Thermal Cooker and Passive House

Several times a year, we host a tour of Midori Haus to share our knowledge and experience of remodeling an old house to be green (healthy, energy efficient, water efficient, and sustainable). We delight in explaining what Passive House is and showing how features of Midori Haus reflected Passive House principles. At the last tour, we were pleasantly surprised to learn about a cooking method that embodies Passive House principles: energy efficient cooking within airtight vessel with good insulation.

One of the visitors brought along a thermal cooker. This is an efficient appliance that uses very little energy and effort. The food is cooked in a thermal cooker pot on a stovetop (gas, electric, or induction) and brought to boil for about 10 minutes. Then this pot is inserted into a thermos-like enclosure that cooks the food with residual heat.

Brilliant, isn’t it?

I used to think slow cookers or crockpots were pretty energy efficient. Now, I can see that slow cookers are like coffee makers (coffee stays warm by sipping electricity) and thermal cookers are like a thermos (coffee stays warm for a long time without electricity). When the hot food is placed in the well-insulated airtight enclosure it only loses heat at the rate of 4 ~ 5 degrees Fahrenheit per hour. If the temperature of food in the inner pot is 200 degrees when it’s taken off the stovetop and placed into the outer container, eight hours later it would be about 160 degrees, still plenty hot. Because there is no additional heat applied to the cooker, it won’t burn. I find this feature attractive since I’ve burned edges of stews in my slow cooker.

History and Food for Thought

The principle of thermal cooking has been around for a long time. I invite you to read this article from Low Tech Magazine, "If We Insulate Our Houses, Why Not Our Cooking Pots? " It explains why cooking is so inefficient and covers the history of fireless cooking with striking images. If you prefer to watch a short video instead of reading about low energy cooking history, then take a look this video titled, “A Bit of History About Thermal Cooking.

Selection Criteria

Our visitor recommended the Tiger brand of thermal cooker, which she brought. I placed the inner pot onto my induction cooktop to see if it was compatible with induction. It was. What else shall I consider before buying one? Performance (keeping food hot longer), durability (quality materials and good construction), and cost are what I typically look for, but these two videos gave me further insight:

Ecopot Thermal Cooker Comparison video advises to look at these characteristics:

· Pot’s locking mechanism

· Food cooking capacity

· Quality of inner pot

· Heat retention technology

· Technology used to avoid aroma bypass

· Ability to reheat food to 70C (above food safety standard of 60C)

Cindy Miller, author of Let's Make Sense of Thermal Cooking Cookbook, advises people to choose models that retain heat for 4 – 8 hours. The insulation type and capacity is explained in a show and tell fashion in this Types of Thermal Cooker  video.

I’ve heard that many recipes can be adapted for the thermal cooker. Perhaps I’ll try some of these recipes from Delishably when I get one.

About the Author

Chie Kawahara

Chie is one of the co-creator of Midori Haus. When she is not sharing her stories of transforming an old house and giving tours, she enjoys trail running and hiking.