For quite some time now, I have had my doubts about some advances in technology and the definition of what really constitutes progress?

Today, modern glass greenhouse require massive inputs of energy to grow crops out of season. This is considered progress? This energy loss is due to the fact that every square meter of glass, triple glazed included, loses ten times as much heat as a wall, a thermal mass.

Producing crops in temperate regions did not originally involve glass greenhouses, instead thermal masses, fruit walls, were utilized. These thermal fruit walls stored heat from the sun for nighttime use, and are installed with insulated mats rolled out over the glass covers during the night or cold weather; passive solar buildings in the true sense.

Kris deDeker recently posted up a nice exploration of the utilization of passively designed fruit walls that were highly utilized in urban farming up until the late 19th century in Europe.

Fruit Walls: Urban Farming in the 1600s

This labor-intensive practice required a deft, skilled hand for maintenance. But cheaper, less-labor-intensive produce was imported due to the railways eventually took over.

I understand, some of these passive farming practices are still used in Korea. And the Chinese use passive solar greenhouses that are heated year round with only solar energy. Of course performance will be predicated on the greenhouse design, the location (latitude), and on the local climate.

According to Kris, produce grown in a passive greenhouse industry would take up two to three times as much space to produce the same amount of food. But do we really need to be eating so much anyway? 

Another challenge is it is a best-practice is to have a CO2-level that is at least three times the level outdoors to increase crop yield. When no there is no CO2 byproduct from the combustion of fossil fuel based heating systems inside the greenhouses, another source is required. Provided a structure is well insulated, compost from the manure of livestock and fish in an aquaponics system can serve this purpose. A compost heat recovery system producing hot water could be pumped through a radiant floor. So compost can serve a triple purpose; CO2 production,  heating, and soil enrichment.

Talk about a GREAT food propagation practice to re-institute in the urban environment. Get me to a warehouse space!

Fruit Wall Greenhouse

Greenhouse built against a serpentine fruit wall. Source: Rijksdienst voor het culturele erfgoed. http://ow.ly/Wm8qn

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