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Permaculture Green House Design in the Sub Tropics

photo 17Permaculture Green House Design in the Sub Tropics

 

This is the tale of the creation of a unique green house built by an English woman, volunteers and five Mayan men in the Yoga Forest in Guatemala, Lake Atitlan. This strange and wonderful place is focused on learning about sustainable living from your inner self (zone 0) and beyond. I am grateful to have worked there as the permaculture director for the last 10 months.

 

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The permaculture Green house

 

This green house is built in the challenging environment of the inner slopes of an extinct super volcano, with only steep slopes and gullies available we utilised the terrain by building across a ravine and stream to help with airflow and thermoregulation in this hot and humid environment. Bamboo forms the frame of this beautiful structure as it is highly durable and can withstand hurricanes and the battering of heavy rains.

What follows is the story and methods of how this artistic creation was designed and constructed by a group of indigenous Mayan men, volunteers and myself.

 

Problems

 

  1. The searing heat and temperature fluctuations
  2. The steep undulating terrain
  3. Hurricanes and strong winds
  4. The lack of sunshine due to an abundance of trees
  5. A low budget
  6. Remote location which Is hard to access
  7. My terrible Spanish language skills
  8. Trying to direct as a female in a country where women don’t do that.

The old green house

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This is the original green house it fluctuated in temperature dramatically, it got so hot all the plants wilted and was too small for all our plants.

The new green house design

photo 3 So with my creative mind which is addicted to beauty this is what I designed, please bear in mind this is my first architectural design besides chicken houses.

Initially the idea was a geodesic dome structure, in permaculture these structures seem as appealing to some daring designers as herb spirals are to the novice.

 

Solutions in design

 

The sides are open to allow good air circulation for cooling. The problem of the uneven terrain has been turned into a solution; it’s built across a gully and stream bed with two of the side walls composing of the mud banks. This has multiple functions, the mud walls act as thermal mass helping to regulate the temperature. The stream running underneath also facilitates convection improving air circulation and helping with cooling.

 

The green house is built into a valley with a large cliff sheltering it to the north, a hill to the west and east and a mountain to the west to shelter it from strong winds and hurricanes.

 

The lack of sunshine due to trees is be alleviated by felling and coppicing the trees and using them for fire wood or construction.

 

We used as much grown on site timber and off cuts as possible to cut costs and utilised volunteers where possible.

 

My terrible Spanish language skills were alleviated by a good sense of humour, utilising English and Spanish speakers as well as learning key words, diagrams and charades.

 

I alleviated the problem of being female in this role by proving I was just as hard working and dedicated as the men, and that I new my stuff. And most of all I would enlist the help of Charlie the site architect and the man who paid the wages to help enforce my instructions.

Work starts

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First thing we did was put 3 cedar posts on either side of the bank, we chose cedar as it lasts longer than most types of wood in this humid environment; we fixed them to  towers constructed with stones and cement. Then we drilled in lengths of metal rebar into the stones which where then drilled into the poles. Initially we sank the poles into the ground which was a bad idea because they would soon rot with all the rain. This way elevated above the ground and placed on rocks, prevents rotting of the wood from sitting water. This is a very important step!

We fixed side bars lengthways across these poles using wire and screws to hold them in place.

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Thank goodness humour is universal

 

This work was originally carried out by my self, volunteers and Noe (pictured above) the forest guardian and jack of all trades with a speciality in carpentry and pluming. Me and Noe argued over the next steps for the next two weeks of how the roof would work before a Spanish speaking volunteer finally allowed us to realise we where arguing the same point. Luckily we both have a good sense of humour! Otherwise I a­­m sure he would have fed me too the dogs if I hadn’t fed him to my worms first!

 

So after much deliberation we expanded our team so it wasn’t just Noe that had to listen to my endless non-sensical harassment.

The dream team

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Alberto on the left is a master carpenter and Francisco on the right can turn his hand to anything. I made more detailed plans and utilised the Spanish speaking volunteer to help me translate.

The floor plan

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This plan shows shelving, locations of support posts and the floor.

The side plan

side plan

The side view of the structure shows how it fits into the ravine, where the beams and posts go, including how the floor is supported with stone pillars, where the beams fit together and the dimensions.

