An ecological, inexpensive and healthy earth and bamboo house

This is our latest construction ! One bedroom, one living room and a bathroom fit in only 44 sqm in the middle of a bamboo plantation near a pond. We wanted to build a small and cozy house using as much as possible natural, locally sourced or reused, inexpensive materials. It also integrates elements of bio-climatic design to allow passive cooling and avoid air-conditioning. The end of construction is planned for October 2020. The project was slowed down during 3 months due to Covid 19 lockdown, and has been suspended during July and August as we expect heavy rain.

Many thanks to the people involved in the construction: Fon (for taking care of people and preparing delicious meals), talented local workers (Long Kwan, Pee Waeng, Peesee), workshop participants and volunteers (Damian, Sonam, Gael, Simon, Natanael, Etienne, Carole, Andrea, Israel, Irene, Cécile, Yohann, Santiago, Michaela, Samuel, Mathias, Audrey, Naro) and our friend Philippe.

Inexpensive

Estimated cost: 90,000 Thai bahts (2,600 euros, 2,900 USD) (Materials: 50%; Food for volunteers & workshops participants: 30 %; Labour (local workers) 20%).

From the design stage, we planned to limit the cost without affecting the strength, durability, reliability and maintenance by using:

  • earth obtained after digging our pond to make the walls
  • cheap local products (rice straw, rice husk, special grass for thatch roof)
  • bamboo canes mostly from our land
  • reclaimed windows

Ecological 

We mostly used locally sourced natural materials to reduce the carbon footprint. Efforts were made to minimize the use of cement (gravel bags and rubble rocks for the foundations). The thatch roof of the yurt is also environmentally friendly, however it will require to be changed every 4-5 years due to possible damage from the weather and insects.

In some cases it is hard to avoid using materials  that are either non-natural or with a rather high carbon foot print such as:

  • bedroom roof made of metal sheet aimed to be more long-lasting and maintenance-free than other natural options such as leaves, thatch, bamboo etc
  • metal structure is more reliable and long-lasting than most timber and bamboo that might be damaged by termites (although teak wood might have been used).

In addition, unfortunately, it becomes more and more difficult to find local skilled workers who are able to complete tasks using natural materials and ancient building techniques. Labour costs and the need for future maintenance must also be taken in to account.

Healthy

Another advantage of building with natural material is to avoid hazardous building materials, toxic paint, thinner, insulating materials etc

The construction…

Living room

In October 2019, we started to build a yurt out of bamboo. It was installed on a rubble rocks foundation to limit expenses and avoid using cement. 60 bamboo canes were assembled with strong ropes, treated with non-toxic chemicals (boric acid and borax) to protect them against insects. The roof structure is made of 14 strong treated bamboo poles, tight to the central steel crown (toono). The roof cover is made of local thatch (‘yakaa’), light, cheap and acting as insulating and waterproof roof.

The walls are partially covered  with earth using a technique adapted from the ancient ‘wattle-and-daub’ method. Split bamboo canes are placed horizontally, weaved between the yurt canes. Then an earth mix (earth, sand and straw) is put around the split bamboo.

Bedroom

It started in December 2019, as an extension of the yurt. We wanted to make strong load-bearing earth walls for a 20 sqm bedroom. We chose to make the walls by using 3 methods in order to allow workshop participants to practise several techniques: Adobe bricks, Cob and Earth Bags.

Drainage and foundation: rubble trench and three layers of bags filled with gravel.

Walls: Adobe (earth bricks dried in the sun), Cob, Earth bags using earth, sand and straw

Roof: steel structure and metal sheet. For a better insulation, a double-roof made out of bamboo frame and climbing plants will be installed.

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Shower

Outdoor shower will be simple: bamboo for the walls and small stones for the floor.

Passive cooling design and techniques

To prevent or reduce heat, and – of course – without using air conditioning, we designed the house using the following strategies:

Shade: the rooms will be shaded by the surrounding bamboo a few hours in the day. Besides, the two rooms have a overhanging roof.

Thermal mass: The thick earth walls (40 cm, 16 inches) of the bedroom, combined with several openings will help to cool down the interior during day time. The heat is stored during hot hours then released during the night and the openings help the warm air to escape.

Insulated roof: the thatched roof of the living room provides good insulation. Above the central toono a gap between the roof and its top ‘hat’ helps the hot air to escape.

double roof

Double-skin roof: An outer roof made of a bamboo frame and climbing plants will be installed above the inner metal sheet roof, with a 40 cm gap between the two rooves. The roof system will then be naturally ventilated by natural convection (air flow).

Thermal buffer: One side of the bedroom is facing the south and is too thin (5 cm) to benefit from thermal mass. Instead of improving the insulation, we chose to install a pergola with a bamboo roof and climbing plants to reduce the heat in the bedroom.