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Clever Rocky Mountain Greenhouses Give Major Season Extension

In cool and cold areas the length of the growing season and the cold temperatures are the main challenge for growing things and supporting oneself. As part of the search for cold climate permaculture strategies I came across integrated greenhouse designs that seem to have a lot to offer to us in the cool climates. This is a little report from a trip to the Central Rocky Mountain Permaculture Institute‘s solar greenhouse workshop in Basalt, Colorado. There, during his thirty five years of living on the site, Jerome Osentowski the director at CRMPI, has overcome the challenges of his steep sloping land at 2,200 meters above sea level with advanced integrated greenhouse designs as a feature in the overall system. They have stretched his climatic zones all the way to the subtropic – all year round, with no fossil fuels used.

Conventional greenhouse growers spend immense amounts of money and oil or natural gas to heat the greenhouses during winter whereas in Jerome’s greenhouses the heating is powered with a couple of 90 Watt fans – equivalent to the old light bulbs. They run his Subterranean Heating and Cooling System, SHCS, aka "climate battery" which utilises the excess heat produced in the greenhouse in the middle of the day and during summertime when air temperature exceeds ground temperature and stores it underground by a ventilation system. Conventional systems vent the air outside losing it as a potential heating resource. This way he is able to grow everything from winter greens to bananas and papayas and figs with minimal energy inputs at his site. "This fig is twenty years old now. We’re eating fresh fruit from it four months a year" he explains in the mediterranean greenhouse which is attached to the main house (picture inset).

There are four greenhouses at the site, which demonstrate three different climatic zones – warm temperate, mediterranean and subtropical. Two of them are integrated directly into the living spaces which adds another beneficial quality to them – the heating season of the houses is reduced by several months every year. The biggest one, named Phoenix, is a 26×72 foot (8 x 22m) free standing unit and a subtropical food forest demonstration site.

The greenhouses are planned using integrated permaculture design, taking into account location and aspect, making the best use of the site’s sloping terrain, and including plenty of thermal mass and rainwater harvesting features. Phoenix is also building its own soil since the raised beds are simultaneously vermicomposting factories, where autumn leaves, coffee grounds from the local café and rabbit beddings from the yard turn into a fertile growing medium for the plants with very little human labor required.

The Subterranean Heating and Cooling System is a result of research and development done at CRMPI based on Jerome’s greenhouse work and John Cruickshank’s additional technology. Some of John’s work can be seen on, where the SHCS is explained. John has also worked with Michael Thompson and Jerome from EcoSystems Design to refine this technology.

So how does it all work? Under the soil layer there are several layers of plastic pipes buried into the ground, where air circulates from the greenhouse, controlled by a thermostat. In the hot season the fans draw warm air into the ground where the heat (and extra moisture, which helps control the negatives of an overly humid environment) is collected into the soil, and the cooled air is returned into the greenhouse. In the winter, when needed at nighttime, a different thermostat turns on the same fans, pulling the cooler air down into the warmer soil, warming the air and thus warming the greenhouse. The soil temperature stays constantly at +20°C which helps the plants tolerate potential frosts in the coldest winter nights when the temperature outside can drop all the way to -32°C. When there isn’t enough heat stored in the climate battery, Jerome and the interns heat up the sauna attached onto the north wall of Phoenix, and while maintaining their own health this way, the greenhouse plants are nurtured with warmth as well.

We visited CRMPI in May for a solar greenhouse design workshop and did some volunteer work for Jerome. It was indeed a unique feeling to curl up in a hammock after a lunch that we had harvested just earlier, and have a little nap on a chilly and rainy May afternoon listening to the drops hit the roof and watch the tomatoes ripen.


  1. I always heared the argument that here in Norway we have to import fresh fruit and vegetables during wintertime, because the transport generates less CO2 than growing it here. Maybe this is not a valid argument using this tecnuiqe?

    Still I guess one in Colorado have a large energy input from solar radiation during winter time, something we don’t have here, as the sun is below the horizon in winter time.

    1. Please note that the Vikings FARMED GREENLAND from about 800AD to 1200AD. This was not because of industrial sacking and pillaging. In the US there are studies showing that CO2 is greater near the cities and plants like burdock may grow to 14 feet tall (Baltimore) in that CO2 rich environment. The further you go into rural territories, the lower the CO2 levels, more normal the growth. Anthropogenic CO2 is NOT responsible for global warming – pretty much proven to increase water vapor which reduces the solar heating….
      Can you generate heat/electricity/lighting with a wood-powered generator? A vacuum to decrease distillation of water would be beneficial because distillation would take place at MUCH lower temperatures and the distilled water (recycle it) would save life on the equipment….

      That would/could provide heat, light, and perhaps excess energy. If you ran 12 volt, there are heating mats which are almost self-regulating that can be safely placed under flooring, (wood, tile, carpet even) and as the heat in them increases they reduce their efficiency and so the material itself can never initiate combustion. Would make a good solar system dump for excess energy, and i suspect an easy and simple bottom heating system for pots or springtime starts to transplant….

  2. Great greenhouses have given me much inspiration for extending seasons, and growing things out of region. Jerome’s spot is amazing. The subterranean heating and cooling seems to work well and I will be doing a workshop in fall 2010 in California.
    contact [email protected].

  3. Hmm. I once heard that in Iceland there exist greenhouses whose temperature is regulated with geothermal steam. I wonder if similar greenhouses exist in other countries. Also, it might be possible to produce the required amount of water vapor in a greenhouse, even in places where geothermal steam is not available. For instance, a greenhouse wherein steam is generated by an electrical boiler element can be employed for small-scale production of bananas and other plants that like muggy conditions.

  4. Marijtje, Colorado is as far south as Spain. But I’m sure with this system you can stretch the time significantly for when the CO2 accounting comes in favour for growing vegetables here in Norway.

    Unfortunately we do now use so much electrisity during the coldest time of winter that we have to import not renewable energy.

  5. I think in places like Finland (where I’m from) and Norway this kind of integrated greenhouse designs can at least remarkably extend the growing season and for example reduce need of heating the buildings, even if we can’t make it all the way to the subtropics with our limitations of available sunlight and long lasting cold periods.

    Jerome is coming to Finland to do a workshop on permaculture and greenhouse design this autumn, and hopefully we can get some pioneering projects happening to test how far we can go!

  6. See this link (in Scandinavian language):

    This guy, Per Vatne, has developed a technique to drill 10000 meters long holes in the ground, down to 15 cm in diameter. The interesting thing is that he can also drill deep u-shaped holes to harvest thermal energy from the ground.

    I see a future here where we can combine energy from the Earth with energy from the Sun. This way we could be able to produce all our food here in Scandinavia without significant amounts of CO2.

  7. It was really inspiring to visit Jerome and see what he has achieved. The implications are really amazing for areas that get enough light through the winter to keep things growing. In the far north where the amount of winter light becomes a limiting factor I am very interested to see how much the growing season can be extended…. without adding lights or other energy consumptive measures that overbalance the gains. But just think of all those saunas connected to a greenhouse!

  8. As founder of Colorado’s San Luis Valley Solar Energy Association I have been involved in low-cost, low-tech solar projects in 20 countries. I have a question regarding subsoil moisture-related problems due to recycling air through the earth batteries. I am working on using an active solar air heating system (see workshop under media/videos tab at the Heart Mind Alliance’s website) which uses outside dry air of New Mexico, heats it and then forces it into earth battery.
    Was a solution to the moisture-related algae and fungus, etc growth found?
    Thanks for feedback
    Bob Dunsmore

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