 

A scale model

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This picture shows a scale model of the green house using clay and thin strips of bamboo to show how the roof would be supported using the central beam and tension from the weaving of the bamboo strips. Although it looks a bit silly it actually helped a lot, the tilt of the model was actually true to the final design, a compensation we needed to make for the shape of the ravine. This scale model also helped greatly with helping the rest of the team understanding what was to be achieved.

Preparing materials

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Herrason is making Bamboo strips which are used to weave the roof. He split the bamboo poles using a flat ended machete which he hammered down the centres using a lump of wood. Its important to use freshly cut green bamboo as it splits without breaking. This is giant Mexican bamboo.

 

Fine tuning materials

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To make the strips flexible the inner pith has to be removed, this is a satisfying process whereby you simply separate the pith from the skin by tapping the machete down in between the two layers. Then the pith comes of all in one strip.

 

The central support

photo 11In this picture you can see the central supporting beam, which was made by screwing several strips of bamboo together to make it strong enough to take the weight of the other poles. This was then fastened to two horizontal pieces of bamboo that went across the ravine, connecting the side and central poles that are now in place. The central pole you can see in this picture was originally placed there to hold the centre of the roof up whilst we constructed. It became obsolete as we realised the roof would have to be much higher if it was to support itself with dynamic tension as a result of its concave shape.

 

Beginning the weave

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The weave was originally planned to be in a six pointed star shape because its apparent ease of construction was matched by its aesthetic appeal. We first attached the strips long ways to each side beam using screws.

Weaving

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We made scaffolding using bamboo poles and ladders which were precariously placed over the ravine. Next the horizontal strips are threaded through. Then the diagonals as demonstrated by Gaspar in the for-front. This is a surprisingly tough process as the strips have to be woven in and out of each other and the curve of the roof means it requires a lot of force to pull them through. Gloves are necessary as the splinters are rife.

 

The floor supports

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The three pillars you can see in this image are preparations for the floor which is elevated above the stream. They are built on large boulders which are wedged deep into the stream bed and cemented to other larger rocks to stop them washing away when the rains come. The towers are then built up with rocks and cement after which a piece of rebar is drilled into them which will connect to a horizontal bar of cedar. This combination is crucial in wet and humid areas as it prevent water from sitting on the wood and rotting it.

The finished weave

photo 15This is the view of the top of the roof from the north side of the ravine, as you can see the stars didn’t manifest as well as planned as the dome shape made it very hard to manoeuvre the strips. However it’s very strong, strong enough to lie on. During the construction we soon realised that the dome wasn’t great enough for the roof to support its shape under dynamic tension so we added another two supporting beams made from several bamboo strips joined together.

The arches

photo 16This is a view of the side of the green house. The arches where created by a continuation of the design which was pulled down and then attached to another arched strip and held in place with screws. In this picture it shows the arch attached to a pole but this is only for aesthetics as the arches held themselves in position without needing to be pulled down.

The Grand finish

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This picture shows Alberto (the master carpenter) and I, looking proud with the roof finally finished. We chose an opaque plastic to cover it as it is more sun resistant than the clear plastic. Plastic such as this is at risk of becoming brittle if exposed to sunlight for long periods of time. After weeks of deliberation on the best methods of attaching it we finally decided upon the humble staple gun. The plastic was folded a few times before it was stapled in so that it did not tear easily. You can also see the floor supporting beams in this picture, consisting of three erect beams upon rock pillars which go towards the back on the inside of the Gully, then two supporting beams on the outside edges with horizontal beams on all sides which support the weight of the floor. The two diagonals don’t bare much weight and are more for effect.

view of the floor inside the green house

photo 18This picture shows one of our volunteers Angelica using the work bench. The green house has an amazing view over the forest and remains at a lovely cool temperature. The floor itself is made from Mexican bamboo which has been split and then hammered out flat. This is a cheap fast and effective method of making flooring. As you can imagine the openness of the green house leaves it vulnerable to butterfly attack, the tower of shelves to the right of this picture is a special seedling area with net curtains for those plants prone to caterpillars.

Happy gardeners

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Andres the ornamental gardener and I both happy the task is complete and we can finally get growing!

 

 

 

 

 

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