Simple wooded structures assembled from locally available materials Plate 11 Photo: W.O. Baudoin Figure 43 shows a saw-tooth construction with gutter. The roof consuruction consists of and surfaces. vertical sloped The vertical surfaces are open for ventilation. Saw-tooth face houses are relatively cheap. For maximum incidence of light, the vertical surfaces have to the sun in winter. If the vertical surface with the ventilation openings is placed away from the wind, the wind current leads to a negative pressure which sucks the warm air from the greenhouse. This can improve the ventilation efficiency. The sloped construction parts can also be built of flexible wood or bamboo sticks. The ventilation efficiency i good but problems can r in the installation of the gutters. The saw-tooth construction proved sensitive to wind forces in some countries.