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.

YouTube Preview Image