Polytunnel

A polytunnel is a tunnel made of polyethylene, usually semi-circular, square or elongated in shape. The interior heats up because incoming solar radiation from the sun warms plants, soil, and other things inside the building faster than heat can escape the structure. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. Temperature, humidity and ventilation can be controlled by equipment fixed in the polytunnel.

The idea temperature in the polytunnel is between 23º and 25º. At higher temperatures the fungus will grow and attack the plants.

Apart from special equipment we can modify the temperature and the humidity inside the polytunnel using very simple techniques.

To lower the temperature we can:

- Paint the glasses in white to

- Open the doors

To raise the temperature we can:

- Put the blinds in the evening

- Place a reflecting blanket

- Use a propane burner

- Place hot-water pipes

- Place red lamps

If we are building a green house we can build the south face with brick as it will retain the heat inside them and the north side with stone to avoid loosing the temperature on that side.

If we need to lower the humidity inside the polytunnel we will open both ends of the tunnel to circulate the air.