the pot with water like you did with the soup or stew. Rice needs to be cooked with exact proportions and a common combination is 1 cup of white rice to every two cups of water. Here’s the recipe:

Ingredients:

• 3 cups of white rice
• 6 cups of water
• 1 tsp. salt (optional)

Directions:

1. Add the 3 cups of rice to the pot.
2. Sprinkle the salt over the rice.
3. Add the 6 cups of water to the pot.
4. Stir to blend and settle the rice.
5. Bring to a boil over a fire or on the stove.
6. Cover and place in the Haybox and insulate and cover the Haybox.
7. After an hour, check the rice for doneness. If it is soft and fluffy with no sign of water in the bottom, you’re done. If not, cover the Haybox and give it another hour.

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