Hayboxes (Insulated Cookers) - Capturing heat: Five earth-friendly cooking technologies and how to build them

When the sun isn't shining and people are cooking with wood, a lot of energy can be saved by using a haybox. (Hayboxes are sometimes called fireless cookers.) After boiling the food for a few minutes, the hot pot is placed inside an insulated box, where it finishes cooking. The retained heat is enough to simmer the food to completion. A haybox does all of the simmering for us, saving not only energy but effort as well. Saving the firewood that wastefully went into simmering the food results in tremendous savings!

A haybox also makes cooking much easier. No more dealing with watched pots to guard against boiling over or scorching. At Aprovecho, we usually make lunch while getting breakfast. All we do is quickly boil up the beans and rice and then pop them into hayboxes where they'll emerge hot and ready for lunch. It saves a lot of time and effort.

Hayboxes have been used for centuries in different countries.

They work by keeping food hot enough (over 180 F.) for cooking to continue. The design criteria are simple:

Make sure that there is plenty of insulation around the pot, especially the bottom and top.
The pot should fit into the box as snugly as possible.

The lid on the haybox should make a good, airtight seal.

A wide variety of materials, besides hay, can be used for insulation. Remember that any material that traps isolated pockets of air will insulate well. Examples of insulation are: straw, rushes, chaff, popped grain, wood shavings, sawdust, newspaper, fiberglass, feathers, cotton, sponge, fur, wood ash, charcoal, etc. If you use one of these, allow 4" of wall thickness. If you use cork, cardboard, aluminum foil, styrofoam, rigid foam, etc. you can reduce the thickness to two inches.

One of the most efficient hayboxes is made by filling the air space around the pot with cushions, held in place inside a box.


Fill the space around the pot with cushions.

Another simple method is made from two boxes, one inside the other. The space between the two boxes is filled with insulation. An insulated lid or cushion fits over the top.


Two boxes with insulation between them.

Or we can invert the box and have it sit upon an insulated base on which the pot also rests. Raising the pot up onto another higher platform, like a piece of plywood, makes a double seal to keep air from escaping.


An insulated box resting on a platform.

Another type of haybox is made from a double bag of material lined with insulation. A draw string closes the top. The neck of the bag should open wide so that the pot can enter and be withdrawn easily.


A double bag lined with insulation.

A haybox can be something very simple, like a hole in the ground that is filled with hay, straw, etc. The pot is placed inside the hole and covered by thick layers of insulation. The hole could also be made in a block of sand/clay mixture above ground so as to be more easily reached.

Simmering food in a haybox will take about one and one-half to three times longer to cook than on a cooking stove. A large mass of food works better than smaller amounts. A tight lid on the pot helps as well. Using one quarter less water with grains is better since less water is lost to evaporation. It's possible to wrap the pot in a towel before putting it in the haybox.

Bacterial poisoning can be avoided by two simple steps. Make sure that the food is initially boiled for at least 5 minutes. Then keep the lid closed from that point on and reboil meat dishes before serving.
We can't imagine cooking now without hayboxes. They're truly one of those rare devices that save energy and make life simpler at the same time! We've used them for more than ten years and highly recommend them. Hayboxes are so fuel efficient, because the haybox does all of the simmering "for free", without using energy that would have mostly gone into making steam, anyway. The Rocket stove/haybox combination is capable of cooking with very small amounts of bio-mass. And, this method is easier, safer, and more convenient!