30 Nov Behold, The Walipini
Amidst the sad impending risk on about seven million people in Uganda due to the persistent drought amongst other consequences of climate change that could potentially raze Africa to the ground, a white smoke emerges from the sustainability chamber. Actually this happened 20 years ago, when the Walipini was first developed and deployed in South and Central America. The word ‘Walipini’ comes from the Aymara Indian language and means ‘a place of warmth’; now that’s a fun fact before we delve into the cooler stuff.
In summary, the ingenuity of the Walipini is that it is an underground greenhouse hence it is more cost effective to build as all you need is to carve out the walls and the floor of your greenhouse from the ground. The Walipini utilizes nature’s resources to provide a warm, stable, well-lit environment that could sustain year-round vegetable production. So how exactly is a Walipini unique to achieve these conditions? Simple. It has to be 1,8 -2,5 metres beneath the ground and is able to capture and store daytime solar radiation. Well, considering quite a number of African countries lie within the tropics, the aim would probably be the opposite with more insulation being used to keep away excess radiation from the overheard sun in the months of December, June, March and September. But before we carry on with any further amends, here’s roughly how it works.
The Walipini is kept insulated via a double layer of plastic sheeting (glazing) and the sealed dead air between the exterior and interior plastic sheeting which is 0,2 to 1,3 metres thick. The inside sheeting also keeps the inside humidity from penetrating and rotting the wooden poles spanning the roof. Another interesting characteristic is the fact that the angle of roof to sun has to be taken into consideration to ensure that the greenhouse receives maximum solar radiation with no obstructions such as buildings or huge trees nearby. The objective of the roof is to maintain a 90 degree angle between the Walipini roof and the afternoon sun during maximum solar radiation.
All in all, this is why a Walipini should be your next cool project:
- Visually appealing. This is definitely relative but we can all agree that it does not take up as much visual space on the landscape.
- Effective in almost any climate. Walipinis and other pit-style greenhouses are nearly effective and efficient everywhere. Alterations could occur in terms of materials used but the concept and results are within the same spectrum.
- Less maintenance. This is majorly in comparison to the traditional greenhouses which are completely exposed to the elements thus subject to wear and tear.
- Versatile in its use. Despite the conventional vegetable growing, underground greenhouses could also be built to accommodate livestock especially those that are cold-sensitive.
- Protection from chemicals and pests. With Walipinis, it is nearly impossible for most chemicals and pests to get onto your produce especially those transmitted by wind or other animals.
Takes advantage of thermal mass. When you dig down even just four feet, the temperature changes dramatically. Because underground greenhouses are warmed by thermal mass on all sides(by the soil), you can’t really lose any warmth compared to a traditional greenhouse.