Thursday, February 8, 2018

Solar Pit Greenhouse

A "Pit" what???

A Pit Greenhouse utilizes nature’s resources to provide a warm, stable, well lit environment for year round vegetable production. Locating the growing area 6’- 8’ underground and capturing and storing daytime solar radiation are the most important principles in building a successful pit greenhouse.

A greenhouse can be built by digging a hole in the ground and covering it with glass. This takes advantage of the heat stored in the earth during the cold season (warmth in winter, cooling in summer). At the depth of a couple of meters, there is very little seasonal variation in temperature. The earth around the greenhouse structure has large thermal mass.

One of the main principles involves embedding the greenhouse in the earth to take advantage of the earth's constant temperature, to store the solar energy collected during the day.

The solar gain comes through a light-permeable material such as plastic, Visqueen, polycarbinate. The angle of the panels is designed to be 90-degrees to the Winter Soltace sun (Dec. 21 / June 21, depending on hemisphere). The upper portion of the walls are insulated down past the frost line.

~ Taken from Benson Agriculture and Food Institute Publication

This is our "completed" structure

A Pit Greenhouse ... sometimes called a Walipini, underground greenhouse, subterranean greenhouse, solar or passive solar greenhouse ...

After a great deal of research, the GesundheitsVerein decided that this would be our best option for year round operation.. We had the property and an existing house where we would attach the "pit". The area faced south for the best sun penetration and the water table was several meters down so no worry about flooding. The soil is extremely gravelly and has excellent drainage ... and as we found out during construction of the greenhouse it was a lot like concrete ... lol!

The solar "pit" greenhouse is completed, although we will always be tweaking it ... this earth friendly structure will allow us to grow crops using experimental means like vertical and container gardening all year long in the cold climate of Austria.

We began the middle of September 2013 and as anyone who has undertaken a project of any magnitude, you will know that it is taking longer than expected! Constructed by the members and working many long hours we finally were able to say that the first week of January 2014 we were "closed in"! Of course, there was still more to do ... that only means that we were protected from the outside elements ...

Follow along and watch as we complete this incredible project ... we began sprouting seedlings in January 2014 and during the early spring our plants growth began to explode!

Saturday, February 13, 2016

Tour the Pit Greenhouse Mid-May

It is May and the plants are thriving and waiting until the 1st of June to go outside.  Austria is notorious for having a freeze the last half of May ... they call it the Iceman!

Enjoy the Tour

Friday, February 12, 2016

Building a Pit Greenhouse - You Gotta Have Fun!

For a bit of comic relief and to share the fact that not all things go according to plan, we have the morning where we were locked out of the Pit ... the glass doors were locked and a piece of the polycarbonate had blown in front of the cellar door wedging itself into an impossible spot:

OOPS ... "Pit" Greenhouse Locked / Blocked

Then there was the day AL went shopping by himself ... imagine our surprise when he asked us to help "unload" the car!

Unloading & working with this was like wrestling a box of snakes!  It will be the passive geothermal heating & cooling system.  For our purpose it will probably be more efficient during the summer to help with cooling the greenhouse. This is close to 500 feet ... Scheesch!

Wrestling a Box of Snakes!