Wednesday, April 20, 2011

The Sustainability Review - The Hay Box

By Mike Forbes, Co-op Volunteer Writer

When you cook food much of the heat energy from your stove is used to overcome heat loss from your food to it’s surroundings.  Couldn’t we insulate our food so heat isn’t lost as rapidly thereby using less energy to cook it? Definitely.

Rice. Theoretically, once the rice boils the heat energy needed to complete cooking is present.  The heat leaves the rice because the food is insulated poorly. We overcome this loss by turning the burner down low and simmering it for 30-40 minutes, wasting electricity or fuel. 

What if we boiled the rice and then quickly put it in an insulated box where the heat energy couldn’t escape and the rice would then finish cooking? 

The catch is building a box that heat can’t escape from. What I’ve done successfully for years is build various insulated boxes from commonly available items.

I use them primarily for keeping food hot for a LONG period of time and cooking beans, millet and quinoa.  I’ve also been known to use it for steeping grains and preparing yeast in the beer making process…  If I put a hot food into the box I can pull it out 2-4 hours later still piping hot.

The trick to maximizing efficiency is to build a box that has as little air in it as possible with the largest pot you expect to use. My boxes are built from rigid foam insulation with a radiant barrier (shiny aluminum coating toward the inside).  I glue them together with hobby glue or foam adhesive (Natural Abode and MBS both carry non-toxic, low VOC glues that work well).  I put little strips of wood on the inside bottom to keep the hot pots directly off the insulation.  The door is just a rectangle of foam that wedge fits into the box. It is critical to make the door tight fitting, if you put a slight bevel to the door it will create a much better seal.  Using a table saw to make your cuts makes the process very easy and accurate.  Options for dressing up your box cosmetically are endless.  I typically wrap them in wood to make them more visually appealing but for years had a silver box wrapped in duct tape sitting on top my refrigerator.

If you build the box to your largest pot you can still use smaller pots with good success if you add more thermal mass to the box.  I found that filling small jars with hot water works well to eliminate these air spaces.

Currently we are planning on converting one of our kitchen cabinets into a haybox.  We’ll incorporate insulation into the door with the taper fit foam as mentioned earlier.   It is my understanding that this concept is old and that traditionally hay was used in the boxes as insulation, hence the name hay box.

Mike welcomes questions.  He can be reached at


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